Thread: Max Safe RPM?
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Henry Schmidt Henry Schmidt is offline
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Join Date: Apr 2004
Location: Fallbrook, Ca. 92028
Posts: 5,942
The 3.3 turbo crank is a full counter weighted, large journal crank capable of 8000+ RPM in my opinion.
The failures at high RPM seems to be attributed to rod failure. The Pauter rod is as good as any ( I know, here comes Snowman with Carrillo, Carillo, Carillo) and better than most so I don't see a problem other than rod angularity caused by too short a rod. Excess rod angularity generally causes increased friction (heat) and premature ring wear but not crank failure. This excess rod angularity also causes some concern when we start thinking about piston dwell but also not a cause of failure just poor combustion.
When I said 72-7400 rpm my thinking was it would not fail up there. It is also my opinion that it won't make horse power up there.

Just a point of fact:
The racing version of the 70.4 (935, 962) crank looks exactly like the 3.3 ( full counter weights) but has 3.0 journals.
The race engines with 74.4 cranks ran rod journals the same size as 3.0. That why we build all racing engine that have 74.4 cranks (3.2, 3.3, 3.4, 3.5, 3.6 & 3.8) with some version of the 3.0 rod. By the way out a single crank failure.
Henry Schmidt
Ph: 760-728-3062
Old 11-08-2005, 04:12 PM
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