Non Conterweight 66mm cranks

[davidppp]

Hello all.

I'd appreciuate advice on using this in racing engines.

What will be the downside?

Case pounding, or crank breakage?

Is the safe RPM limit lower..if so why?

My grinding wheel sparks tell me there is no differnce in the steel composition from counterweight cranks..

Thanks for any information..

David

[Grady Clay]

David,

From what I understand, and I may be wrong, the difference isn’t in the metal but in the process. The non-counterweighted crank is high quality cast steel. Not having the counterweights negated the requirement for forging. I have also heard it is close to the same steel formula as the forged crankshafts but I’ve never had an assay done.

To my knowledge Porsche has only used forged crankshafts in their race engines. In fact the only street engines with these cast steel crankshafts were the lower power, slower turning ’68-’71 911Ts.

That said, I know of several (and heard of many) who successfully used them in high rev (<8000 RPM) race engines. I have never heard of one braking or cause any additional distress to the “flexible flyer” magnesium crankcases. With a high rev engine and proper moon cutting and boat-tail of the case and cylinders, the non-counterweighted crankshaft significantly improves the “windage” of the crankcase.

With any mag case, I would choose to shuffle-pin the case at a rebuild – along with all the other mods learned form 30+ years of experience.

Best,
Grady

PS, you can get a moderator to move this over to the 911 Engine Rebuilding Forum and get more response.

[jstobo]

An old racer told me that he preferred the non counter weighted cranks because they would rev up faster(probably due to less weight). When you are accelerating out of a turn the faster rev the better.

[davidppp]

Thanks so much again, Grady.

I knew you would have some good data..I'll ask for this to be moved..

Kind regards
David