Also, don't hesitate to use 1.560 pistons to get your quench height when you can. It can eliminate the need to deck the block when the surface is good. I personally prefer the 1.560" over the 1.540" pistons in the 350 most of the time
@jessesyfie7244 Are you then saying the correct quench is, and must be no closer than .045? If so then I disagree. I have run many SBC at .035 on street engines (those running sub 6500 rpm). It is a better quench than .045 to combat detonation as long as the CR is not above what the octane rating can accommodate. Many of those engines when a thicker gasket is used will detonate even though the CR is decreased by the gasket thickness
@@bobnankervis9722 yes. .035 would be better than .045. If your willing to go that tight without pistons kissing the heads. I been shooting for no more than .040
Mr. Gold. I have seen a number of your videos and enjoyed each one. Please keep up the good work. About 20 years ago I hired my local engine rebuilding shop to do a complete performance rebuild of my 1977, 400 cid Pontiac engine. A stroker crank assembly from Eagle was installed which brought the displacement up to 461 cid. After the block was machined and the rotating assembly test fit, it was found that the pistons were 0.015" down in the block. The gasket compressed thickness was 0.039". Jim Hand, a well known Pontiac drag racer and performance enthusiast of the time, strongly recommended that I have the deck to piston clearence taken to 0.000". To your point, Mr. Hand stated that this would greatly improve the quench and reduce risk of detonation despite boosting the static compression ratio. I made this suggestion to the shop and as far as I know.....they diid it. I can tell you that this engine was broken in and tested over 20 times on their engine dyno and the engine ran very well. It still does.
Ben Alameda Racing does a great explanation of this also for those who are interested..👍🏻 Tight quench is a good thing all the way around for Na stuff. We like to see a shadow mark or witness mark where the piston almost just kisses the head.. No carbon build up, zero detonation less ignition timing and octane required and of course more power and better fuel economy. Win Win👍🏻
Great info. as usual, Alan. 20K Subscribers soon Congrats! Hope your healing process goes well. I've always used .030 min. quench for an engine w/ cast iron block and heads using steel rods and held to less than 7000 r.p.m. Add .005 for engines that would see over 7000 r.p.m. This always worked for me, providing max performance and no detonation, no run-on, etc. Some feel this is too tight. I'm just stating what worked best, without fail, for me. If the vehicle is manual or somehow over revs, no engine limiter, missed high r.p.m. shift, etc. these dimensions may not be adequate. Though I never had a problem since my race engines always incorporated a rev limiter. With aluminum components, aluminum rods, and over 7000 r.p.m. .040-.045 quench got the job done without issue. Also, as far as mitigating detonation and determining accurate compression make certain to include the crevice volume calculation. Crevice volume is the open space between the top ring and the bottom of the cylinder head or gasket...(Provided the gasket bore size is exactly the same size as the cylinders.) There are head gaskets that are manufactured with bore sizes larger than the actual cylinder bore dimension. If this type of gasket is used it can dramatically increase crevice volume if the head gasket is a thick one.
I`ve noticed when you buy garden variety oversize (.030) pistons they decrease the pin height by .020. to do exactly what us hotrod guys hate, keeping the compression low, but they will keep the pin height stock for an extra charge which we hate too. My dad told me "if you got a problem throw money at it and it will go away".
Great video Allan. Thanks a lot, I learned a _LOT_ from this video. Hard to believe after all the years of half-hearted hot rodding and standard street engine rebuilds how much I did not learn. Better late than never.
@@davestarr7112 people just don't get it they buy the cheap overhauled kits with pistons down the hole .045 and use the .040 gaskets and have a quench of .085 and them motors don't got shit for compression and wide quench , they denotation and they run worse than a stock engine and people dont have a clue when u explain stuff to them. I never buy the cheap rebuilt kits.
Hi Alan, spot on!, I try to explain this to certain clients, and when they use cams with inlet durations above 280 degrees it hurts compression drastically coupled to engines with excessively large quench. I have an old Keith Black piston catalogue and he explained the importance of proper quench and how smaller quench area improves detonation resistance.
@goldsgarage8236 Hi Alan, I'm definitely no expert! , I qualified as an Automotive Machinist 26 years ago, I guess building engines multiple different ways shows one what works and what doesn't. Regards, DC
Thanks very much ....great info.. I have always been told .060 was about as close as you wa ted to go with aluminum heads. I am running Indy l port worked aluminum W2 heads with a 2.100 intake valve on a 410 cub inch LA based 360. I admit I am a lifelong hotrodder but rookie engine builder.....always learning..... set up of everything correctly complements everything else. Great video.
I'm glad I noticed that the piston height was different, it changed how much I decked my 355. The pistons ended up .004 in the hole, my quench was .044 and compression was 9.87:1 With the XR264HR-10 it should be a fun motor for my daily driver Square Burb. I'll be putting it in any day now. Thanks Mr Gold for all the tips along the way
For the SBC I've found .035 to .045 quench works excellent especially with higher compression engines. Engines with aluminum rods require a bit more gap as the rods grow more in length when up to temperature. My rule of thumb is "if the pistons never contact the heads, the quench is not too tight". Of course if it is too tight, you'll find out the hard way! Lol
Theory- SQUISH Squish is when the gas in the Squish area is jetted out when the piston is coming up to TDC. It creates lots of turbulence, mixing, (and can make swirl etc) now you can have too much and blow the fire out. You can put the squish pad (s) so as to promote flow out the exhaust. Best to start with a modern head with a modern combustion chamber (hint they take less timing) most have quench/squish pads on both sides of the chamber and a central spark plugs Many early heads just copied the old "true wedge" designs from 48 Olds and Cad (and earlier) the 55 chey, 58 Chrysler etc. RUN pay up for a good head then add quench, One of my 440 Mopars has the pistons "+.015 due to deck twist which took lots of milling to get square (and Marine gaskets) .030 A 250 Chevy 6 with 307 TRW pistons profiled like the 350 "Turbo" piston ended up at .025 You can do it but takes some planning before you buy parts and deck the block. David Vizard has a video on quench and I see some others over in the suggested video listings You will have less timing and less octane strictures. I'm not saying you can't make slightly more power with an open chamber or hemi with race gas (but note the quench pads on late Hemis from most every make) Thanks POWELL great video
This episode really taught me a lot about the dark magic of quench. I never really under stood the importance of this until I found your channel ! I recommend your show to anyone interested in learning
I concur on the quench being too much. 0.040" is accepted as standard. Depending on the build, if it is a street oriented engine with decent steel rods and a 6500 RPM red line, the quench could be reduced some. 0.030" would be pushing it, but 0.035" could be beneficial. Stroke plays a big part as the longer stroke generates more inertial forces to stretch the rod and piston, especially as the RPM increases. Take it easy and get well Allan.
Thanks Dale, good point, piston speed is a function of stroke length. As for .030" remember, I have no control over what happens to an engine when it leaves my shop, so I have to be a little more conservative.AG
I commented about this project the other night in a lengthy post but if you are going to put in a rotating assembly then do your customer a real favor for about the same money and build him a 383. The increased torque and power will put a real smile on his face and no one will know except you and him. Personally if I were staying at 350 inches then just use the stock pistons if the bores are good without much taper. The TRW's are fine. After you clean them up they will look and work like a champ. Do a smooth bore finish and use some moly rings. If the deck height is .025 the use a steel shim gasket to get about .040 quench like they originally came with. Put a small roller cam in it and enjoy it.
You got it right Ag!👍🏻 Sbc likes a tight quench for max power. We go tight for both increased hp and detonation resistance.. I’ve seen them run at .020 with steel rods and some of the builders I know say they’ve went .018. Zero the deck and run a felpro. 039 and you’re wayyy safe. We run mls gaskets they’ll make them whatever thickness you’re looking for.
Forgive me if I didn't see it in other comments. Crevice volume above the top piston ring and around a head gasket bore that is more than needed can also lead to detonation. Much better burn potential as well. I recommend a Cometic gasket with the same bore size as your cylinder. It's probably not in the budget, but if you go with a 6 inch rod your piston choices gets better and you can get a ring package much closer to the top of the piston. Just things to think about. Cheers.
Another great video that's important to save. Thank you for the diagram, too, for detailed reference. Also A.G. my wife says you're handsome as well as a great presenter. :--) Thanks again and always appreciate your build insight.
AG just tore down my 357ci Cleveland last week. It had only travelled around 15,000kms and was tired. It had been built with 030 over pistons and a 050 compressed head gasket. Pistons were 036 down the hole, so 86 thou of quench. Did not work well at all. Full of carbon, would rattle with 24 deg total timing. Had the "good heads" on it ie: 302 Cleveland closed chamber 57cc. Measured in at 10: 1 static comp. Also had a very oversize head gasket with an average size of 4.150 inches. Very poor combination. Great content AG. Tim Australia 🇦🇺 ❤
Some theory, application below There are at least two things to consider QUENCH and SQUISH Quench is when two cold surfaces (the flat on the head and the flat on the piston-Think the Classic TRW "Turbo" Piston" and early Small block chevy. Or the PRE 68 Big Block Mopar and other "wedge" engines like Early Olds and Cad, Tough for detonation or ping to happen on the far side of the piston and the plug when clearance is held TIGHT
Excellent video Allan. Sorry to hear that you're temporarily laid up. I'm in the same boat as I just had surgery myself. Really interferes with work on the GTO. Thanks for the very informative video. Wishing you a speedy and complete recovery.
Always an interesting topic Mr. G. There's a recent thread on Speed-Talk discussing DCR and the also the merits of having proper quench. This is in regards to your typical SBC because as we all know, not all engine architecture is created equally. The quench was best described as a way of getting that mixture motion and moving those end gases which is where detonation typically starts. The part that stood out was the effect of higher octane fuels. It was described as a way of providing enough time to get those end gases consumed (due to it's slower burn rate) before compression temperature exceeded the threshold for self igniting. It would be worth noting the inlet air temperature is a key player here. Love your videos. Keep 'em coming.
Yeah, that jives with everything I've learned. I used a slightly different combination (for a slightly different application) to arrive at the same result. Good video. Take care of yourself, Allen. I'm getting old too. 😅
I like 1.56 compression height pistons, deck to 9.010 and run the GM .028 head gaskets. Skip White also sells pistons with a +.015 compression height = 1.575. More than one way to skin a cat...
When you mentioned that the pistons were .030 in the hole it reminded me of my last SBC build. My pistons were .050 in the whole and was going to be a lot cheaper to have the block decked than to round up another set with a better compression height.
I'm enjoying your videos and recommended them to my son! My 84 vette had the trw's and were only .022 in the hole. I'm using brodix IK 180 heads and am comcerned about now the "eyebrow' nelne relief enteracrs with those pistons
Thanks Gregg, if i understand your question, I believe that GM felt the valve relief design would help. As I recall, Z28 pistons were the same only with a raised dome.AG
@@goldsgarage8236 I will try to send the info from "chevrolet by the Numbers' It's said that the trw's in 84s were left over from the c3s. Thanks for the reply Allan!
One thing you need to remember about when the engine shuts down and diesel,s or runs backwards. Is the oil pump will also pump oil in reverse, so you are sucking the oil off the bearings when the engine runs backwards.
Thanks once again, you've got me thinking. In this type of application are quench and squish more or less the same thing and do domed pistons factor in if they are included in the mix?
Sure, quench and squish are both the distance or space between the flat part of the piston and flat part of the cylinder head. If you have a domed piston, you still measure from the flat surface, not the dome. AG
@@goldsgarage8236 Thanks for the reply AG. That's kind of what I figured. Just evil two-stroke thoughts messing with my head, where the effect is the same, but the visualization is different with no valves.
The "D" dish TRW Turbo piston is a good piston for HD use. I've bushed rods, offset ground cranks do whatever it takes to get your deck clearance. When tearing down your core check the deck clearance at all four corners before you pull the pistons I got involved with quench with the 413 Dodge Truck HD engines the ones with the plugs on top and a wedge chamber those motors worked better with quench. Other backgrounds were with our 62 Ramcharger and all the problem with the 13.5:1 compression without correct quench (too big a dome and not enough compression height and the spark plug down low in the side of the head, Why Mopar never used the 413 Truck style plug placement in the passenger cars is beyond me. 68 Mopar came out with the open chamber. Immediate problems with detonation with our STOCK car, We put the 67 closed chamber heads on till we got caught. Now some say the open chamber heads can make more power True at the very top end BUT you have to have race gas Never works on the street. We welded up the chambers then Had Nick Arias do some pistons with the head / domeraised to fill the open chamber Worked great but expensive We worked with John Erb at United ENgine and developed the quench dome hypereutectic pistons sold under the MT brand and now Icon. True Fact using these pistons and tight quench you can reduce your EGT by 800 degrees (and without the stock MOPAR smog cam with the long exhaust which gives an EGR effect) Do whatever it takes more if anyone is interested
I like the sound of that! I'm no engine shop, but I've tried a few things in my garage with the 2 mopars I've built. 383 - flat top pistons . I took off the 906 heads, and put on 516 heads with bigger valves, mild porting and smoothed chambers, steel shim head gasket. 10.0:1 cam 226@.050. Ceramic coated ports, chambers and exhaust valves. I almost can't get the engine to detonate on premium fuel with 30 deg base and 42 deg total timing (plus 18 Vac) It runs great in my truck. I'm dialling back the timing and trying running on Regular for the next couple months to see how it goes The other is a 360 which I used the stock heads, big valves and the UEM quench dome pistons (sold under Keith Black) I welded around the edge of the open chamber quench pad a bit to better contour with the piston quench dome (tighter squish). When I broke it in, the piston kissed the head where I had welded on 2 cylinders, and I had to reshape it a bit, so I guess I found the limit. I finished the cam break in on that afterwards but haven't done anything more with it yet. I'd love to hear more about your quench work on the mopars. Thanks!
Thanks Jm. Mopars sound complicated. I still have a 340 to do in the pipeline, you will be my go-to guy for advice when i get to it. Thanks for contributing to my channel. AG
@@goldsgarage8236 Is your 340 going to be a matching number restore or an open build If open build research heads Many late heads outperform even W2 Heads. A 360 is just a stroked 340 If you are getting a crank kit GO BIG and light pistons make it rev like a 302 chev do not bore any more than you absolutely have to with a stock block
@@goldsgarage8236 A little more planning on that 340 build. Do you want to run roller cam? If so sell the 340 to some matching number restore builder and get A: a late model roller 360 block or B get a 5.9 Magnum block. stroke either The Magnum (AMC designed) heads are much better than any LA head, almost as good as minor reworked W2 heads (better than most any SBC head even Vortec but not SB2) slap 340 looking valve covers on and brag about it. I'm a big Stroker McGurk fan on the street.
Yes it’s the distance between the flat part of the dome piston and the flat quench pad of the head. Tight quench is good as long as it’s not too tight..
Also I learned that most stock rebuilder pistons have around .020 shorter compression height to account for cutting the deck of the block. To me that seems excessive. Maybe .005 shorter would work just fine.
What's the stock deck n steel shim do for it like 55 guench??? Or I'm maybe 65. Im running 350 block eagle 375 crank short 400 rod n like DZ 302 pistons domed a .015 felpro steel n Dart 007 72 cc. Pocket ported n bowl work nothing eles. A GOOD tork cam 282 with retro roller n 1.6 rockers a air gap n 750 Brawler n A 1940 FORD PU 325 REAR 350 N KIT N A TCI BREAKAWAY CONVERTER TELL ME ABOUT THE FUN FACTOR PLEASE IS IT GONNA WORK OR NOT???
Yes Lance, the quench pad on the head lines up with the deck of the piston, that is where quench is measured. The dome protrudes into the combustion chamber. Hope this helps. AG
Todd, lots of variables to consider. I suggest you mock it up and measure the distance from the deck to the piston (deck height) before you go any further. AG
Whats the difference in price between using longer rods and pistons with suitable compression height and going standard length rods with decking the block as you say?
Thanks Magnus, 5.7" is the standard and they are typically less expensive. Even with 6" rods you still have to mange quench height as they require pistons with shorter compression height. The difference in length is only 5%. AG
Thanks for the question, no because 6" rods require pistons with the pin hole moved toward the deck (shorter compression height) to compensate for the .300" longer rod. As far as i know there are no commercially available rods with just "slightly longer" center distances. AG
0.030 is a typical target… tighter is better…. But touching can lead to a bad day. It’s important to measure. These are actual clearances. Tolerance stacking is the reason for wider targets.
@@trailerparkcryptoking5213 Less distance. Quench is technically an action. It means to suppress or extinguish a flame. The measureable amount of area which will accomplish this is less than .060" for an internal combustion gasoline engine.
Thanks James, glad you asked the question. It is more than I thought. With the .025" deck height and .015" gaskets, the CR is 10.15. With .045" deck height and .040" gasket, the CR would be 9.18. AG
Smokey Yunick used a double steel shim with a 0 deck. I don't think it matters as long as you get .035 to .045 deck height. But who I'm to argue with Smokey Yunick.
@ 5:58 Holy Mother of un burnt fuel and lazy Small Block Chevrolets.....0.080" quench! That thing was experiencing a lot of detonation from that grand canyon of piston to head clearance. I bet it was a COVID engine build! Had to be.....the piston was practicing mechanical distancing from performance.
That is definitely not ideal, 80 quench is really bad. I think 50 is about max I would ever go. GM recommends 35-45 thou. My 327 build is going to be 36 thou, 16 in the hole with 20 thou gasket. I had the crankshaft in my LS1 offset ground to get a tighter quench, thats a method I would only suggest if the crank is already getting turned..
Machinist that Prepped my block Polished crank and balanced my rotating assembly. Gave me a Print out with the numbers. I pay the big bucks Because he is a pro and I'm joe blow. I decided to buy the tools and double check. Can't figure out how he came up with his numbers. He say .002 out of the hole and it is -.004 in the hole. 2618 pistons. So it would have Grenaded. And he would have said it was me and I would have been 👌👈
Same here but with an old th350 trans had this shop do a stage 2 rebuild had a bad pan leak first thing lucky I took apart this thing was missing all the check balls and a couple springs that keep it quiet when shifting..never will go to a shop that claims way more than they can offer...
@jondough4116 I pay 1,700 and didn't have them Assemble. Hot tank, Balance rotating assembly, cut main caps, hone to 4.005 with deck plate. He was Supposed to deck. It's in the price, but sence it was close he didn't. Next time I will order a block from a cnc shop up north. Could have saved five hundred dollars and it would have been right more then likely. And wouldn't have taken 2 mouths. I thought about it after sending first message. It wouldn't have grenaded. It would have added .006 to Quench and piston to valve and lowered compression. But sence I'm at 11.1 with a .036 it would have Possibly been fine with the .o51 Gasket he Measured by. But the Quench would have been. 046-047
Thanks for the comments guys. i know it is frustrating. If you have no ability to measure, inspect or verify work, you are vulnerable. i do inspect and measure everything my MS (Atchison Machine in London Canada) does for me, but I have to say that their work is very precise and the quality is impeccable.AG
@@goldsgarage8236 Your welcome. But the flustrating part for me. Is not because I don't have a way to Measure. It's that the measurements are not right, it's that I grew up believing that a man says what he means And means what he says and stands behind his work. I should have been Amish. But Wearing the same thing every day and the same thing as every other guy and not having a mustache with my beard would be just too much. Lol
Standard "deck height" of a SBC is 9.000", not 9.025" Half of the stroke 3.480" = 1.740" 1.740" + 5.700" rod = 7.440" 7.440" + 1.560" compression height = 9.000" Factory blocks came with .025" to .030" of "meat" on the deck surface by design. It was to allow for future serviceability. They didn't know it was going to become the staple of production V8 engines throughout the world. They just knew at some point it was going to need to be rebuilt.
Deck height is what you make it, and it starts at approx 9.025" as Allen said, on a SBC, hence "standard (original) deck height". Compression height is 9.00" as you said. "Extra meat" on the other hand... well... I can't say I've heard that term before. Tomato/tomawto.
@@alleyoop1234 You need better sources. Standard deck clearance is 0.025" to 0.030" which brings the total deck height from 9.025" to 9.030", but that's not the spec of the block. Have you ever heard of someone "zero deck" a block? That's what they mean. Bring the surface of the deck down to 0.000" variance, ergo, within spec of 9.000".
Old Small block LA mopars always had an open chamber with zero quench. They should be horrible to tune, and make no hp/tq given your reasoning. In fact, tuning some high hp turbo combinations, your "quench pad " became an issue, and a source of spark knock. It isn't simple
Also, don't hesitate to use 1.560 pistons to get your quench height when you can. It can eliminate the need to deck the block when the surface is good. I personally prefer the 1.560" over the 1.540" pistons in the 350 most of the time
U have use .020 steel shim gaskets with 1.560 pin height pistons to get your correct quench! Or deck it .020 with .040 gaskets.
@jessesyfie7244 Are you then saying the correct quench is, and must be no closer than .045? If so then I disagree. I have run many SBC at .035 on street engines (those running sub 6500 rpm). It is a better quench than .045 to combat detonation as long as the CR is not above what the octane rating can accommodate. Many of those engines when a thicker gasket is used will detonate even though the CR is decreased by the gasket thickness
All good comments, thanks Guys.AG
@@bobnankervis9722 yes. .035 would be better than .045. If your willing to go that tight without pistons kissing the heads. I been shooting for no more than .040
Any quench distance less than .060" is adequate. You can go shorter but anything less than .060" is reaching the point of diminishing returns.
Mr. Gold. I have seen a number of your videos and enjoyed each one. Please keep up the good work. About 20 years ago I hired my local engine rebuilding shop to do a complete performance rebuild of my 1977, 400 cid Pontiac engine. A stroker crank assembly from Eagle was installed which brought the displacement up to 461 cid. After the block was machined and the rotating assembly test fit, it was found that the pistons were 0.015" down in the block. The gasket compressed thickness was 0.039". Jim Hand, a well known Pontiac drag racer and performance enthusiast of the time, strongly recommended that I have the deck to piston clearence taken to 0.000". To your point, Mr. Hand stated that this would greatly improve the quench and reduce risk of detonation despite boosting the static compression ratio. I made this suggestion to the shop and as far as I know.....they diid it. I can tell you that this engine was broken in and tested over 20 times on their engine dyno and the engine ran very well. It still does.
Thanks Sean. Your comment is a strong real life affirmation of the points i was trying to convey. Thanks for taking the itme.AG
Great stuff, you must have been a teacher in another life, great job.
Thanks Jan, nice compliment. I do enjoy it, or I wouldn't do it. I did teach night school at a community college in the early days. AG
Ben Alameda Racing does a great explanation of this also for those who are interested..👍🏻 Tight quench is a good thing all the way around for Na stuff. We like to see a shadow mark or witness mark where the piston almost just kisses the head.. No carbon build up, zero detonation less ignition timing and octane required and of course more power and better fuel economy. Win Win👍🏻
Ben is a smart guy, I watch his videos also.AG
Great info. as usual, Alan. 20K Subscribers soon Congrats! Hope your healing process goes well. I've always used .030 min. quench for an engine w/ cast iron block and heads using steel rods and held to less than 7000 r.p.m. Add .005 for engines that would see over 7000 r.p.m. This always worked for me, providing max performance and no detonation, no run-on, etc. Some feel this is too tight. I'm just stating what worked best, without fail, for me. If the vehicle is manual or somehow over revs, no engine limiter, missed high r.p.m. shift, etc. these dimensions may not be adequate. Though I never had a problem since my race engines always incorporated a rev limiter. With aluminum components, aluminum rods, and over 7000 r.p.m. .040-.045 quench got the job done without issue. Also, as far as mitigating detonation and determining accurate compression make certain to include the crevice volume calculation. Crevice volume is the open space between the top ring and the bottom of the cylinder head or gasket...(Provided the gasket bore size is exactly the same size as the cylinders.) There are head gaskets that are manufactured with bore sizes larger than the actual cylinder bore dimension. If this type of gasket is used it can dramatically increase crevice volume if the head gasket is a thick one.
All good info, thanks Bill. i have to take into consideration that i have no control over what happens to any engine once it leaves my shop.AG
I’d love to have you build an Olds for me. Your attention to detail is appreciated
Thanks Jimmy, Bring it to me and I will build it. I would love to do and Olds. AG
@@goldsgarage8236 that would be great!
I`ve noticed when you buy garden variety oversize (.030) pistons they decrease the pin height by .020. to do exactly what us hotrod guys hate, keeping the compression low, but they will keep the pin height stock for an extra charge which we hate too. My dad told me "if you got a problem throw money at it and it will go away".
Thanks Ed, your dad makes a good point. Higher compression height pistons are available, but they are expensive.AG
Great video Allan. Thanks a lot, I learned a _LOT_ from this video. Hard to believe after all the years of half-hearted hot rodding and standard street engine rebuilds how much I did not learn. Better late than never.
Thanks Dave, that is why we do it, Thanks for commenting.AG
@@davestarr7112 people just don't get it they buy the cheap overhauled kits with pistons down the hole .045 and use the .040 gaskets and have a quench of .085 and them motors don't got shit for compression and wide quench , they denotation and they run worse than a stock engine and people dont have a clue when u explain stuff to them. I never buy the cheap rebuilt kits.
Hi Alan, spot on!,
I try to explain this to certain clients, and when they use cams with inlet durations above 280 degrees it hurts compression drastically coupled to engines with excessively large quench.
I have an old Keith Black piston catalogue and he explained the importance of proper quench and how smaller quench area improves detonation resistance.
Thanks Dean, comments coming from an expert like you help to reinforce my point. Thanks for contributing.AG
@goldsgarage8236 Hi Alan, I'm definitely no expert! , I qualified as an Automotive Machinist 26 years ago, I guess building engines multiple different ways shows one what works and what doesn't.
Regards,
DC
Thanks very much ....great info.. I have always been told .060 was about as close as you wa ted to go with aluminum heads. I am running Indy l port worked aluminum W2 heads with a 2.100 intake valve on a 410 cub inch LA based 360. I admit I am a lifelong hotrodder but rookie engine builder.....always learning..... set up of everything correctly complements everything else. Great video.
Thanks G. I have never built an engine with aluminum rods, but .060" sounds reasonable. Its never too late to learn.AG
I'm glad I noticed that the piston height was different, it changed how much I decked my 355. The pistons ended up .004 in the hole, my quench was .044 and compression was 9.87:1
With the XR264HR-10 it should be a fun motor for my daily driver Square Burb. I'll be putting it in any day now. Thanks Mr Gold for all the tips along the way
Thanks Styxx, sounds like a nice street engine. Enjoy! AG
For the SBC I've found .035 to .045 quench works excellent especially with higher compression engines. Engines with aluminum rods require a bit more gap as the rods grow more in length when up to temperature. My rule of thumb is "if the pistons never contact the heads, the quench is not too tight". Of course if it is too tight, you'll find out the hard way! Lol
Thanks Bob, like flying too close to the sun! There is a safe limit to almost everything.AG
Theory- SQUISH
Squish is when the gas in the Squish area is jetted out when the piston is coming up to TDC. It creates lots of turbulence, mixing, (and can make swirl etc) now you can have too much and blow the fire out. You can put the squish pad (s) so as to promote flow out the exhaust. Best to start with a modern head with a modern combustion chamber (hint they take less timing) most have quench/squish pads on both sides of the chamber and a central spark plugs Many early heads just copied the old "true wedge" designs from 48 Olds and Cad (and earlier) the 55 chey, 58 Chrysler etc. RUN pay up for a good head then add quench, One of my 440 Mopars has the pistons "+.015 due to deck twist which took lots of milling to get square (and Marine gaskets) .030 A 250 Chevy 6 with 307 TRW pistons profiled like the 350 "Turbo" piston ended up at .025
You can do it but takes some planning before you buy parts and deck the block. David Vizard has a video on quench and I see some others over in the suggested video listings You will have less timing and less octane strictures. I'm not saying you can't make slightly more power with an open chamber or hemi with race gas (but note the quench pads on late Hemis from most every make) Thanks POWELL great video
Lots of good information Jm, thanks for contributing.AG
This episode really taught me a lot about the dark magic of quench. I never really under stood the importance of this until I found your channel ! I recommend your show to anyone interested in learning
Nice compliment, thanks Bob.AG
I concur on the quench being too much. 0.040" is accepted as standard. Depending on the build, if it is a street oriented engine with decent steel rods and a 6500 RPM red line, the quench could be reduced some. 0.030" would be pushing it, but 0.035" could be beneficial. Stroke plays a big part as the longer stroke generates more inertial forces to stretch the rod and piston, especially as the RPM increases.
Take it easy and get well Allan.
Thanks Dale, good point, piston speed is a function of stroke length. As for .030" remember, I have no control over what happens to an engine when it leaves my shop, so I have to be a little more conservative.AG
I commented about this project the other night in a lengthy post but if you are going to put in a rotating assembly then do your customer a real favor for about the same money and build him a 383. The increased torque and power will put a real smile on his face and no one will know except you and him. Personally if I were staying at 350 inches then just use the stock pistons if the bores are good without much taper. The TRW's are fine. After you clean them up they will look and work like a champ. Do a smooth bore finish and use some moly rings. If the deck height is .025 the use a steel shim gasket to get about .040 quench like they originally came with. Put a small roller cam in it and enjoy it.
Thanks for your suggestions Mike. I will comment on the 383 upgrade in a future video, many commenters agree with you.AG
Wish you a speedy recovery Mr. Gold
Thanks Hannibal, it is coming along nicely. AG
You got it right Ag!👍🏻 Sbc likes a tight quench for max power. We go tight for both increased hp and detonation resistance..
I’ve seen them run at .020 with steel rods and some of the builders I know say they’ve went .018. Zero the deck and run a felpro. 039 and you’re wayyy safe. We run mls gaskets they’ll make them whatever thickness you’re looking for.
Thanks Phil, i think there are "diminishing returns" for everything, even quench. i will play it safe with the .040" AG
@ It will be a whole different animal than it was that’s for sure Alan!👍🏻 Keep up the good work man , always enjoy you videos!
Forgive me if I didn't see it in other comments. Crevice volume above the top piston ring and around a head gasket bore that is more than needed can also lead to detonation. Much better burn potential as well. I recommend a Cometic gasket with the same bore size as your cylinder. It's probably not in the budget, but if you go with a 6 inch rod your piston choices gets better and you can get a ring package much closer to the top of the piston. Just things to think about. Cheers.
All good information, thanks for commenting Comet.AG
Put that engine on the dyno when it is done love to see what that thing can do with old school heads
Thanks Mika, we have to give Paul time to think about it. I would sure like to. AG
Another great video that's important to save. Thank you for the diagram, too, for detailed reference. Also A.G. my wife says you're handsome as well as a great presenter. :--) Thanks again and always appreciate your build insight.
Thanks Nys, please tell your wife i am blushing! AG
AG just tore down my 357ci Cleveland last week. It had only travelled around 15,000kms and was tired. It had been built with 030 over pistons and a 050 compressed head gasket. Pistons were 036 down the hole, so 86 thou of quench. Did not work well at all. Full of carbon, would rattle with 24 deg total timing. Had the "good heads" on it ie: 302 Cleveland closed chamber 57cc. Measured in at 10: 1 static comp. Also had a very oversize head gasket with an average size of 4.150 inches. Very poor combination. Great content AG. Tim Australia 🇦🇺 ❤
Welcome Tim from Australia. Great comments and sounds similar to what I found in Paul's engine. You know what to do! AG
Allen! You really should do a... live youtube show!!!
You have so much knowledge that your subscribers will increase exponentially @
Thanks for the suggestion Kevin. i will put some thought into how to do that. Thanks for the encouragement. AG
Hope you feel better soon your knolegable videos are greatly appreciated stay strong and keep up the great work you
Thanks for commenting Eddie. I am healing nicely, back to work next week. AG
Another informative video Allen, thx. I guess achieving proper quench with a dished piston is impossible.
Good point Dave. Probably true with the old smog pistons, but performance pistons now do have a quench pad to align with the head.AG
Some theory, application below
There are at least two things to consider QUENCH and SQUISH
Quench is when two cold surfaces (the flat on the head and the flat on the piston-Think the Classic TRW "Turbo" Piston" and early Small block chevy. Or the PRE 68 Big Block Mopar and other "wedge" engines like Early Olds and Cad, Tough for detonation or ping to happen on the far side of the piston and the plug when clearance is held TIGHT
Thanks for the info Jm.AG
Always informative
Thanks Brad. AG
Everything you put out is interesting and helpful to me. I love to learn new ideas that I will adapt to my builds. Thank you
Thanks for watching and commenting Ronnie. Glad you are finding it helpful. AG
Excellent video Allan. Sorry to hear that you're temporarily laid up. I'm in the same boat as I just had surgery myself. Really interferes with work on the GTO. Thanks for the very informative video. Wishing you a speedy and complete recovery.
Wishing you a speedy recovery also Todd. Thanks for commenting as always. AG
Always an interesting topic Mr. G. There's a recent thread on Speed-Talk discussing DCR and the also the merits of having proper quench. This is in regards to your typical SBC because as we all know, not all engine architecture is created equally. The quench was best described as a way of getting that mixture motion and moving those end gases which is where detonation typically starts. The part that stood out was the effect of higher octane fuels. It was described as a way of providing enough time to get those end gases consumed (due to it's slower burn rate) before compression temperature exceeded the threshold for self igniting. It would be worth noting the inlet air temperature is a key player here. Love your videos. Keep 'em coming.
Thanks as always Kevin for your support, and excellent technical description of a phenomenon that few people understand. AG
Yeah, that jives with everything I've learned. I used a slightly different combination (for a slightly different application) to arrive at the same result. Good video. Take care of yourself, Allen. I'm getting old too. 😅
Thanks as always 100, were all getting older and it sucks.AG
I like 1.56 compression height pistons, deck to 9.010 and run the GM .028 head gaskets. Skip White also sells pistons with a +.015 compression height = 1.575. More than one way to skin a cat...
Thanks Jesse, Sounds like you have it figured out. The Skip White pistons are an option, but not inexpensive and don't come in Eagle rotating kits.
Good stuff thank you
Thank you Darry! AG
When you mentioned that the pistons were .030 in the hole it reminded me of my last SBC build. My pistons were .050 in the whole and was going to be a lot cheaper to have the block decked than to round up another set with a better compression height.
Thanks Robert, true, but there is a limit to how far you can go with decking. AG
I think you are correct AG. The fuel travels across the piston and gets trapped with a quench area that is too big and burns a second time I think.
Thanks Don, that is a pretty good description of what happens.AG
I'm enjoying your videos and recommended them to my son! My 84 vette had the trw's and were only .022 in the hole. I'm using brodix IK 180 heads and am comcerned about now the "eyebrow' nelne relief enteracrs with those pistons
Thanks Gregg, if i understand your question, I believe that GM felt the valve relief design would help. As I recall, Z28 pistons were the same only with a raised dome.AG
@@goldsgarage8236 I will try to send the info from "chevrolet by the Numbers' It's said that the trw's in 84s were left over from the c3s. Thanks for the reply Allan!
Cool! Thanks man !
Thanks for commenting Bill.AG
One thing you need to remember about when the engine shuts down and diesel,s or runs backwards. Is the oil pump will also pump oil in reverse, so you are sucking the oil off the bearings when the engine runs backwards.
Thanks Racer, that is a really good point that I never thought about. We are always learning.AG
Get well soon
Thanks James, coming along nicely, planning to play hockey again next week.AG
Thanks once again, you've got me thinking.
In this type of application are quench and squish more or less the same thing and do domed pistons factor in if they are included in the mix?
Sure, quench and squish are both the distance or space between the flat part of the piston and flat part of the cylinder head. If you have a domed piston, you still measure from the flat surface, not the dome. AG
@@goldsgarage8236 Thanks for the reply AG. That's kind of what I figured. Just evil two-stroke thoughts messing with my head, where the effect is the same, but the visualization is different with no valves.
So, the old small block Mopar with a completely open chamber, no squish, should be a disaster and make no power right?
Sorry, I am not familiar wit them. Is that a mid 1970's smog engine? AG
I have .040 quench and my pistons are covered on carbon. What would cause that?
The "D" dish TRW Turbo piston is a good piston for HD use. I've bushed rods, offset ground cranks do whatever it takes to get your deck clearance. When tearing down your core check the deck clearance at all four corners before you pull the pistons
I got involved with quench with the 413 Dodge Truck HD engines the ones with the plugs on top and a wedge chamber
those motors worked better with quench. Other backgrounds were with our 62 Ramcharger and all the problem with the 13.5:1 compression without correct quench (too big a dome and not enough compression height and the spark plug down low in the side of the head, Why Mopar never used the 413 Truck style plug placement in the passenger cars is beyond me.
68 Mopar came out with the open chamber. Immediate problems with detonation with our STOCK car, We put the 67 closed chamber heads on till we got caught.
Now some say the open chamber heads can make more power True at the very top end BUT you have to have race gas
Never works on the street. We welded up the chambers then Had Nick Arias do some pistons with the head / domeraised to fill the open chamber Worked great but expensive We worked with John Erb at United ENgine and developed the quench dome hypereutectic pistons sold under the MT brand and now Icon. True Fact using these pistons and tight quench you can reduce your EGT by 800 degrees (and without the stock MOPAR smog cam with the long exhaust which gives an EGR effect)
Do whatever it takes more if anyone is interested
I like the sound of that! I'm no engine shop, but I've tried a few things in my garage with the 2 mopars I've built. 383 - flat top pistons . I took off the 906 heads, and put on 516 heads with bigger valves, mild porting and smoothed chambers, steel shim head gasket. 10.0:1 cam 226@.050. Ceramic coated ports, chambers and exhaust valves. I almost can't get the engine to detonate on premium fuel with 30 deg base and 42 deg total timing (plus 18 Vac) It runs great in my truck. I'm dialling back the timing and trying running on Regular for the next couple months to see how it goes The other is a 360 which I used the stock heads, big valves and the UEM quench dome pistons (sold under Keith Black) I welded around the edge of the open chamber quench pad a bit to better contour with the piston quench dome (tighter squish). When I broke it in, the piston kissed the head where I had welded on 2 cylinders, and I had to reshape it a bit, so I guess I found the limit. I finished the cam break in on that afterwards but haven't done anything more with it yet. I'd love to hear more about your quench work on the mopars. Thanks!
Thanks Jm. Mopars sound complicated. I still have a 340 to do in the pipeline, you will be my go-to guy for advice when i get to it. Thanks for contributing to my channel. AG
@@goldsgarage8236 Is your 340 going to be a matching number restore or an open build If open build research heads Many late heads outperform even W2 Heads. A 360 is just a stroked 340 If you are getting a crank kit GO BIG and light pistons make it rev like a 302 chev do not bore any more than you absolutely have to with a stock block
@@goldsgarage8236 A little more planning on that 340 build. Do you want to run roller cam? If so sell the 340 to some matching number restore builder and get A: a late model roller 360 block or B get a 5.9 Magnum block. stroke either The Magnum (AMC designed) heads are much better than any LA head, almost as good as minor reworked W2 heads (better than most any SBC head even Vortec but not SB2)
slap 340 looking valve covers on and brag about it. I'm a big Stroker McGurk fan on the street.
Is quench as important for dome pistons,should quench be in same tolerance as flatops
Yes it’s the distance between the flat part of the dome piston and the flat quench pad of the head. Tight quench is good as long as it’s not too tight..
Correct, thanks for commenting.AG
Also I learned that most stock rebuilder pistons have around .020 shorter compression height to account for cutting the deck of the block. To me that seems excessive. Maybe .005 shorter would work just fine.
Thanks Robert. I do not understand why they do that. If they made them .020" longer instead, i wouldn't have to deck this block. AG
Would you still deck the block if you were using dome pistons (11:1)?
What's the stock deck n steel shim do for it like 55 guench??? Or I'm maybe 65. Im running 350 block eagle 375 crank short 400 rod n like DZ 302 pistons domed a .015 felpro steel n Dart 007 72 cc. Pocket ported n bowl work nothing eles. A GOOD tork cam 282 with retro roller n 1.6 rockers a air gap n 750 Brawler n A 1940 FORD PU 325 REAR 350 N KIT N A TCI BREAKAWAY CONVERTER TELL ME ABOUT THE FUN FACTOR PLEASE IS IT GONNA WORK OR NOT???
A 30 inch tall tire 15 inch wheels
2800 lbs
Yes Lance, the quench pad on the head lines up with the deck of the piston, that is where quench is measured. The dome protrudes into the combustion chamber. Hope this helps. AG
Todd, lots of variables to consider. I suggest you mock it up and measure the distance from the deck to the piston (deck height) before you go any further. AG
Whats the difference in price between using longer rods and pistons with suitable compression height and going standard length rods with decking the block as you say?
Thanks Magnus, 5.7" is the standard and they are typically less expensive. Even with 6" rods you still have to mange quench height as they require pistons with shorter compression height. The difference in length is only 5%. AG
if you're going to do a rotating assembly mind as well just do a 383.
Thanks for the suggestion.AG
Hear hear, stroker!
Does crank and rod bearing thickness factor into the total piston height measurement in relation to deck height?
Thanks for the question. No, because we are measuring form centerlines. AG
In regards to deck height, are slightly longer con rods not a viable alternative to reduce quench?
Thanks for the question, no because 6" rods require pistons with the pin hole moved toward the deck (shorter compression height) to compensate for the .300" longer rod. As far as i know there are no commercially available rods with just "slightly longer" center distances. AG
Now do a video on "soft " chambers...
Hello Allan
I have a Ford 347 Windsor stroker, zero decked and 0.047 compressed thickness gasket.
Is it a acceptable quench?. 🙂
0.030 is a typical target… tighter is better…. But touching can lead to a bad day. It’s important to measure. These are actual clearances. Tolerance stacking is the reason for wider targets.
Thanks 59. Sure, I think .047" will work fine. AG
@@goldsgarage8236 Thank you Allan 👍🙂
How come you don’t use a 6.0 inch rod instead of the 5.7
A 6" rod requires a piston with a shorter quench height, so it doesn't really change anything. You still have to manage it. AG
Less quench or less quench distance?
Less quench distance.AG
@@trailerparkcryptoking5213
Less distance. Quench is technically an action. It means to suppress or extinguish a flame. The measureable amount of area which will accomplish this is less than .060" for an internal combustion gasoline engine.
So what's the change in compression ratio?
Thanks James, glad you asked the question. It is more than I thought. With the .025" deck height and .015" gaskets, the CR is 10.15. With .045" deck height and .040" gasket, the CR would be 9.18. AG
Smokey Yunick used a double steel shim with a 0 deck. I don't think it matters as long as you get .035 to .045 deck height. But who I'm to argue with Smokey Yunick.
Me too! thanks for the info Joe.AG
@ 5:58 Holy Mother of un burnt fuel and lazy Small Block Chevrolets.....0.080" quench! That thing was experiencing a lot of detonation from that grand canyon of piston to head clearance.
I bet it was a COVID engine build! Had to be.....the piston was practicing mechanical distancing from performance.
Thanks Arturo, I got a good chuckle from your comment. Levity is good. AG
@goldsgarage8236 keep up the good work Gold
What steel sbc head are you using on this build?
Cast# 292 angle plug heads.
Correct, thanks MJ. Note that the heads are cast iron. AG
The experts say, if your quinch is not correct, get rid of it.
Thanks David.AG
That is definitely not ideal, 80 quench is really bad. I think 50 is about max I would ever go. GM recommends 35-45 thou. My 327 build is going to be 36 thou, 16 in the hole with 20 thou gasket. I had the crankshaft in my LS1 offset ground to get a tighter quench, thats a method I would only suggest if the crank is already getting turned..
Thanks Jeffery. Grinding the crank offset is I method I have never seen, and correct, it only works if you have to grind it anyway.AG
Machinist that Prepped my block Polished crank and balanced my rotating assembly. Gave me a Print out with the numbers. I pay the big bucks Because he is a pro and I'm joe blow. I decided to buy the tools and double check. Can't figure out how he came up with his numbers. He say .002 out of the hole and it is -.004 in the hole. 2618 pistons. So it would have Grenaded. And he would have said it was me and I would have been 👌👈
Same here but with an old th350 trans had this shop do a stage 2 rebuild had a bad pan leak first thing lucky I took apart this thing was missing all the check balls and a couple springs that keep it quiet when shifting..never will go to a shop that claims way more than they can offer...
I went further after opening pan up inside pan was filthy and full of grey shit that's when I found more things wrong...2k rip off..
@jondough4116 I pay 1,700 and didn't have them Assemble. Hot tank, Balance rotating assembly, cut main caps, hone to 4.005 with deck plate. He was Supposed to deck. It's in the price, but sence it was close he didn't. Next time I will order a block from a cnc shop up north. Could have saved five hundred dollars and it would have been right more then likely. And wouldn't have taken 2 mouths. I thought about it after sending first message. It wouldn't have grenaded. It would have added .006 to Quench and piston to valve and lowered compression. But sence I'm at 11.1 with a .036 it would have Possibly been fine with the .o51 Gasket he Measured by. But the Quench would have been. 046-047
Thanks for the comments guys. i know it is frustrating. If you have no ability to measure, inspect or verify work, you are vulnerable.
i do inspect and measure everything my MS (Atchison Machine in London Canada) does for me, but I have to say that their work is very precise and the quality is impeccable.AG
@@goldsgarage8236 Your welcome. But the flustrating part for me. Is not because I don't have a way to Measure. It's that the measurements are not right, it's that I grew up believing that a man says what he means And means what he says and stands behind his work. I should have been Amish. But Wearing the same thing every day and the same thing as every other guy and not having a mustache with my beard would be just too much. Lol
Just go with direct injection for the ultimate detonation experience!!
Talk away. Hope knee is doing well
Thanks Ben, I am healing nicely, back to work soon. More to come. AG
Standard "deck height" of a SBC is 9.000", not 9.025"
Half of the stroke 3.480" = 1.740"
1.740" + 5.700" rod = 7.440"
7.440" + 1.560" compression height = 9.000"
Factory blocks came with .025" to .030" of "meat" on the deck surface by design. It was to allow for future serviceability. They didn't know it was going to become the staple of production V8 engines throughout the world. They just knew at some point it was going to need to be rebuilt.
Just as I thought, a quick inet search says Allen Gold IS correct...
Deck height is what you make it, and it starts at approx 9.025" as Allen said, on a SBC, hence "standard (original) deck height". Compression height is 9.00" as you said. "Extra meat" on the other hand... well... I can't say I've heard that term before. Tomato/tomawto.
@@100amps Compression height is the distance from the center of the wrist pin bore of the piston to the top edge of the piston.
@@alleyoop1234 You need better sources.
Standard deck clearance is 0.025" to 0.030" which brings the total deck height from 9.025" to 9.030", but that's not the spec of the block.
Have you ever heard of someone "zero deck" a block? That's what they mean. Bring the surface of the deck down to 0.000" variance, ergo, within spec of 9.000".
@@Carl_Jr You are correct on that. My bad.
😂
Thanks Todd.AG
Old Small block LA mopars always had an open chamber with zero quench. They should be horrible to tune, and make no hp/tq given your reasoning. In fact, tuning some high hp turbo combinations, your "quench pad " became an issue, and a source of spark knock. It isn't simple
Thanks Kyle, sounds like a challenge for sure. AG