TBI 350 internal or external balanced

budissy78 · January 24, 2006

I hoping someone knows for sure if a 1992 tbi 350 is internally or externally balanced. I dont have the flywheel or the harmonic balancer to tell by. Thanks in advance for the help.

tarantula · January 25, 2006

The last I knew, all 350s were internally balanced.

90GMCZ71 · January 25, 2006

The last I knew, all 350s were internally balanced.

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Yep, all are internally balanced from the factory.

Rookie · January 25, 2006

I beg to differ. 86 and newer went to a one piece rear main. When gm did this the lost part of the counter weight on the crank. So an 86 or newer fly/ flex plate will have a small counter weight on it. the balancers are the same. So as long as you get a flex/ flywheel for an 86 one piece rear main you should be good to go.

Mr. Smith · January 25, 2006

I beg to differ. 86 and newer went to a one piece rear main. When gm did this the lost part of the counter weight on the crank. So an 86 or newer fly/ flex plate will have a small counter weight on it. the balancers are the same. So as long as you get a flex/ flywheel for an 86 one piece rear main you should be good to go.

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Nope incorrect...

Engine never used that little hunk of metal where the flywheel bolts to account for total engine balance. If that were true then there would be no counterweights on the crank internally. Nor would those counterweight be drilled in various areas to obtain desired balance.

The harmonic balancer would be machined accordingly for engine balance.

All rotating parts have to be balance. The weight you speak of is not for engine balance. It is used to neutral balance the flex plate.

budissy78 · January 25, 2006

Thanks for all the help. I thought it was internally balanced because, when I took off the balancer I didn't see any counter wights. The only thing throwing me off was the weight on the flywheel but now I under stand. Again thanks for all the help.

Rookie · January 25, 2006

So what will happen then if you bolt a pre 86 to a post 86 it will be out of balance.

i rest my case, not that i was trying to prove a point just giving information.

90GMCZ71 · January 26, 2006

So what will happen then if you bolt a pre 86 to a post 86 it will be out of balance.
i rest my case, not that i was trying to prove a point just giving information.

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Well after a bit of reading on the net, it does look like the one piece rear seal engines are both internal and externally balanced. The balancer is internally balanced but because of the one piece rear seal, the flexplate/flywheel is externally balanced. I need to call my buddy that owns a machine shop to get the complete story.

//90GMCZ71