85vet

Interested in your thoughts on the differences between an externally balanced vs internally balanced 383 crank.

Is there a benefit in useing one over the other?

I think the internal balanced will allow me to use my current 350 harmonic balancer vs going up to a 400. This setup then would make the engine look completely stock with no apparent outside changes. :cool:

Is there any other benefit to an internal balanced crank?

jackson

Yes, by using internal you can retain 350 balancer & flywheel/flexplate & save money there. Of course if your balancer is original 1985, I'd get a new one for a stroker build.

I realize there are a FEW internal balance CAST 383 cranks ... more internal balance forged ... and a glut of external balance cast.

AND ... SOME of those bargain ($100 < $200) aftermarket 383 Cast External-balance cranks ain't such a bargain. SOME have very creative counterweight finishing (aka hacked) that results in a balancing bill $ 2-3 times $ what it should be. IMHO after balancing's factored in, a good Forged 383 Internal-balance crank may cost only $100 - $200 more in the end.

CORKVETTE1

internal ballaned job could set you back $300-$600 depending how much mallory metal they have to use :cheers:

No Go

Are the SCAT forged cranks considered internally balanced?

Speaking with the phone technician at SCAT, he wasn't being very helpful in his statement-internally balanced in front and externally balanced in the rear on their forged 1 piece LT1 cranks.

Thanks.

:)

vader86

My Lingenfelter book kinda explains what the differences are, but he doesnt really say what the advantage is with internal or external :confused:

71roadster

I am buying the scat crank for a 1 piece rear seal with a 3.75 inch stroke to build a 383. I will have the late model flywheel machined along with the rest of the rotating assembly to be internally balanced. It is a lot less stress on the crank and block as standing waves are minimzed in internal balance and maximized with external balance. Scat says there cranks designed for internal balance have extra material in the counterweights to reduce/eliminate the need for mallory metal. And if you use light weight rods and pistons you further ease the balancing process and reduce costs. I am going to use manley sportsmaster rods which are some of the lightest on the market and fit my horsepower target perfectly. They are a lot better and cleaner designed rod then the scats or the eagles and it clearly shows when handling them. Plus, they are only $100 more then most others and about 100 grams lighter. Thats a lot. Then if you use lightweight pistons you help even more. KB hyperuetectics are about 425-450 grams each compared to 500+ for most forged units unless you go with hi dollar lightweight forged. Either way, the lighter you keep the rotating and reciprocating weight, the cheaper it is to balance.

It would be easier and cheaper to just build external balance using the larger harmonic damper, but I kinda like complicating the h3ll out of everything.


cheers
Chris

85vet

Thanks, guys.

Keep it coming - this is great stuff and knowledge is HP and longetivity of your engine :cheers: .

Just curious - is the original crank on the 85 internally balanced?