external v. internal balanced engine

[lasvegas]

How do you tell if your small block is internally or externally balanced? I have the ZZ4 and do not know which it is. Can anyone help? I guess this makes a difference as to harmonic balancer, flywheel, gear drive choices . . .

 

[Triaged]

The only externally ballanced SBC is the 400. If you have a 383 most likely it is externally balanced (some custom cranks are internally ballanced). You can tell by the counter weight on the flywheel and the large section removed from the balancer.

'71 Blazer CST w/ a 400sbc, 4" lift, 36" Supper Swampers, and alot of rust
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[Neil]

ZZ4 is internally balanced.. 400 is only sb w/external &amp; will have counterweights on the flywheel and a big fat harmonic balancer..FYI..big blocks are externally balanced also.

Neil H. Alabama.. "It's a full size thang, Jeep owners don't understand!!" '78 K5 400ci 4x4 AT,AC,PW Cheyenne., '74 C10 4x2

 

[muddin4fun]

My 383 is externally balanced and it has weights on the fly wheel. I'll have to go look at my balancer again, I think it has a notch in it er somethin.

If you see my truck on a trailer, call 911 cause it's <font color=red>STOLEN!!!</font color=red>
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[thatK30guy]

FYI, only the 454 is externally balanced.

The 396, 402, 427's are all internally balanced.

<font color=red>I'm a "black top mudder"!!!</font color=red>

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[lasvegas]

my question comes up because the Chevy Hi-Po parts manual says that all the 86 and up one piece crankshaft seal crankshafts require a flywheel with counterweights. Is the counterweight to balance the flywheel or is it to balance the crank?

 

[michaelm]

look in the book, if it is the chev power manual pg5-18 fig 50, and you can see the counterweight at the flywheel flange on the old style cranks. one piece seal style are round there so they moved the weight to the flywheel. i will go with you and call that external.

 

[lasvegas]

Just so you know, I e-mailed General Motors (GMperformanceparts) or something like that and they e-mailed me back that the zz4 is "externally balanced". Hopefully that does not destroy your view of the universe. They also gave me some websites for looking up technical information on GM engines if anyone is interested.