BBC how to tell steel from cast crank?? - Team Camaro Tech
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post #1 of 13 (permalink) Old Jan 9th, 07, 02:44 PM Thread Starter
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BBC how to tell steel from cast crank??

I was just told by a machine shop that I have a steel crank but I thought it was a cast. How do you tell the difference????? The only numbers I could find were GM1 13.
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post #2 of 13 (permalink) Old Jan 9th, 07, 02:52 PM
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Re: BBC how to tell steel from cast crank??

A forged crank will have a wide parting line that's like 3/8's to a 1/2" wide due to when the excess metal was cut off it from the forging operation.

A cast crank will have a real narrow parting line like less than an 1/8th inch wide.

And you can tap a counterweight on a forged crank with a small ball-pein Ford tool and it will ring like a bell whereas a cast crank kinda just goes thud!!

pdq67
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post #3 of 13 (permalink) Old Jan 9th, 07, 04:37 PM Thread Starter
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Re: BBC how to tell steel from cast crank??

Nice!!!! That baby has a 1/2 mark all the way down the crank!!! Can you say "bonus"?? Thanks guys!
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post #4 of 13 (permalink) Old Jan 9th, 07, 05:07 PM
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Cool Re: BBC how to tell steel from cast crank??

They say a picture is worth a thousand words, so here are a few hundred because the images aren't that great.

Note the parting line on this Scat Chevy Cast 383 crank on the counter weight by the 5-6 throw and again on the flywheel flange. It appears as a straight narrow line.

SCAT Cast Crank


This is the standard stock cast iron crankshaft I pulled out of my old SBC 400 before I replaced everything but the '509 block. It can be enlarged enough to see the parting line if you down load it and blow it up as it is a fairly large image (unless photobucket shrank it as I'm a little fuzzy on image size upload down load thing).

Stock Cast SBC 400 crank


This is an Eagle Non-Twist forged crank. Note that the parting line, even though it has been ground down, lies in a straight line from one end of the crank to the other going through the counter weights and crank throws.

Non Twist Forged Crank


Compare that to an old magazine photo (sorry about the dithering) which shows a stock 5140 forged steel crank that was twisted to bend the crank throws 90 out going down the line. You can see the heavy parting line clearly going right through the main journal crossing it at a 45 angle. This is a good example of a forged parting line and why a non-twist crank is preferable.

427 Factory Forged Crank twisted



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post #5 of 13 (permalink) Old Jan 9th, 07, 07:25 PM
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Re: BBC how to tell steel from cast crank??

Have some fun!
Stand the crank on a rag, then strike one of the counterweights with a hammer. Don't worry, you aren't going to hurt it with a hammer tap.
It should ring like a bell!
David

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post #6 of 13 (permalink) Old Jan 9th, 07, 08:04 PM
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Re: BBC how to tell steel from cast crank??

Quote:
Originally Posted by Larger Dave View Post







Larger Dave
That would make a great end table and look great next to any recliner !

my Magnaflow X-pipe system sound clip, click the link

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post #7 of 13 (permalink) Old Jan 9th, 07, 09:16 PM
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Re: BBC how to tell steel from cast crank??

Or a redneck lawn ornament
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post #8 of 13 (permalink) Old Jan 9th, 07, 09:36 PM
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Re: BBC how to tell steel from cast crank??

The old tapping hammer is the only tool you need.

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post #9 of 13 (permalink) Old Jan 10th, 07, 09:28 AM
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Re: BBC how to tell steel from cast crank??

Ding, Ding, Ding!!

Morris, it's din, din time!!

He, He!!

pdq67

PS., anybody remember the old "Morris the Cat" commercials?
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post #10 of 13 (permalink) Old Jan 10th, 07, 10:00 AM
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Re: BBC how to tell steel from cast crank??

So many baby boomers on this site Im sure most of us do

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post #11 of 13 (permalink) Old Jan 10th, 07, 12:57 PM
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Re: BBC how to tell steel from cast crank??

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Originally Posted by pdq67 View Post
anybody remember the old "Morris the Cat" commercials?
I do.
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post #12 of 13 (permalink) Old Jan 10th, 07, 02:50 PM
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Re: BBC how to tell steel from cast crank??

I've had a few cast cranks that rang like a bell, too. Parting line is your best bet for telling what you have. I've gotten to the point where I can look at the back flange on one and tell without having to pull the pan. This doesn't work on the late model 1-piece rear main stuff, though.

Gary Adrian
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post #13 of 13 (permalink) Old Jan 10th, 07, 07:33 PM
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Re: BBC how to tell steel from cast crank??

Right you are Gary, the dam things are round with no "fans" on them anymore..

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