Those Damn Small Block Chevy 400 Steam Holes Again......
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- Опубликовано: 27 дек 2023
- There seems to be some misunderstanding in the comments, about the correct size and angle that the steams holes in 400 sbc heads are drilled at. WHY? IT IS WHAT IT IS.
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I drilled mine 1/8 inch never had an issue, even in 90s temp outside. Love my small block 406.
Same here
I`ve built dozens and dozens of SBC 400`s in all sorts of applications and only put those holes in for street use. I`ve found that if your engine is running generally over 2500rpm ya don`t need them. The last 4.155 bore SBC I did a year ago was a dart siamesed brand new block and it didn`t have any steam holes in it right out of the box. It runs in the street idles all over the place turns 7400rpm if asked to and is a pleasure to drive. My customer loves it. It`s a 434cid pump gas motor, he drives it to the stores all the time and then beats it like he stole it at the turkey rod runs and the spring flings here in daytona. For what it`s worth.. He even took it on a scavenger hunt all over half of Volusia county...no overheating in the middle of summer in Florida...92 degrees
Aftermarket performance blocks and Bow Tie performance blocks have reinforced thicker decks that eliminate the need for the steam holes. Thanks for the feedback👍.
I'm not an 400 expert. I never noticed the difference in the steam hole sizes or angles. I'll be looking tomorrow. Cool...
Don't feel bad. I completely built one, put it in the vehicle, and didn't realize I'd missed putting in the F-ing oil gallery plug the port-side head half overlapped in the back until I started it and oil went everywhere.
😲 Thanks for sharing.
I have always just drilled them 1/8 for all 6 never a problem.they are however 2 different sizes I have 3 400 s and all factory motors and the sizes Are 3/16 and 1/4 respectively
Ive owned 2 chevy's with the 400 cu engines ! A 76 wagon and a 77 blazer ! Never had an issue ! If you upgrade to a a modern multy layer head gasget problem solved !
THANKS for the feedback. Head gasket quality is a major factor. The 400s with the most overheating issues were the later models with light weight cast iron heads. Particularly the 882s. Have a Happy and Safe New Year!
May have been due to rust, but the holes in a stock 1970 400 I took apart were a bit bigger than 7/32, yet a bit smaller than 1/4. When I put aftermarket aluminum heads on the rebuilt motor, I used a 1/4 drill and a stock 400 head gasket as a template.
So you mean like 15/64"
Maybe, holes has rust and other crud built up. A 1/4 drill cleaned it all up.@@tomupchurch4911
I believe you need the steam holes from personal experience. I don't dwell to much on the size. Never gave that any thought as long as they are there. Over heated without steam holes ran cooler after steam holes added
Yeah, the engine doesn't carry a scale to measure it's own steam holes. They can vary in size as long as they're doing they're job. They can be a little smaller or bigger. To a point. My point in the video was They are 1/4 and 3/16 respectively from the factory. I'm making a jig with drill bushings. So, the bushings I'm using are 1/4 and 3/16. I'm going with the standard. Other people can do it differently. Thanks for the feed back and have a happy New Year.
I've run many 400's in my car without steam holes. Thousands of street miles, hundreds of passes, 7500+ RPM, idle in Los Angeles traffic, a couple Power Tours, 100+ degree weather, 200 shot of nitrous, as much as 14-1 compression...you name it-no problem. On the recent Power Tour to Las Vegas, my alternator belt took out my electric water pump wires when it came off, and on the return to the pits after a pass the Autometer temp gauge was pegged (maybe 300°?) No problem. Regular old Felpro 1004 gaskets, never even blown one.
All you need is enough to bleed air out so the deck isn't air locked. It will help to have a 1/4 inch hole at the exhaust side to allow more water to pass through.
The exhaust side is the hottest part of the head. Not only does the exhaust blow out that side but the spark plug's located there, where combustion's initiated. The size of the hole doesn't have to be exactly 1/4. I just stick with it because that's the standard from the factory. It can be smaller or larger to a point. As long as it's doing it's job. One viewer said 1/16. That's stretching it a bit. Thanks for the feed back. And Happy New Year.
Ben building and runing 400 sbc since 1975 have one in my 77 gmc over 800000 miles never ben hot .just drill the dang holes clean up casting flash run good gaskets you wont have any heating truble..
Recirculation during warmup while the thermostat is closed is important, too. There isn't enough emphasis on cooling system function on RUclips, IMO.
Thank you for bringing that up. That is a good point to be brought up in the future. I want to move on from this steam hole thing. If these blocks have poor circulation, cheap poorly made water pumps, poor maintenance, etc. All the steam hole talk in the world won't help it. Plus, in the late seventies Chevy made some light weight head castings that overheated and cracked which led to the 400s reputation for being an overheater. There's plenty of info out there on which heads to avoid though. That would be to redundant for a video kinda like this hole thing 😆. Have a Happy and safe New Year.
@@silverstreak232 I always figured I'd probably never run a 400 but the princibles apply across the board.
Have you ever seen the water pump recirq hole plugged off, not sure what they had in mind and nobody ever mentions it.
Makes sense. Steam wants to expand, plus the exhaust side of those old blocks was the biggest trap.
Injoy the motor you built. It will stay cool..
Quarter inch drill bits don't break as easy
Easy fix, just run a Stewart water pump, No need for the steam hole at all. Because the pump will make 31 lbs of water pressure in the block.
That's great could you share more of your experience with 400s and using Stewart water pumps. There's seems to be a lot of interest in this topic lately. That's why I named the video Those damn........... To me it is what it is. Anyway, not all cylinder head water jackets are created equal and if you could share some of your experience with this issue it would be great. By the way, I'm not monetized or receiving any payments for doing this. So, what I say is sincere and from my own conscience. Thanks for the feedback.
I've built and am building sb400s.... For years now.... Edelbrock has ther own warranty guidelines on using their heads on a 400 wen drilling... I noticed in ma years that earlier 4 bolt blocks r shit...
Steam holes always hav cracks.... Ther thin n the crank webbing and prone to crack w studs. Best to use longer rods,
N always overcool w big radiator...
Never went over .030 wen building...
Building a low compression turbo mover rite now.... Only thang stock is da block.
chevy racing says if you don't operate under 3000 RPMs you don't need the steam holes.
Thanks for your feedback. I'm aware of that. This is going to be a street engine.
Bill Here. Are you still in ECG? I run "Mr C/gas 37 Chevy along with Denny Stewart's 48 "Outlaw" Anglia
I think you have me confused with someone else. But if Providence has me 🏁 racing in a gas class someday, I'll be sure to let you know!
IT'S A MOOT POINT , first ask yourself why is it there ?? only 1 reason ,to vent the pocket created by the Siamese cylinders , you can drill it at a 1/16 of an inch and it will do what it is suppose to do .. Remember that you could drill it bigger , but the restriction is the head gasket . as I said the size is mute , as long as it vents the cavity in the block .... if you look closely at the block the upper hole is not needed because the cavity in the block is at an angle that allows the steam to escape ... a lot of shops I know won't even drill them , I do just the lower row ...
No kidding. It's not rocket science. But, someone (a certain person in the comments of a previous video) wants to make a perpetual argument out of it, trying to say that the holes drilled from the factory can't be 1/4", when in fact they are. I agree with you. They can be what ever size, as long they work. I'll stick with what's worked for 50+ years. But to make things clear. And now I feel like it's beating a dead horse, the holes closest to the exhaust on factory heads are 1/4". I Know it's a mute point. They're 1/4". That's what they are. End of story.
@@dave8895 fixed
True, any air/steam near the upper hole can simply float up and escape via the big hole just above the upper steam hole location... allowing coolant to replace that air/steam... surprised the GM engineers didn't realize that... maybe they were going for symmetry with two holes...
Ok, here is why GM put steam holes in the 400 SBC. As you know there is no water between the cylinders. Because of that , this is a point for steam can be trapped , and air is not a very coolant. The only time this is a problem, is when you have been driving , say on the freeway for a long distance, and you pull off the freeway to get gas. Now the water pump slows down and the engine heats up. This is when you get steam trapped at the top of the block and will not come out until the engine cools off again.
So the secret is to use a Stewart water pump, which can make 31 psi of water pressure in the cooling system. This high pressure does not allow for the coolant to boil between the cylinder walls. Easy fix.
@racerd9669 Very interesting. Thanks. I'm sure others will appreciate your information. I sure do. I also understand that Edelbrock makes a high volume water pump that produces similar results. I don't know much about it other than it's quite expensive.
400 pure junk built one external ly balanced need big radiator he'll on gas pure junk 350 best
You don't need the steam holes if the engine is being run above 4,000 rpm for racing...
This is for a street engine. I have two 3rd members for my 9 inch. 3.70 and 3.00 So, it's not going to be running over 4000 rpms on the road much. Thanks. Have a Happy New Year!
Sometimes you plug the lower ones in the block and they still cool enough...
It's a never ending debate. Some folks claim to plug the holes in the block and never experience any trouble. I'm not doubting them or saying they're all lying. But, there's a lot of cases where people ignore the steam holes and have head gasket problems. When they put the steam holes in the heads, The head gasket failure issue goes away. I believe that an ounce of prevention is worth more than a pound of cure. So, I'm opting for the steam holes.
Chevrolet engineers installed steams holes for a reason, I've always drill the holes
I wonder how many out there run with no thermostat bypass? This is important and highly depends on what you're trying to accomplish, IMO. Why would someone rather run without steamholes? How many and size were worked out by gm decades ago for their intended purpose.
Bro, time to take it to Chevy and get the blue prints.
I don't know why some people have to make an issue out of a non-issue.
The reason for the steam holes is because the cylinder bores are siamesed in between the bores you have to remember the original small block Chevy was only 265 cubic inches and then they started increasing the bore size until they cylinders inside the cooling jacket are connected with no room for water flow in between them this causes uneven thermal expansion and out of round cylinder bores and the need to have steam holes this is not ideal for reliability or performance but it still a necessary evil without changing to a larger engine block if you want to obtain maximum displacement. The steam is being created because of the interconnected siamesed area is a hot spot between two cylinders that are pumping heat into where the two cylinders are connected and this area is un-cooled because there is no room for coolant to flow between the cylinder bores normal smaller displacement small block engines that have room for coolant to flow around the entire cylinder liner don't have this problem and they also maintain rounder cylinder bores better too when they are hot or cold. For reliability the ideal displacement for a small block is around 327 cubic inches or smaller with 350 being the practical maximum for a blend of performance and reliability for most factory castings the 400 small block is a stretch in the original small block design as a filler between small block and big blocks when you go to these higher displacements you are thinning out the castings so much that you might run into cracking issues especially if the castings are not perfect say with a little shift in the core that forms the cylinder wall that being said obviously the 400 engine worked or they made it work somehow it is at the limits of what is practical. I'm not counting the 383 stroked engine combo because it isn't a factory small block one when I was referring to the 350 being the max practical small block size the 383 still uses the stock 350 bore anyway besides the overbore to clean up the walls for the rebuild. I am fond of the little small 305 cu inch personally just because they are cheap to buy plentiful underrated good on gas and last a long time simply because they are under powered compared to the larger displacement small blocks but this liking is definitely not from a performance viewpoint. If you think about the steam being created in the 400 block it must re condense in the radiator tanks or else the pressure would build up and it would have to be vented out of the overflow through radiator cap it doesn't seem ideal to be making steam in the cooling system reminds me of driving around with a blown head gasket with exhaust gas in the radiator
Well prepared production 400 castings have been used in racing and street applications with success for many years. David Vizard has a production block for sale, that his shop prepped. What I have is a 511 two bolt main casting from a 73 Caprice wagon with around 80K miles with no previous rebuild. The block is "seasoned". Any cracking or core shifting would've taken place during this engines earlier life. So, I don't expect to have trouble with it. The shop that did the machine work did all the inspection needed when they assembled the short block. The block is sound for my application (street hi perf). Now, the production 400 blocks, the Chevy Bow Tie block, and aftermarket sbc blocks with 4 1/8 bores and siamesed cylinders differ in the the fact that the aftermarket blocks and BowTie blocks HAVE THICKER REINFORCED DECK SURFACES. That's how they can get away with out the need for the steam holes between the cylinders. I've had this engine since 1984 and haven't put it to any real use yet. So, nows my chance. The 400 sbc has been out of production since the end of 1980. This is the last 400 I plan on spending any time or money on. They're outdated. Thanks for your feedback and have a SAFE AND HAPPY NEW YEAR!
And you can get 331 cubic inches from a 305, and will tach to the moon.Granted you can't run a 2.02 valve on a 305. You can get a set of 1.94 aluminum. And make quite a bit of power. A little spray, or squeeze on that dude, it'll hurt a bigger engines feelings .
@@silverstreak232 Built my 427 stroker on the DART SHP. Beating on it for several years . 180-190° , hotlapping the 8th.
Yeah the after market blocks are probably thicker in the right areas but because they still use the same bore spacing the engine block is still a compromise at best aftermarket castings may have better quality control though performance engine builders back in the day bought multiple engine blocks and had them sonic tested to determine core shift and thin castings the average joe smo wont do this though so it is a bit of a crap shoot when you start to push these engines harder and harder. Core shift cannot be corrected all by itself from an an engine sitting in a junk yard that is a defect from the casting process of the engine block if it is present at all the engine block shouldn't be accepted for a performance engine build the idea behind a "seasoned" engine block is that heat cycling the block will cause any distortions to occur then this will be corrected after the first engine rebuild assuming it is performed by a competent machine shop this is what blueprinting engines is all about and this is not something you get from most machine shops even the good ones Winston Cup engine builders used to vibrate their engine blocks for 24 hours or 48 hours on a machine called a vibromax this is s substitute to what you think of as a "seasoned" block really it is a form of stress relieving the casting or the forging using ultrasonic and this must be performed before final machining some guys call it relaxing also but metal can retain tons of internal force per square inch of thickness like a bow can when it is drawn back but inside the crystalline structure of the metal itself in factory production this stress is not accounted for and this is why you have probably heard of guys taking their brand new cars and having a good machine shop rebuild their new engines after breaking them in and gaining some horsepower even though the gains are minute in racing these minute gains are everything to the average guy they mean nothing. @@silverstreak232
That's a good bit of information, condensed into five sentences. 👍
I plug them it don't matter the application. All the 400s I built have never had a heating problem, you can't buy an aftermarket head with steam holes.
So hear me out... What difference does it make? I'm not a 400 guy. I knew they had steam holes and they're rare enough where I'm at to not see them, ever. So what difference does it make as long as the gasket doesn't block them?
Thanks for asking, Sam. The holes don't have to be exactly 1/4 and 3/16. The engine doesn't know what size they are, as long as they do they're job. My point was that a person insisted that the exhaust side steam holes could't be 1/4 because of what he measured in a head gasket. I just pulled that head off the shelf to show they are in fact 1/4. That's the nominal size from the factory. And yes, 400s are getting rarer. They've been out of production for over 40 years. Have a Happy New Year.
@@silverstreak232 I guess I just don't understand what or why the argument was started. Doesn't seem like the port size or angle matter much then, right? As long as everything lines up and acts accordingly, everything would be fine, if I'm not mistaken.
They are drilled at an angle...
The 3/16 holes closest to the intake are drilled at approximately a 10 deg angle away from the head bolt hole, from the factory.
3/16" is .187.5"
yes, 3/16 = .1875
Been taking shop classes for awhile. If I answered a measurement question with .187.5 I'd have lost 2 pts on a 50 question test. Never play chess with a pigeon (That RUclips commenter). Or else, Oh you know, the thing! Lol!
What is the big deal? Is it worth the headache to prove to others what you already know.
It can be amusing sometimes
"Promo SM" 🙋
You don't need them an I drove a sb400 I had 041 heads 11 to 1 comp drove an race it every weekend it was a daliy driver
Youre playing chess with a pigeon my friend. RUclips commenters are like A-holes, everybody IS one! 😂
Sometimes, the entertainment factor is worth it. 😅
🥝✔️🤭
???
@@silverstreak232 Kiwi Appreciation, Laughing Quietly.
🥝= Kiwi
✔️ = Appreciation
🤭 = Laughing Quietly
400 heads on LT1 1971 350 block. That's exactly what we saw on disassembly. Thanks for the video. Proper, Solid, Righteous Info, Thanks.
I plug every damn steam hole I can.
They will flat screw up an aluminum head with any kind of BTUs generated in them.
I’ll take a person’s money if they insist.
I dont drive a steam powered car so I don't need steam holes LMAO don't blow up your boiler