External balanced stock flywheel

S

Surfer69

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Nov 13, 2009
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Manhattan Beach, CA
My 383 is internal balanced and I'm using a thin flywheel I got off Ebay that I assume must be internal also. Lost the info on it.

I would like to go back to stock flywheel but they all say external. Does anyone know how to find an internal balanced stock flywheel? My crank and HB are internal. What options do I have?
 
On a Flywheel, for a stick shift I can't help, but on a FLEXplate for a automatic, I suspect you can knock off that added balance weight.....

I know nothing beyond that....


:drink:
 
Your probably right Carb. My problem is Summit only shows 1 stock GM 168 flywheel for a 350 and it says external. Zip and Ecklers show basically the same stock flywheel but don't say anything about the balance.

So not sure what to believe.
 
Sometimes they refer to them as neutral balance, this is internal as all the older Chevy Motors except for the 305 and 454 were internal balance, this is way back before 1974, not sure after. Best bet is a quick phone call, The should still be out there everywhere. Any of the Clutch Suppliers should be able to help you out.
 
Surfer69 said:
Your probably right Carb. My problem is Summit only shows 1 stock GM 168 flywheel for a 350 and it says external. Zip and Ecklers show basically the same stock flywheel but don't say anything about the balance.

So not sure what to believe.
Click to expand...

Years ago a machine shop owner/friend explained why the differences, and so it involved something about no room for a counterweight on the inside of the blocks between the last journal and the block.....or first journal and block in front....so at that time he said that desire to shorten the block casting was the reason it was externally balanced....saved about 2"? of block length and weight.....

that is the way I remember what he said.....

I always take the short blocks to the shop to be rebuilt, and don't worry over it much....HIS problem....:bump:

that is my best remember over, but I don't remember what block we were looking at it was a V8, that's all I remember...sorry...

:clobbered:
 
Carb Doc said:
Stock GM Flywheel for a 350 . or a 396 or 427 BB are internal balanced.
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I don't think the 350 SB's are internally balanced. I have a ZZ4 and it's not internally balanced. Believe me. It came with a flexplate and I had to find a flywheel for it.

If you want a flywheel, just dial up McLeod on their webpage. To select a flywheel, you have to have in mind, the year that the small block transitioned from the old traditional two piece rear crank oil seal to the newer "one piece" oil seal. What year was your SB manufactured? If you look at the newer SB blocks, the newer oil seals have an aluminum circular machine part for the oil seal. The flywheel has to be compatible with the rear oil seal configuration. One, thing...for the older two piece crank oil seal SB blocks, a 327 flywheel will work...it's for an internally balanced engine.

For the newer one piece oil seal SB blocks, I think McLeod sells "neutral balance" flywheels that have adapter kits that include various weights to bolt onto the flywheel to achieve balance.

Congratulations for having a 383 internally balanced engine!!! When I bought my ZZ4 350 engine, for whatever reason, I thought it was internally balanced. I was very disappointed to find out it wasn't. I think high performance engines should be internally balanced.
 
Flywheel & Flexplate Balance Requirements

When discussing the stock Gen 1 SBC, all were internally balanced and take a neutrally balanced flywheel EXCEPT the 400. The 383 can be either because it's an aftermarket mod. In this case, use of 5.565" or 5.7" rods on the 3.75" stroke crank usually requires external balance like the 400 SBC because the internal counterweight can't be bigger and still clear the piston at BDC (unless expensive Mallory metal is used).

On the other hand, rotating kits which use 6" connecting rods have additional clearance; most are internally balanced and can use flywheels/flexplates from 350s, 327s, 302s, 283s; and also from neutrally balanced BBCs such as the 396, 402, and 427 since they all share the same bolt circle and tooth counts (153 and 168).

With BBCs, the stock 396, 402 and 427 use the same flywheels as the Gen 1 SBCs and have the same 3.58" bolt circle, but the 454 is an externally balanced engine like the 400 (not the same balance spec, however). Both the 400 and the 454 also require an externally balanced harmonic damper.

With the advent of the one-piece rear main seal (Gen 2 SBC), the end of the crank had to have a different diameter and be circular so no scalloped crank flange was possible. Because offset weight was lost at the back end of the crank, the flywheel/flexplates for the 350s are externally balanced to make up the difference, but these engines still use a neutrally balanced harmonic damper. Also, the bolt circle for the one-piece rear main seal cranks has a smaller bolt circle so it can't be used incorrectly on a Gen 1 (two-piece rear main seal) engine.

I haven't researched the ZZ crate engines, so can't comment on them in this discussion.

Hope this helps!

:3rd:
 
my 383 1pc rms has a external balance flywheel. I built the engine 5 years ago, at that time I found int and ext balanced flywheels.

I wonder if a ext balanced flywheel can be drilled to remove mass so that the balance is neutral. Actually I wonder if a ext balance flywheel undrilled and brandnew is balanced neutral, it probably is - then it should be good for any internal balanced rotating assembly - not ?? am I missing something here ??
 
MYBAD79 said:
my 383 1pc rms has a external balance flywheel. I built the engine 5 years ago, at that time I found int and ext balanced flywheels.

I wonder if a ext balanced flywheel can be drilled to remove mass so that the balance is neutral. Actually I wonder if a ext balance flywheel undrilled and brandnew is balanced neutral, it probably is - then it should be good for any internal balanced rotating assembly - not ?? am I missing something here ??
Click to expand...

I was going to say something like that, but didn't want to get into something I didn't know jack about....I would say to fill in the balancing holes drilled in the back of the fly.....get the machine shop to neutral balance the thing....

should be easy, I would think.....maybe drill/remove similar weight from other side until balanced??

:p:beer:
 
To change the balance on any flywheel, one can add weight or remove weight, or both. If your rotating assembly is not stock, you should have the whole assembly, including the flywheel or flexplate, and the harmonic damper, balanced by a competent machine shop.
 
Mine's a 2 piece.

I just want to make sure it's nuetral/internal when I buy. If it's symetric with no weights on it then I would think you could assume it's internal if not stated specifically.
 
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