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1986c10 10-07-2012 07:23 PM

BBC crank identification help
 
Hi, ive got a 396 i believe crank with a casting number of 3804815. I cant find anything to match those numbers, ive found 3804816 and 3904815 but not what mine shows, here is a pic of it. Just trying to see if its cast or forged so i can sell the rotating assembly i have lying around. Thanks in advance!

http://i18.photobucket.com/albums/b1...o/IMAG0494.jpg

http://i18.photobucket.com/albums/b1...o/IMAG0491.jpg

BOBCRMAN@aol.com 10-07-2012 07:38 PM

Can't tell because of angle/clarity of pics. Don't have my crank book with me. Looks like cast.

Rule of thumb. If the parting line on the side of the crank throw is only a line, up to 1/16" wide it is a casting. If the line is 1/4" plus and looks like it has grind marks on it. It is forged.

Stand crank on end, on a shop towel. Rap a counter weight with a hammer. If it goes "thunk" it is cast. If it rings clearly, like a bell, it is a forging.

1986c10 10-07-2012 07:53 PM

Thanks bob i think its cast also, im at school now so i cant take a better look at it to tell but i think i remember the parting line being very thin so its probably cast. What would would be a good selling price for the whole assembly, 10/10 crank, forged trw pistons on gm rods, its a 427 rotating assembly all fresh but has sat for awhile.

1986c10 10-07-2012 07:55 PM

In the bottom pic, you can kind of see on the bottom throw what looks like grind marks like it has been clearanced or something, would this be a mark of the forging process you were talking about if its not cast? Thanks again

BOBCRMAN@aol.com 10-07-2012 08:08 PM

Hard to say on price. I can't sell 396-427 stuff. Everybody around here wants 454-500+ stuff even tho they can't afford it.

Prices here, good crank cast $150.00
rods, good bolts recon $200.00
Old TRW forgings around $200.00

1986c10 10-07-2012 09:55 PM

Yeah i kind of figured that, well i'll try selling the stuff for the prices you listed and see what happens haha. Thanks again Bob! Anyone who might be able to identify the crank by the number id really appreciate it. Thanks

1932bantam 10-08-2012 09:37 AM

third counterweight on a 396 is 3/4 on a 427 it is 7/8 hope this helps

1986c10 10-08-2012 01:16 PM

I was told it was a 427 rotating assembly so i assumed he just had a 396 crank and rods laying around as well as a 454 block so he made it a 427 + .030 assembly. When you say the different sizes, you are referring to the counterweight thickness correct?

66GMC 10-08-2012 03:10 PM

Quote:

Originally Posted by BOBCRMAN@aol.com (Post 1597019)
Can't tell because of angle/clarity of pics. Don't have my crank book with me. Looks like cast.

Rule of thumb. If the parting line on the side of the crank throw is only a line, up to 1/16" wide it is a casting. If the line is 1/4" plus and looks like it has grind marks on it. It is forged.

Stand crank on end, on a shop towel. Rap a counter weight with a hammer. If it goes "thunk" it is cast. If it rings clearly, like a bell, it is a forging.

Pics and more info fom BBC Parts Interchange Manual.

1932bantam 10-08-2012 03:15 PM

yes the thickness of third counterweight. 396 has a lighter rotating assembly if it is a 396 crank and making a 427 using 454 block probably should have everything balanced for longevity. you can't mistake steel crank. it has a wide parting line. just put a 3/4 end wrench on it it will either fit or not

1986c10 10-08-2012 03:56 PM

okay, thanks 1932 batman. I will check it out next time im home but i believe it to be a cast 396 crank not sure why nothing matches the casting numbers though... Its all balanced and im trying to sell the whole assembly to get a 489 kit.

1986c10 07-23-2013 04:50 PM

Sorry its been awhile, it has a wide parting line like a cast but rings if i hit a counter weight with a hammer lightly like a forged...

66GMC 07-23-2013 07:07 PM

Quote:

Originally Posted by 1986c10 (Post 1697228)
Sorry its been awhile, it has a wide parting line like a cast but rings if i hit a counter weight with a hammer lightly like a forged...

Read it again ...

Quote:

Rule of thumb. If the parting line on the side of the crank throw is only a line, up to 1/16" wide it is a casting. If the line is 1/4" plus and looks like it has grind marks on it. It is forged.

Stand crank on end, on a shop towel. Rap a counter weight with a hammer. If it goes "thunk" it is cast. If it rings clearly, like a bell, it is a forging.
WIDE parting line = forged

Rings like a bell = forged

3804815 = forged

366T/396/402/427/427T 3.76" stroke.

1986c10 07-23-2013 07:39 PM

Shoot, i think i meant to say it had a thin casting mark like a non forged. Now im just confusing myself. If that casting number comes back as forged like you said then it must be forged. Yippee! thanks man! Now to decide whether this short stroke higher rev combo will live in a studded 2 bolt or to try and sell it and get the 489 kit that I really want...

66GMC 07-23-2013 09:09 PM

FWIW ... I had a new Scat cast crank 910454 installed and balanced in my 2-bolt main 454.

My machinist "guarantold me" that I wouldn't have a problem running my engine up to 7,000 RPM, and I have read much the same on many internet forums.

David Vizard, author of How To Build Chevy Big Blocks on a Budget seems to have good things to say about them, too.

According to him ... (page 32)
A GM factory Forged Steel crank (like yours) has 120,000 PSI strength
A GM factory Cast Steel crank has 80,000 PSI strength
and a Scat 900 Cast Steel crank has a 110,000 PSI strength.


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