this is my question. Will the new gm block work best with a 4.155 or 4.185 and a 4.250 crank or a 4.100. The motor wont see more than 7400rpm. What is the best combo for a 300shot and something that will last a while with the most power. Only people with brains answer please. thank you

 

lol! you are probably right. this thing is so long I don't want to re-read it and my aging memory is failing me. oh well i started out with nothing and still have most of it left.

 

lol well that rules me out I only have one.

 

I was only talking in terms of what stroking an engine does. Looks like I jumped in on this thread a little late.

 

Diesels also make more torque because of the burn rate of the fuel used(diesel fuel). Diesel fuel burns for a longer period of time(crankshaft degrees), which in turn makes more torque. Most modern diesels also use turbochargers, so using diesels as a example is clearly trying to compare apples to oranges.

 

no problem man it is always fun

 

What can ya say to add to this?
1st: I dont place too much value in hot rod magazine articles. BUT the one referenced here where they compared similar engines for the purpose of solving this question, is one of the most scientific I've seen them do.
2nd: When talking about an internal combustion engine, the process of producing torque isnt as simple as leverage. It has more to do with the surface area of the piston; i.e. bore size. If the piston moves just 1 inch down the cyl on the intake stroke, the larger the bore the more VOLUME is displaced. Trying to optimize this gets into complicated camshaft timing.
3rd: When its fired, the larger the bore the more ENERGY is exerted on the piston crown. Because we're talking about gas engines, it is important to consider the short duration of of the combustion process, due to using gasoline. Because of the short duration, any benefit of longer stroke, continuing to exert leverage during the power stroke, is lost.
4th: I am a professional. I have 20 years exp. I have been paying attention to the best engine builders since the mid 80s. Bernstein experimented with a small bore long stroke TF motor way back when. Not anymore.
PS engines have been short stroke, big bore for a long time. Admittedly, thats due to optimizing cyl head design.
5th; I read several times (in this thread) about how longer stroke reduces RPM. Another misconception. Just because you have a longer stroke doesnt mean you are unable to rev an engine less. In most of the applications we're talking about, valve train has more to do with RPMs than anything.
I'll turn any of the strokers we build, ls1 or lt1, as high if not higher than a stock lower end. We've built several 383s that turn in excess of 8000 rpms. Long stroke BBCs that turn over 7000 rpms.
Anyone that hasnt read that article that has posted here needs to go and read it. Its more than just your average hotrod mag engine build.

 

not really sure who you are arguing with but i don't remember anyone saying a stroker reduces rpm. also vave train is a limit to how much rpm you can turn is true if it is not upgraded. i hope how ever you are not claiming that a longer stroke motor has just as high an rpm potential as a shorter stroke motor. i am sure if you have been around you have seen plenty of destroked motors like a 455 cut down to a 440 etc...

 

Edcmat's post is pretty solid. I don't think he was arguing as much as he was
affirming the facts.

As for long strokes and RPM, I don't think too many people will argue that
Top Fuel motors are an exception? They can spin to 8500 RPM with 4.5" strokes.

I don't think the stroke is as much of the limiting issue as the weight and
strength of the rods, piston, and pin.

 

true top fuel is limited by rotating mass and not valve train. if they were not limited by rotating mass they would spin higher like an f1 car at 18,000 rpm, or a motorcycle at 13,000 etc......

 

I don't know about going that high. I've also read that nitromethane doesn't combust
well at revolutions over 9000 per minute.

If I'm not mistaken, NHRA/IHRA imposes a rev limit of 8500 RPM in the TF class?

 

Where would you get the impression he was saying that?

Here is what he said:

Emphasis mine.

Just because people do it, doesn't necessarily mean it is smart...

 

first part look at part 5, not sure what he meant.

second part read below




Thanks for your point of view i'll let them know they wasted their time and money and should give the winnings and trophys back because some internet guru said it was a dumb thing to do. And this internet guy know this based on?? I don't know you never told me. But keep the comments coming I like them they remind me of myself when I was young and stupid.

 

I quoted part 5. It's crystal clear what he meant. The valvetrain is the limit in most applications and stroke doesn't get a chance to enter into it.

I don't know who pissed in your coffee today, but I only said that "Just because people do it, doesn't necessarily mean it is smart..." What I had in mind was the fact that people would de-stroke to run in cubes-limited competitions (smart, sometimes) and other people would copy-cat them and de-stroke their street engines thinking it was a good idea because "the race guys do it." (really stupid)

Surely you agree with that?

 

When it comes to reciprocating MASS, RPM capability is based more on weight than length of stroke. F1 motors dont turn 19K RPMs just because they are short stroke, they use some of the most hi tech materials to reduce WEIGHT. Same with motorcycle engines, very light weight recip mass. As far as TF motors, the rev limiters are over 9 grand. PS motors turn over 9 grand. IHRA PS motors, the biggest motors out there (814 cubes, 5 inch strokes) turn over 8 grand. AND, all the engine builders that build these very large engines will tell you, the limiting factor in these motors abilities to turn higher RPMs is the valve train components. First the weight of the components, next the control of the valve events. The increases in HP levels and RPM in NASCAR are due to the same technology. Reduced recip weight and improved valvetrain components. NASCAR actually imposed limits on what type of materials could be used for internal engine components.Their motors still have the same stroke, roughly 3.5 in, that they've always had.
With the exception of class racing, you rarely here of anyone destroking an engine. Most people stroke because of the benefit of added cubes.
PS Before you go calling someone young and stupid, you ought to at least find out who you're talking to, or about. I am 40 yrs old, have 20+ years as a professional tech and business owner, and I build hi perf motors everyday.
SBCs, BBCs, LS1s, LT1s, chryslers, fords, supercharged, turbocharged, etc...
This aint no "I seen it on HOTRODTV"
Back to the original subject, torque is influenced less by stroke length than the increase in cubes. And when it comes down to it, torque is more likely to be increased from an increase in BORE size due to the increase in piston surface area that the cylinder pressure exerts its force on.

 

Any of those cranks should turn 7400 RPM. But its going to depend entirely on the valvetrain if the motor will spin that hi, and if it will make power at that level.
In ANY application, street, strip, etc, its beneficial to maximize the efficiency of the heads. So, the bigger the bore, the better the heads breathe, the more power making POTENTIAL they have. (3.9 bore for LS1s, or 4.0 bore for LS2s?)
If all the cranks cost the same, I would obviously use the longest one, not because it makes more torque, but because it makes the engine BIGGER. If you were limited to CID, I would use the biggest bore, and then figure out the stroke to make the CID what I want.
Not sayin I gots a brain, but I do gots speariance....

 

Other than maybe fuel economy, how many of you would actually take your
383 (382), or 427 and reduce the stroke?

Do you think the car would be any faster, or more powerful at higher RPM?

(Let's assume the before and after supporting mods are proportional when
reducing the stroke length.)

I bet those in the gray area are thinking twice now.

 

No doubt 99% of people would still want the cubes. I think the only time it is an issue is if you are in a class that has a weight penalty for displacement or a displacement rule in general. Also for the OE's when they want to hit a target mpg and keep the cubes down.
There will always be pluses and minuses either way, and with a stroker it is usually cost. It is cheaper to just hone your stock block and buy a crank in most cases than it is to build a new larger bore block with a new crank. Also with Gen III's stroking was the only game in town for a while, and it is good for street races who want to claim stock cubes/stock motor.
Me personally I am going to build the largest displacement motor I can afford, if that means I only have enough for machine work and a new stroker crank then that is what it will be. If I can afford a new TSP LS2 402, then that is what it will be(or a l92 454+)

 

lol very good. and your right the coffe was bad today. and of course i agree with you because you agree with me. people destroke motors instead of taking a smaller displacement motor and stroking it. why? because they want to win. and you win with RPM. again thanks and please don't take the comment i made personaly at one time i was young lol and i could not resist the jest. but to be serious for a second; displacement wins and bore wins over stroke. there are problem with large bores and high compression getting the right flame propagation after a point and then you ad stroke or more cylinders.