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3751877 A cast 383 Crankshaft?

rickseeman

rickseeman

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This crank came to me in a 383. It had a neutral balancer on it. The guy said it ran fine. But it's a cast crank and I thought cast cranks had offset weighted balancers. I think it must be a 400 crank. When I research it the results I get are 383 or 400. I realize 383 and 400 cranks fit the same but I thought the 400 takes an offset balancer. This is all very confusing to me. So I think I should use a 400 balancer? What about the rods? Are they part of that deal? I never said I was a wedge expert. Thanks.
 
Yes, the 71 2bbl 383 cast, 400, 440 cast all use the same weight. The balancer is just physically thicker on the 440. Rods are all the same.
 
Screenshot_20250707_170956_Chrome.jpg
 
OK, thank you for the info. Now it all makes sense. (I think the guy was stretching the truth when he said it ran good.)
 
the 70-71 cast crank 383 used the 3577180 balancer. It was only used for 2 years on the 383 only.
 
pnora said:
the 70-71 cast crank 383 used the 3577180 balancer. It was only used for 2 years on the 383 only.
Click to expand...
I hope this crank casting number isn't the one that takes a 2 year only balancer. I'm hoping it's a 400 crank so finding a balancer will be easy.
 
rickseeman said:
I hope this crank casting number isn't the one that takes a 2 year only balancer. I'm hoping it's a 400 crank so finding a balancer will be easy.
Click to expand...
Before you reinvent the wheel, you should figure out if the balance is RIGHT for the parts its already assembled with (or the parts you intend to build it with). Just sayin....
 
I don't know how to figure out the balance. Just trying to do a stock part build but when you get into a situation where there is cast cranks and they take a different balancer and flexplate and the previous owner has a cast crank and a neutral balancer it becomes very confusing. I'm hoping somebody says that number is a 400 crank and then it will be easier.
 
The number 3751877 is well into the 1974 range. Based on that I would think it is a 400 crank most likely 74 or newer. This is from the 74 parts manual.

Screenshot 2025-07-07 215747.png
 
YES, that is what I needed. I thought a casting number starting in 37 would not be a 70 or 71. Thank you for the help. Now I think I can proceed. I have lots of 426 Hemi data but that doesn't help me if I'm working on a 383 from the 70's.
 
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