SoCal Jet Boats
Tech Talk => Engine Mechanical / Electrical => Topic started by: beerjet on July 20, 2008, 11:43:24 AM
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GM steel crank . Whats the most compression and RPM can it take . I'll get a casting number off of it today .
-beerjet-
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If you go balanced, Knife edge (for windage control), Nitrided and machine properly, I'm not sure if a factory GM crank has any weak points that the high performance shafts do, the age is the only thing to keep in mind, the tensile strength will drop over time, but should be able to support 7k at 1,200-1,500 HP, the CR is pretty much irrelivent because the CR has no effect on the crank when the engine is at speed, it's, torque/speed (HP) you need to keep in mind, you can figure it out mathimatically by using the horse power formula, and a factory style, proffesionally prepped crank should be good for 800-900 ft lbs. IMO.
I've seen some nasty big blocks with OEM cranks, and have seen them hand high performance (best of everything) big blocks their ass!
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I've seen some pretty impressive stuff too , just wondering if it would be up to the task . the one I have looks like it came out of a relativly newer motor (90's maybe , maybe not) I'll head down to the lab and see whats really goin on .
-beerjet-
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The G.M. steel cranks can handle alot.
Look for casting # 7416...This crank is factory
nitrided and cross drilled by the factory.
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Do ya know the history of it? if not have it checked for cracks at a machine shop before purchasing.
Remember, metal has a memory! Make sure it's steel not cast.
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some k-boats still run the gm cranks. They just don't internally balance as easily as some of the Chinese cranks do. They take more mallory usually.
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Agreed..... Also steel cranks (at a glance) you can see the wide parting line.
also, cast cranks, have a very small parting line......
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The junkyard trick (I know I know) is to take the crank and rap it vertically on the concrete (lightly) on the output side of the crank, and if not cracked it will ring a very pretty (GAY) tune...steel cranks have no slag, and are brighter than cast ones...
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Agreed..... Also steel cranks (at a glance) you can see the wide parting line.
also, cast cranks, have a very small parting line......
I've heard that also . Actually , that's been the only way (that I've heard ) at a glance to tell .
-beerjet-
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hay Omar, I didn't know you could dance like that!!! By the way, you definitly have a cast crank with such a small lump in those tight blue speedos!!! O0
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It's not about what kind of crank rick . It's in the stroke . ;) :-*
-beerjet-