Why are these #'s critical for a good torque build?
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- Опубликовано: 5 сен 2022
- In this, episode 71, DV and crew chief Mervin Bonnet, reveal certain easily attainable combinations of parts can generate a stronger torques curve than others. This increased torque potential can amount to a sizable increase in lbs-ft per cube so it has the same effect as making your engine feel much bigger than it really is. Since all the moves described come about through increased efficiency you can expect greater fuel mileage as a plus.
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I learn so much from all the pros and you are a real pro. I like No Bullshit.
You helped my late friend Terry Towns back in the late 80's or early 90's with his 355 sbc. He had a 69 camaro running 9.90's on the motor with 10" slicks and slapper bars. After you milled .150 off the pistons, a "good" valve job, and I believe you degreed the cam it ran 9.60's!!!
Amazing!
Richard I am planning a video on Terry's car. Any photo's? Sorry he has passed away. Good guy for sure.
@@DavidVizard I'll have to look through my photos. Phil Smith is who helped Terry with the chassis, like using Mazda 323 struts for the front suspension. Unfortunately I dont have any of his contact information. Brian Desermo, (I probably misspelled his last name) was real close to Terry and probably has some useful pictures and possible video of the car. Again I dont have any contact info. I'll look into getting you more information. Thank you for all your help past and present!
Sincerely
Richard Bentley
Richard Bentley
Thank you for passing on your knowledge! Absolutely wonderful, Godspeed.
Top notch info/experience as all ways. Thanks.
Thank you for sharing your knowledge. I hope some youngsters can learn from you. 😊
i am so glad i found your youtube videos,i will watch every one and like too, because im trying to get all i can out of my combo.thank you David
Thankyou for sharing that mr vizard.your knowledge and experience with engine's is immeasurable.peace
Thanks again David!! Loved Mervin’s spiral lock tip! The strike and compression talk was excellent!! It gave me a batter understanding of how torque is produced
Thanks for your info David! after I get this 350 together; I plan on building a 383 and trying to get comparable performance using your porting techniques with vortec heads. Your information is worth so much and at 26 years old I’m happy to listen to your wisdom so I can pass it on… well only after winning some races haha
I picked up on 1-2° tighter LSA when building a stroker, but no other event numbers (like intake closing, overlap at 0.050” tappet lift, or others). What about a general change in intake flow to accommodate the stroker cubic inches? 542 lb-ft from a 396 computes to 1.37 lb-ft/cu in, a good number. The really strong engines (maybe more race oriented with power coming at a higher rpm point) seem to make or exceed 1.4 lb-ft/cu in. I’ve seen very few that make very much more than that, but bigger torque numbers seem to favor the higher rpm builds. The fascinating thing is that the stroker motor makes 5-ish percent better torque-due apparently to bore/stroke ratio and improved combustion dynamics. Really interesting video, thanks DV!
Turbos make all that so much better though. I am at 3lb-ft/cid on my daily driver and I regularly build engines in the 5-6lb-ft/cid range for competition they are diesel though too.
Thanks for everything David.. I think you and Tony have me more than convinced to build a 383!
Great knowledge from you and your friend thank you!
Thank you David.
Great video!
THANK YOU DAVID
I've been building engines since the early 80s, had pretty good running motors. My point is I always learn something useful from your videos! Thank you and keep making them, I will keep watching!
this channel is dead for now, find his other channel called David Vizard.
great vid! also really enjoying one of your books
looking forward to a mopar 408 LA stroker combo.I plan on building one this winter for my street CUDA. will be using trick flow 190 cc / 60 cc chamber and - 20 cc dished pistons for approx. 10.0-1 compression .need to pick a cam that will work with power brakes .changing the ring and pinion from 4.30 to 3.73 .providing i can get parts.
On a 408 with 10:1up and aluminum heads power brakes = a comp XR282HR with 110 or112 Lsa should do it.
David vizard the engine wizard! Thank you for your wisdom!
Hi David, I wondered the torque increase myself and came to a potential answer.
A longer rod slows how the displacement grows from TDC through to 90 degrees of crank rotation when compared to a standard "short" rod. Since the longer rod has a smaller space through the first 90 degrees of rotation (and a bit over) then even if peak cylinder pressures were the same, the rate of pressure decay would be less. This would yield greater pressure by virtue of the smaller volume. This pressure would be applied through the power stroke until either the volume matches the short rod or the exhaust valve is open, all of which would lead to an increase in torque.
Im sure there is more to it than just that, like the extra dwell at TDC of a longer rod to help build more pressure from the burning charge.
Just something I thought was worth contributing.
and now you know why chrysler engines (especially big blocks) smoke the others on torque when most other things are equal.
Heavy Mopars are slow car's. GM #1 .
Awesome tips thanks
I clicked the notification for this and it never came through😒. I'm glad that this information is universal. Thank you for all you do.🤗
The only notifications that I have ever gotten is to go to the subscription list and check the videos.
@@hotrodray6802 I have them checked. But never get them until afterwards😒.
Anybody that worked for this man should pay him.
That's some impressive output for a "small block" alright. I am puzzled with the torque gains that exceed the displacement, that is interesting to ponder.
Thanks!
thank you for sharing with the people who need it the most great video as always sir david ,yes.they should knight you like mc cartney
What, if anything would need to be changed with this combo when using alky? By the way; you're one of the most knowledgeable individuals on the subject and also one of the few that I trust!
Mike
Your video was fascinating as always. I sure which you could do one to explain how you get away with high compression on low octane. The video you did on the 705hp, 421 sbc on 87 octane is amazing.
Cameron - I hate to say this but it should be on 107 not 110.Kiss 25 hp and 25 lbs-ft goodbye matey - sorry!
The cam grind is basically the only difference. The cam will close the intake valve later on a high compression, low octane motor. Giving it less stroke to actually compress anything. That lowers the dynamic compression, which is basically the cylinder pressure before it fires. Most NA street engines operate at a dynamic compression ratio to 8 to 9:1, regardless of what the static compression is. The higher the static compression the less stroke you can actually use to compress it, simple as that. Motorcycles use this a lot... Variable valve timing can take way more advantage of it as well....
Excellent information, takes the guesswork and huge expense out, if installing wrong parts
DV, Would you say the total friction (not just the negative impact of the side loading in the bore)of the engine; the valvetrain/ bearings etc., is the secondary player that compliments the strokers combustion and compression advantage for tq per cube? My informal experience of observing years of Engine Masters competitions, appear to favor tq production of engines approaching or at 400 cubic inches. Additionally, having guest speakers from your career is great. Thank you Mr. Mervyn Bonnet for your time! v/r wh
The GM GenV Small Block L8T Direct Injection 6.6L/401cu follows your talking points, from the factory.
9.240" Deck, 4.065" Bore x 3.860" Stroke with an 10.8:1 Compression Ratio using 0.051" Head Gaskets.
Factory 6.098" Rods give a 1.580:1 Rod/Stroke Ratio, with a 1.053:1 Bore/Stroke Ratio.
87 Octane friendly (and recommended, even @ 10.8:1) thanks to Direct Injection.
Factory Heads (Intake) flow approx 207 CFM @.300, 260 CFM @.400, 300 CFM @.500, 320 CFM @.600.
59cc Chambered Heads. Splayed 2.126" 12.5° Intake and 1.590" 12.0° Exhaust Valves.
297cc Intake/107cc Exhaust runners. Tiny ~116LSA+ Camshaft (200°/207° @ 0.050, 0.551/0.524 @ 1.8:1 Rocker).
HP/TQ at the crankshaft (running all accessories etc.) is 401 HP @ 5,200 RPM, 464 LB-FT @ 4,000 RPM (SAE).
With a suitable camshaft (similar lift, 110-112 LSA, 235/240 @ 0.050), Intake manifold w/100+mm Throttle Body
and timing/Tuning for better fuel, this stock engine can easily see 150+ Gains in HP/TQ.
Hope you can explain what you said in 8:38 in more detail, looking to learn a lot from you. Thanks!!!
And you just f....d the Spiro locks mate. I agree on the ring installation though. My RUclips on the mod for the old school expandable ring compressor.
Every big name builder I've ever seen does that.
Yeah - that didn't look right ! if so, they would ship them "pre-stretched" There was this old guy helped me with a Gold-Wing and grabbed a carb spring and stretched the shit out of it, saying "better fuel economy" !!
I would be curious as to what the dynamic compression ratio was on the 396 that you built that made 542 ft. lb. and 585hp with the 10.8 to 1 static compression.
and what heads.....?
Looking to build a 383. This is what I have. 1 pice rear main block (880) 4 bolt main. Scat 383 crank, 5.7 rods ,Speed Pro H860CP30 383 Flat Top Pistons . A set of heads World S/R I 052. Performer rpm airgap intake. All I need is a hydraulic roller cam and lifters for this block. Everything I have listed I have lying around in my shop, so all I am going to pay for is machine work for the block. My goal here is to build a 383 that is all torque for a wood hauling truck plus tow hall like a trailer for camping. I guess what I’m asking is for a cam recommendation and if these heads will work with this combination. Thanks again for your time great informational video.
Very informative video. I was just inquiring if the same concept would work on LS style engines (4.8L, 5.3L, 6.0L) as it does on small block 350 Chevrolet? What about forced induction use (turbocharged/supercharged)?
Dave I’m into early vw air cooled engines and would you think that 10.5 compression applies ,as the general thinking is 8 to 1 ,saying to keep heat down and so it doesn’t knock . Thank you I enjoy your videos and have one of your books too😊
S54B32 has very long stroke and short rod, revs to 8000 rpm and has one of the highest torque per qube, from factory.
I got a 10.98/1 (9.0/1 dynamic compression) 93 octane on street 406 (1974 817 cast) with 220 Flotek CNC .200 raised runner heads that flowbenched at 315cfm @ .600 and a cam I'm not sure abt. Older 830cfm BG HP950 It's a Schnieder 292 hydraulic roller with .622 ex/.613int 70° overlap but only 242/238 @ .050 on a 110 lsa degreed to 108. Howards race lifters, It's all forged weisco flattops scat 6" rods with 9000 series scat crank... I did a 7.13 @ 98.8 mph spinning on street tires. But feel like she needs more cam. Th400 with Hipsters brake, 4500 8" Freakshow nitrous stall but won't spray her till I get her to hook with some qa1 shocks and stickies... Thoughts on the cam?? Ty.
subscribed
Dome pistons restrict flame travel.
That's why 5.3 ls' run so hard for their size.
I actually lost sound with Mervin came on then when it went back to David I had sound?
I would love to see the reasoning behind domed piston vs dished piston for a given compression ratio.
I can't speak for Mr. Vizard, but I believe the common idea is that the "large dome" style pistons incumber the flame front [not very efficient for complete combustion] as it travels across the piston top. A flat top piston [very efficient] is ideal for flame travel, a dished piston is second best. Sometimes there is no option, and the only way to achieve the desired compression ratio is with a domed piston, like in the case of most Big Block Chevy's.
Could also be the proportion of surface area on the piston. More area on the piston can capture more of the force from the expanding gases.
It's flame front disruption
@@purestress2597 No - if that were true they would spiral-groove every flat-top piston for more of this "surface area"
No. The cost to machine or cast that increases manufacturing difficulties and cost. Ford knew 2 more cams would open up the modular engine to make 150 to 200 more hp. Money killed it.
This gentleman should just change his name too “dave thee wizard.”
Do you have a book or books and we're can I get them sir thank you
Mr. Vizard, It appears the 400 cu. in. small block is the red headed stepchild in builds. I don't understand why , people are so willing to give up cubic inches of the 400 to grind and machine the 350 block to gain 30 more cubic inches. What are your thoughts on this.
400 has really short rods, supposedly doesn't like to rev, they also didn't make a whole lot of them. Personally the way I figure it if you're looking for max power/$ you build a 454 if throwing tons of parts and work at a 350 is required to meet goals and you can fit the larger engine.
When referring to cranking cylinder pressure, and when targeting close to 200 psi cranking pressure. Is that gauge pressure or absolute pressure? 185 gpsi / 200 absolute psi?
This channel is dead for now, find his other channel here: www.youtube.com/@DavidVizard
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A good racing trick is to leave the first piston ring off the motor to make the reciprocating assembly liter and keep the top ring from locking up the motor if the ring gap is too big.
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Like always good job. Still. How do you get a cam for your motor figured out? I must be brain dead or something cause I got 2 of your books and I have been watching these videos and I don’t know how to get a cam I want. Sorry to bother you about this stuff. You said it on here to watch this that a 350 cam doesn’t work in a 396. I have the same problem I have a 318 and want to make a 396 or 400 . Big deal trying to find out how to get a cam for this. For some reason I am missing the point on how to figure this out. I got to look in your books again. I love your stuff.
Richard, your question:- How do you get a cam for your motor figured out. Coming soon - cam charts for SB Chevy, Ford & Chrysler.
@@marvingvx1 Hi there david, really looking forward to this, as I'll be building a 383 sbc soon... Your knowledge & time is greatly appreciated by us all... cheers from Australia...
Will I get better sound if I torque my timing chain to a 71 ratio
This channel is dead for now, find his other channel here: www.youtube.com/@DavidVizard
Can the LSA be tightened up on an existing cam?
Only if it is reground.
@@marvingvx1 thank you Mr Vizard.
what about a 4.155 bore (400 block) with 3.5 stroke?
Mr. G
I have done a 3.75 stroke 4.03 bore Vs a 3.48 stroke with a 4.185 bore. Both work out to 383 so it's a question of short stroke Vs long - both with the same cubes. I will dig out the results so keep watching!
@@marvingvx1 Thanks very much. By the way, I am planning on running 6.150 rods.
@@marvingvx1 I would also like to see the performance difference between 3.48 and 3.75 383sbc.both w 5.7 rod.would cam spec on 3.48 be similar to 350? have you published test results in mag or book? I have a 400 block ,350 crank,camel hump heads.new72lt1 hydcam(yeah, I know there are better cam choices, but is for street driving and don't want stiff springs and reduced reliability plus cam is paid for long ago.)I have not compared build cost yet, just thought about putting some old parts to good ?use.im in research mode and always trust your information.
Building a 408 Ford for street. 3000 pd. Daytona Coupe. Want a wide, flat torque curve. Not concerned about mega HP numbers. Any recommendations on lobe centerline....Thanks for all you do and God bless👍
@@zAvAvAz 👍
@@zAvAvAz and then the chain "stretches"
He said the 408 will be for the STREET. 106° LSA is going to have too much overlap and a loss of vacuum at idle (overly rough idle).
A custom grind based on the sum of your components is best, but for an off the shelf grind, an XE274HR or XE282HR Comp are pretty safe for 408w "streetability" and daily use.
@@richdouche8253 Thanks for your recommendations. Was perusing Comps catalog and thought the same.
@@suntzu5836 There is a channel called "myvintageiron7512" and he has a 3 or 4 part video set called "how to properly select a camshaft".
He does a really good job of explaining cam timing, and the various factors involved with that... If you have the time those videos will teach you quite a bit you never knew about camshaft selection.
If you don't have the time and just want a recommendation for an off the shelf... The two Comps are two pretty universally used stroker SBF cams that people like....
What heads and intake are you going to run on your combo?
My friend and he's son built a tug a truck that was well thought out from bumper to bumper it was a 383. Pulled alot of diesel trucks backwards on asphalt. People would say that's a pretty mean BIG BLOCK CHEVY and he said what? It's a SMALL BLOCK CHEVY! LOL
david ive always wondered if you ever blown up any engines
Witnesszero sir, Sure have very spectacularly . And that is a great subject a video!
A 496 stroker project isn't much more then a 383. And has more potential for future upgrades.
Bloodviking
The reason the huge gain in torque of a 383 is because you are not only increasing the volume of the charge, but also the piston has more leverage on the crank, being that the journals are farther away from the crank centerline.
Why is it modern motors have small CC heads, small domes. Old big blocks and small block chevys had small CC heads and small dome pistons. Yet. The old combos were called dirty heads that shrouded the valves and limited HP. So the most common and powerful BBC & SBC motors use large CC heads and huge domes. But DV says that costs HP. 🤷♂️🤷♂️ Guess my 1966 396 BBC with 98 CC heads, 10.25 comp. ratio is not antiquated junk??
DV's contention is that most combinations could be improved.
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A 350 will put out 30 more hp with a stroker 383 crank.
I am putting a Comp Cams 305H cam into my 383 stroker bored 30 over, and I would love to hear what you think of this grind?
Specifications:
Engine Make/Size
Chevy Small Block (262-400)
RPM Range
3500-7000
Lifter Type
Hydraulic Flat Tappet
Int. Duration Advertised (Deg)
305
Exh. Duration @ .050 in. (Deg)
253
Exh. Duration Advertised (Deg)
305
Int. Duration @ .050 in. (Deg)
253
Usage
Street/Strip
Quantity
Sold individually
Lobe Separation (Deg)
110
Exhaust Valve Lift with Factory Rocker Arm Ratio (
0.525
Intake Valve Lift with Factory Rocker Arm Ratio (i
0.525
Valve Lift with Factory Rocker Arm Ratio
0.525 int./0.525 exh.
Advertised Duration
305 int./305 exh.
Computer-Controlled Compatible
No
Valve Springs Required
Yes
Cam Style
Hydraulic flat tappet
Exhaust Duration at 050 inch Lift
253
Intake Duration at 050 inch Lift
253
Duration at 050 inch Lift
253 int./253 exh.
Advertised Intake Duration
305
Advertised Exhaust Duration
305
Basic Operating RPM Range
3,000-7,000
Grind Number
CS 305H-10
Exhaust Valve Lift
0.525 in (13.335 mm)
Intake Valve Lift
0.525 in (13.335 mm)
David always says tighter lobe separation is better.....after watching tons of his great videos. 106 to 107 LSA
Better off starting with a 496
Too much low end torque will break the tires free at low rpms.
A 400 will put out about 40 hp from a 350
This idea of choosing the perfect cam isn't realistic as many of us can't afford to buy and test 5 cams to find the best one.
First off , build a wedge motor and eliminate the bad geometry and block design problem . Now , why dont we talk about chrysler ? Well thats because everyone has been spoon fed chevy chevy chevy !
I think you are missing the obvious... on a 3.50" stroke, you are essentially twisting on thar crank with a 1.75" wrench. With a 4.00" stroke, you are twisting with a 2.00" wrench. Enough said.... you get it..
I would really like to contact you, can you provide an email?