MILD THUNDER

iTrader: (3)

Many guys spin their engines over 6000rpm with both standard and long stroke engines. As far as torque goes, I can tell you this.

My friend Joe's 522ci 4 inch stroke 4.560 bore setups, with a 1071 blower , made more torque everywhere thru the rpm band, than my other buddies 540s that are 4.25 stroke. They had different cylinder heads and what not, but that short stroke setup simply made excellent torque. Around 930ft lbs if I recall.

Mike tkach also recently did a 509 with a whipple and gm iron heads that exceeded 800ftlbs from 3000rpm up. I've seen plenty of guys longer stroke engines not make that power.

Bottom line, there's alot more to the story than just the stroke. Its the overall combination of parts. As stated if you can do large bore large stroke, than that's a no brainer. But if you are at a crossroads of whether to invest a few grand into a stroker crank kit for your 502 or 454 , and you only had budget for that, I'd invest the money into the top end of the engines and keep the 4 inch stroke. A properly setup high flowing 502 will beat up on a poorly setup 540, as will a 454-468 beat up on a poorly setup 489/496. Just my opinion .

hogie roll

I would "rpm" either one as much as the cam and valvetrain allows.

Like I said, it's been tested, and with the everything else equal, there is no significant difference.

vintage chromoly

iTrader: (3)

When we took apart the supercat engine we were surprised with the 3.920 crank and a 4.540 bore. Class rules dictated 509CI and we expected a 4 inch crank and a 4.500 bore.
My buddy called up to baker who did the heads for the engines and the guy he got on the phone said they found that the optimum bore diameter for the spec heads was 4.540 so they worked backward from there to come up with the stroke.

As has already been said, it has a lot to do with unshrouding the valve and maximizing the combustion chamber.

rmbuilder

That also hold true for a forced induction engine and a naturally aspirated counterpart. The optimal port cross section area, volume, and velocity profile for will be the same for both, all else equal.

Bob

CDShack

Clearly my answer was kinda simplistic for a rather simplistic question, the basics being at sweep near 90* per cylinder, you gain a slight advantage on low end torque, much like a longer wrench turning a stuck bolt. Torque (the only thing measured by a dyno) is also, in part a result of cylinder PSI x surface, so you are correct, that can't be discounted. In real life, my experience has been the advantage of larger bore force closely offsets the advantage of stoke, so that both motors OP describes at 5500 rpm (all things being equal) will be hard to tell apart.

SB, you know I'm old school, so if I'm getting to choose a motor for a boat, I'd take long stroke in a big ol' lumbering boat every time. LOL!

BajaIceBreaker

I like all the insight. Very entertaining. I think there's a few takeaways from this...

1) Go with the larger bore AND the larger stroke. --> "The no-brainer"
2) Bolt on a blower for more power --> Not really part of the qusstion, and completely complicates the question, but 100% agreed
3) The consensus seems to agree, all things other things considered equal --> No measurable difference

With that in mind... let's throw in a few more variables...
--Now i'm starting to get real to life--
1) Let's consider it's a retrofit hyd roller cam at about 589, 610 lift
2) Aluminum Dart Pro 1 at 310 cc
3) 800 cfm Holly vacuum secondary
4) No room for a blower (blowers are out of the question)
5) OK exhaust (aluminum manifolds with individual runners for only 12 inches)
6) Purpose is to go 60 MPH and drink heavily when I get there in a 13,000# Baja
7) The 4.25 stroke engine is around $3500 the 4.00 stroke engine is around $4000 new (same warranty)

Oh... one more variable.... I'm not going to build them bigger in the future.

GO!!!!

SB

iTrader: (1)

That $$$ For shortblocks new ? And what parts are in them?

dereknkathy

Stroke is cheaper to add later than bore. Crank and pistons instead of block and pistons. Way back in the old days they didnt neasure displacement. They measured bore area. Felt it made little to no diff how far the piston went up and down.

GPM

Diesel

Full Force

iTrader: (5)

You are not getting anything good for that kinda money in shortblocks.....and why run vacuum secondary? a place to fail at WOT