Bbc forged crank with grooved mains? - Chevelle Tech
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post #1 of 18 (permalink) Old Dec 8th, 19, 5:53 PM Thread Starter
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Jani Heino
 
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Bbc forged crank with grooved mains?

What **** is this. Any pros and cons about this grooved crank.
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post #2 of 18 (permalink) Old Dec 8th, 19, 7:39 PM
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Re: Bbc forged crank with grooved mains?

Cons - Stress raiser!, reduced bearing area.
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post #3 of 18 (permalink) Old Dec 8th, 19, 8:19 PM
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Re: Bbc forged crank with grooved mains?

Years ago we did this, theory being to assure better oiling to the bearings.

Ran those engines hard, shifting at 7500 RPM, never had a crank failure.

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post #4 of 18 (permalink) Old Dec 8th, 19, 9:52 PM
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Re: Bbc forged crank with grooved mains?

Looks like a cast crank to me unless the photo is deceiving.

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post #5 of 18 (permalink) Old Dec 9th, 19, 2:44 AM Thread Starter
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Quote:
Originally Posted by BillK View Post
Looks like a cast crank to me unless the photo is deceiving.
Seller claims that this is gm forged crank,
I dont have the casting numbers yet.
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post #6 of 18 (permalink) Old Dec 9th, 19, 8:45 AM
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Re: Bbc forged crank with grooved mains?

have seller sell it to somebody else. That's a garbage deal left over from the 50's.

Strength of an oil film is dependent on the area. there's reasons why nobody grooves cranks or bearings anymore. good reasons,

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post #7 of 18 (permalink) Old Dec 9th, 19, 10:51 AM Thread Starter
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Quote:
Originally Posted by Tom Mobley View Post
have seller sell it to somebody else. That's a garbage deal left over from the 50's.

Strength of an oil film is dependent on the area. there's reasons why nobody grooves cranks or bearings anymore. good reasons,
Sounds great. Thats is only forged crank i have found here in Finnland that is for sale.
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post #8 of 18 (permalink) Old Dec 9th, 19, 11:01 AM
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Re: Bbc forged crank with grooved mains?

Can you post a few more photos, preferably of the entire crank shaft from a couple of different sides?? If we can see the parting line on it, then we can most likely determine if it is cast or forged.

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post #9 of 18 (permalink) Old Dec 9th, 19, 11:58 AM Thread Starter
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Re: Bbc forged crank with grooved mains?

Quote:
Originally Posted by WakkoWarner View Post
Can you post a few more photos, preferably of the entire crank shaft from a couple of different sides?? If we can see the parting line on it, then we can most likely determine if it is cast or forged.
will post more pictures when get some.
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post #10 of 18 (permalink) Old Dec 9th, 19, 12:05 PM Thread Starter
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Re: Bbc forged crank with grooved mains?

Tale goes like this, these were grooved by gm machinists to use in early 70s LS6 engines instead of crossthrilled cranks. can also be found from early Hardin marine bbc engines.
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post #11 of 18 (permalink) Old Dec 9th, 19, 1:10 PM
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Re: Bbc forged crank with grooved mains?

When did manufacturers and/or OEM start grooving the top (unloaded) main bearing shell?

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post #12 of 18 (permalink) Old Dec 9th, 19, 1:54 PM
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Re: Bbc forged crank with grooved mains?

Quote:
Originally Posted by Janih View Post
Sounds great. Thats is only forged crank i have found here in Finnland that is for sale.

Not much help, but if you want to come to Indiana, I have a good, factory, from a running engine, never reground forged Mark IV 454 crank I'll make you a deal on.
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post #13 of 18 (permalink) Old Dec 9th, 19, 3:07 PM
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Re: Bbc forged crank with grooved mains?

I was thinking if that groove wasn't too deep and the crank was still at standard size then maybe it could be machined out but that groove looks to be too deep to machine out.
What's the most a crank could be cut to fix some damage ?

John
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post #14 of 18 (permalink) Old Dec 9th, 19, 4:02 PM
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Re: Bbc forged crank with grooved mains?

If it's a steelie, there's no reason it couldn't be welded up and turned.
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post #15 of 18 (permalink) Old Dec 9th, 19, 6:40 PM
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Re: Bbc forged crank with grooved mains?

The general consensus has always been to never groove a Chevy Crank, you cross drill instead.

The older publication, “How to Hotrod Big Block Chevys” had some figures stating that you cut the load carrying capacity of the mains by as much as 30% when grooving that Main journal.

As for steel or cast, just look at the forward crank throw. If it has a large flat forge line, it’s a steel forging. If the line is really thin, it’s a cast modular iron crank.


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