Thoughts on MAX rpm on Big Cube Engines

[ProMod83]

NHRA has the rear gear set to a 4.56 for a turbo promod. Looks like most guys will be better of building something around 526 like it's blown counter parts as at 650 cubes can you really turn enough rpm with out hurting parts.

Most guys say 8500 for a 600 inch motor. Just wondering what everyone thinks on the issue. I know bore and stroke play a major role.

Lets get some discussion going!

[TSTOM]

Bore and stroke come in second to air speed in the intake port and valve train stability where max rpm is concerned
I here of 800" PS engines turning over 8000....now that's some piston speed!

[TOL]

Originally Posted by ProMod83

NHRA has the rear gear set to a 4.56 for a turbo promod. Looks like most guys will be better of building something around 526 like it's blown counter parts as at 650 cubes can you really turn enough rpm with out hurting parts.

Most guys say 8500 for a 600 inch motor. Just wondering what everyone thinks on the issue. I know bore and stroke play a major role.

Lets get some discussion going!

Is this a new rule meaning that turbos can't run numerically less than 4.56? How many gears are they allowing? 3-disc clutch?.......

[Little Pierce]

IHRA Pro Stock motors run up close to 8500 rpms and they are 800 inchers

[ProMod83]

To be honest i didn't know the turbo cars had a rule on rear gear, i called AMS today and they said you can;t run less then a 4.56.

I was going to build a 600 in motor with some sonnys chemi heads but sonny thinks 8500 will be the limit.

I need to go at least 9000 with a 4.56 to be in the ball park. What do the blown alky 526 guys turn for rpm?

[Big Blue Oval]

I asked Jimmy Rector once when they shifted and he said "when she quits pullin" lol

I have been told that the "legal" guys are twisting close to 10000 in order to run the number.

Robbie

[sean70ss]

I have seen anywhere from 9400-11,000!!!!!

Sean

[Big Blue Oval]

Kinda jumping around here, but I would like to know everyone's opinion on the Brad motors vs the AJ's. I have heard that the Brad's have more valve train problems.

Nick, if this draws a lot of discussion, please move it as I don't want to mess up this thread. The talk about RPMs got me on this.

Robbie

[ProMod83]

I really thought the limiting factor would be air flow, I mean Sonny says he has some customers running 10k with the heads so the geometry is there.

If 800 inch guys are goin 8000-8500 i don't see whay we can;t go 9000-9500. Esp with a square or under square motor.

[johan]

AMS rules : Supercharged Entries: 4.56-to-1 rear end ratio (final drive) maximum.
Turbo cars are subject to all general rules for Supercharged cars.

4.56 maximum final drive, but from witch direction ?

Is it from 0-4.56 or from 4.56-100 ? ? ? ? ?

[ProMod83]

I'd imagine that they are trying to limit the mph on these cars. So i would guess 4.56 is the lowest numerical number.

[srcracing]

We Run With A 526 Hemi Normally 9,500 On Kill 10,500 With No Problem At All. I Guess It's The Way It's The Way Oddy Builds The Engines