Thread: cast vs forged cranshaft 454

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ive got two cast marine cranks and a stock crank and was wondering what the difference between the two types are if any and how much hp. can a stock crank take

kodiak, here are 256 threads dealing with the BB Chevy. I don't have that much experience with the BB, but you can probably find your answer here...
http://www.clubhotrod.com/forums/for...?s=&forumid=29

I have read that cast BB cranks can be used in engines up to 700 HP.....I have several aquaintances that have race only cars and use cast cranks. They're plenty strong enough for all but an all out race engine....or if bragging rights are very important, go for a forged.

i have built engine big blocks that made big hp on cast cranks they work fine to 600 hp . hears some things to think about cast cranks when hit with a hammer they don t ring like steel crank that is harmonics cast do not ring as much so they do not trans harmonic like steel.this runs thru the engine not good. but cast cranks do not like to much twisting.a cam with 4 7 swap can help this .if you think you need a steel crank think a bout this .oil running clearance on rods@mains and bearing type

thanks for the info its greatly apperciated

Remember too....cast cranks are in or have been in about 95% of engines built. No offense meant to Pat, but what do harmonics have to do with this? I know what they are, but I've never heard this argument. Also, what does a cam swap have to do with twisting? The purpose of a crank is to turn linear motion into "twisting" motion, so isnt that what it's supposed to do? And bearing clearances are the same as far as I know....Please explain all this, I would be interested to hear.

how much time do you have ? how many big blocks have you built ? i have built over 100 of them from 369 to 600+so here is big block 101 . steel cranks ring like a bell .thats harmonics bad if not dampen .look at it is way less amplitude of harmonics is a good thing cast cranks hase less harmonices it will not ring like steel you say no big deal ?? busted valve springs some times is harmonices . I will not use gear drives. this sends harmonics thur crank to cam thur lifters to springs .you said stock engine have cast cranks .yes that right . but do they make 600 hp ?? cast cranks do not like to be twisted ? you said crank are made to be twisted that s rigth but are they running up 6800 rpm and 600hp? they are things to do to keep the cast crank alive like 4-7swap this is good for 20 hp helps crankshaft deflections =twisting .the 5 -7 firing order it is hard on the cranks .steel @cast so hey fix it 4-7 swap and it good for 20 hp ?and it cut s down on crank deflection =twisting all thing s I think of when i bulid a 600hp big block and more.I do not give bad info. all my info can be back up.if you dont think it right. i will keep it to my self .and you can learn the hard way. they are people who give bad info i am not one i have built big blocks for over 20 years .you said you never heard of this? good engine builder dont tell you evey thing .

Well, I have not built anywhere near 100 engines....only a few big blocks and several small blocks...all chevy. Let me first say that I havn't read much on the 4/7 cam swap, so I wont even comment on what I dont know about for certain. I will, however, read up on it now, then I will be informed! So, I still dont get what you're trying to say about cranks....are you supporting steel cranks, or cast cranks? The harmonics argument is worthless , we all know there are harmonics, but there has never been any definitive PROOF that any damage was caused solely by harmonics. The "gear drives cause cam wear" has been around for as long as gear drives have...has anything ever been proven beyond a doubt to be caused by gear drive?? No, never. I dont use them either, but Im not worried about harmonics, I just dont like the sound of them.

I also read your post on oil clearances, and Im sorry, but it makes no sense whatsoever...I dont know what you're trying to get across to us. I expected to see some bearing clearances mentioned so I can compare, but you dont mention any at all.

Pat, please read my original post again. I never said you gave bad info, and Im not saying you should keep it to yourself. Believe me, I have learned many lessons the hard way. And even though I may disagree with much of what you are saying, I most strongly disagree with your last statement, "good engine builders dont tell you everything"............Wrong, a good engine builder WILL tell you everything. I guess we can just agree to disagree!

here it is jonny.I like like cast it will not tran s harmonics like steel . but you say cam will not see wear it is a steel or iron stick harmonics can and do run thur it and it will break springs a belt drive dose not why? it is a belt ? no steel teeth or steel chain .do you see somthing here? steel . not all gear drives use steel gear aluminum or phenolic with one steel or iron gear this less harmonics so do you see this ? belt phenolic and polymer do not tran s hamonics .you said you don.t use them for the noise ? In that noise is harmonics . I do not know any good engine builder to put more harmonics in ? if you can t see it or smell it dose not make it there ? I like to think about things like this when building race type engines .you want running oil clearances ? what type of engine are you building ? you say i told you nothing . i told you where to put housing bores ? and why?? and bearing I like . all this time i have spent trying to help someone??why you do not like answers ? you want cut and dry answers building engine is not .if they made a cast iron crank that can take 750 hp up i would use them so steel is it rigth know .so for a street engine i would use a cast crank. but the 4-7 swap. can help why not do this ??l look at crank damper take i t off and throw it out and if it hase spring s damper take them out throw out to and if you fined somthing that help vibration dissipation dont think about it ??? I think i am a dam good engine builder and many people think so they have my engines why have i spent time with this with you ?? it may make you think or help somone else

Having been a vibration analyst for some years at the plant I retired from, harmonics are bad news, and to detailed to explain here. Maybe this will help some.
Crank Harmonics