ci/stroke/percentage

I have had to different motors in my altered this year a 4.25 stroke 496 and a 3.75 stroke 427 w/ the same heads and cam/blower etc and much to my surprise at 30% od the 427 ran just as strong, is there a chance the 427 is that much more efficient on the ci end or is the the shorter stroke spinning up faster helping. 14-71hh retro. Also is there any truth behind the myth that the shorter stroke is easier on the crank and mains? Just trying to figure out the best combo for me the 4.25 stroke motor hasen't held up well the last few years but the spare part junk seems to work.

 

Troy call me 315 436 6653

 

Rod length / stroke diameter?
Dome height?

 

Blower limited? 30 over is 30 over and that's all ur gonna get

 

Big bore, short stroke motors are usually more efficient than long stroke motors. Long stroke cranks are brutal on main and rod bearings, not to mention the block also. Short stroke cranks have more overlap which makes them stronger also.

 

Sometimes bigger motors don't make any more power than the smaller cubic inch because the blower has to fill a bigger volume, so if the blower boost is already maxed out, the boost will be less with a bigger motor. In a lot of cases, boost is more important than cubic inches.

 

So I'm not crazy thinking that the smaller cube motor should be more efficient than the larger, I was planning on putting a shorter stroke in my good block but others have told me to go bigger to make better tork numbers? Boost # should be higher in the smaller cube motor at the same percentage over than the larger cubes? If I'm way off than please tell me? Is the stroke=tork thing true?

Thanks Troy Liebi
LIEBI RACING

 

All things being equal, the smaller motor will make more boost. You may get more torque out of the bigger motor, but you need the horsepower in the mid range and top end to run fast.

 

I've never been in a good situation to test this question but here is my thoughts.

If you take your short stroke combination and simply change the stroke and appropiate rods I believe the reason it becomes more "torqey" is because your cam and ports didn't change. My thought is that the larger motor has the potential of making more power (albeit not much more) with the appropiate cylinder head port and cam changes.

I would love to test this out but I'm about 1/2 of a million dollars short

 

Almost 30 years ago (TAD), I found the larger motor (4.0 stroke) ran stonger in 2nd gear than the stock stroke BBC. I had the same blower and OD% on both, but I think the gearing I was running at the time was the difference. I had a 4.11 rear w/ 3 speed Lenco (2.20-1.31-1), and I think the extra torque worked with the big ratio drop. The next year w/ the smaller stroke (and better engine parts) I raised the rear to 4.56 and lowered the 1st gear to 1.98. It was also my experience back then that the smaller engines fell off quicker when the blower boost declined.

 

So if that theory works (and there seems to be plenty of evidence that it does) would a Hemi style engine be better with a 4.250 hole and a 3.75 (stock stroke) arm for Nitro too, or does that yellow stuff throw all the rules out the window?
Thanks
Geoff

 

Thank you all for responding I appreciate the help and knowledge and I run on alot of slippery tracks so w/ the help I recieved and the testing I've done I think I'm going to stick w/ the short stroke that seems to be working for me for my next build.

Thanks Troy Liebi.