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Discussion Starter · #1 ·
Just got a 383 stroker crate motor from a friend. I'm putting a four speed behind this engine. It is a 4 in. bore with a 3.80 stroke. I was wondering if the motor is internally balanced. The flywheel that he gave me came with the motor, but looks like a stock 350 one. Any help would be appreciated.
 

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Thing is, a 383 is usually externally balanced. But it can be internally balanced at extra expense. If it's externally balanced, usually you'll need a flywheel for a 400 SBC. The only way to know is to contact the original builder, or tear it down and have it balanced or balance checked by your engine builder/machine shop.

This is one reason never to give premium or even average dollar for an engine like this unless these kinds of things are known prior to the sale.
 

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Discussion Starter · #4 ·
This motor was delivered to my house from the Chevy dealership where I live. The motor was supposed to be turn key but arrived with all the externals not attached. It is a true crate motor from GM. Has all the components with the motor, the flywheel came a couple of days later. The thing that throws me off is the 3.75 stroke (old 400) vs. the 3.80 stroke. I guess I could call the dealer and ask if the new 383's are internal or externally balanced.
 

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Trifive Automotive Electrical Wiring Expert
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Just got a 383 stroker crate motor from a friend. I'm putting a four speed behind this engine. It is a 4 in. bore with a 3.80 stroke. I was wondering if the motor is internally balanced. The flywheel that he gave me came with the motor, but looks like a stock 350 one. Any help would be appreciated.
Is this a GMPP crate engine? Does it have a 1 piece rear main seal? What's the casting number? According to a note in the General Motors Performance Catalog.....
IMPORTANT! All Chevy small-block and big-block engines with one-piece crankshaft seal require an externally balanced flywheel or flexplate.
 

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"I guess I could call the dealer and ask if the new 383's are internal or externally balanced."

Don't guess, don't ask us, just do it. Maybe call two dealers. Better yet, call two of the dealers that sell a ton of these, like Scoggin Dickey or Pace or Gilbert. My money is on the weighted flywheel.

Why do it any other way?

Then you could tell us, and not ask us.
 

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Discussion Starter · #8 ·
"I guess I could call the dealer and ask if the new 383's are internal or externally balanced."

Don't guess, don't ask us, just do it. Maybe call two dealers. Better yet, call two of the dealers that sell a ton of these, like Scoggin Dickey or Pace or Gilbert. My money is on the weighted flywheel.

Why do it any other way?

Then you could tell us, and not ask us.
Rick, I thought this forum was to ask questions for help. I guess, I mean I know I'm wrong. I'll call probably 10, I'm sorry, I WILL call 10 at this point and let you know.
 

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The gm 383 crate engine is 1/2 externally ballanced like all 1 piece seal sbc engines. The 383 uses the same flywheel as the same as the other gm crate engines. the GMPP 383 is 4.00 bore and 3.80 stroke gm uses this combo because it makes more torque than the old style aftermarket 383 combos and is a std bore. the old style actually has to be 4.060 bore to get 383 with the 3.75 stroke crank . personally I have had both and the gm piece is smoother and I think a little better and quieter as well . :party0031::happy0030::)
 

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Unless you are spending around 3000 for the crankshaft (being cutom made) ALL one piece rears are external balance. You can find internal balanced flywheel/flexplate for a one piece crank - but they all (unless cheap China parts) have the warning that they will not work on "stock" one piece seal crankshafts!
 

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Trifive Automotive Electrical Wiring Expert
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One piece seal crankshafts have a different bolt pattern than 2 piece seal cranks, so it's hard to put the wrong flywheel/flexplate on them. :)
 

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You are very correct Don, in fact its impossible to use a two piece on a one piece or visce-versa (not just hard)..
But I thought the q wasn't about the plate - it was about int\ext - you can find all four types - 1pc int (Custom crank only), 1 pc ext, 2 pc int, 2pc ext. so I used the plate application to demonstrate that all stock 1pc are externals. Maybe I mis understood the question?
 

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YOU got it

The Chevy crate motor has a 4.00 bore and 3.8 so they could get their 383" with a std. bore block . this shoulld be a 1 pc seal block with 4340 crank. 1 pc seal requires smaller bolt circle so standard cirle flywheels won't bolt up and I believe they only make one flywheel for one piece blocks . so I think if it bolts up It's the right one.:happy0030:
 

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That really makes sense! How do you tell when it installed? Even my boney little fingers can't behind it to feel the fat part (that just sounds soooo wrong)
 

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Discussion Starter · #19 ·
Thanks for all the input guys. I called Scoggins and Dickey and the one that was sent was the correct flywheel. It's a shame, my buddy paid for a turn key motor and when it comes in pieces you have a tendency to wonder if all the right parts came for the motor.
I did find out that the water pump sent is for a standard rotation cooling system but the brackets that were sent are for a reverse water flow system. (water pump pulley wouldn't fit the water pump),
Thats for all the help.
 
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