Crankshaft cutting

[Shelby VNT]

I've seen alot of guys serious about the performance of their engine cut the crank. The reason is to be able to run bigger bearings, which generally is thought to improve your engine's lower end strength, correct? I've even seen a few turbo Dodge guys do this. Question is, are people still doing this modification and does it really have an advantage? For a while in the older hot rod days I thought a few guys were also trying the opposite, running a smaller bearing because that was thought to be stronger. Any input?

[gasketmaster]

Nathan,
The strength of the crankshaft is determined by the material it is made of,the radius in the fillet area and the pin overlay.

The reason for running reduced diameter crank pin sizes is to reduce bearing surface speed.This is normally a mod done for high RPM engines.

However,this also reduces pin overlay which weakens the crankshaft.

A short stroke crankshaft is stronger than a long stroke crankshaft because more of the connecting rod pin overlaps on to the main bearing pin.

A naturally aspirated SB Chevy engine will rev quicker and make more power with a light weight profiled crank only weighing 35 lbs. but that same $1000.00 crank will break in a twin turbo V8 application.

There are different cranks for different applications

[Shelby VNT]

Alright, thanks Terry. I understand what your saying. So cutting a crank on one of our turbo engines wouldn't really make a big difference would it? Besides making it lighter or possibly weakening it and maybe giving longer bearing life with slower rotating speed, is there any good reason a guy might cut a crank for our engines? I don't really see it as an advantage, unless I'm over looking it? Our 8 valve engines sure don't scream the high rpm's, specially the longer stroke 2.5 liter.

Another question. If a crank is cut 10/10, what does that mean?

[gasketmaster]

Quote:

Originally posted by Shelby VNT So cutting a crank on one of our turbo engines wouldn't really make a big difference would it? Another question. If a crank is cut 10/10, what does that mean?

No, lightened internal parts are for n/a engines.We make our power with the turbocharger.........we just need strong reliable internals


It means that it has been reground .010 under standard size on the bearing surfaces.This is normally done because the surface was out of round,tapered or blemished.

[Shelby VNT]

Thanks again Terry. Your the man! When nobody else answers my questions regarding blocks and O-ringing, your there!