Are the late model >87 SBC 305/350 internal or externally balanced?
08-17-2005, 11:38 AM
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Engine: 360 .060 over TPI
Transmission: T-5
Are the late model >87 SBC 305/350 internal or externally balanced?
I remmber reading some where!! that the GEN 1 SBC with the single piece rear main seal in externally balanced? is this true or not? I am haveing to rebuild mine and wnat to upgrae the harmonic ballancer and possibly go to an aluminum flywheel.
thanks
steve
thanks
steve
08-17-2005, 11:42 AM
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Car: 1984 Z28 Hardtop
Engine: 383 Carb
Transmission: 4L60
Axle/Gears: 3.54 Dana 44
The only factory Gen I SBCs that were externally balanced were the 400s. All others are internally balanced.
08-17-2005, 11:46 AM
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Car: clapped out 84Z
Engine: 355 efi roller
Transmission: tremec TKO
Internally balanced. The flywheel does have an external counterweight on it due to the one piece rear seal, but the engine is internally balanced.
08-17-2005, 12:04 PM
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Car: 82 Berlinetta/57 Bel Air
Engine: LS1/LQ4
Transmission: 4L60E/4L80E
Axle/Gears: 12B-3.73/9"-3.89
The harmonic damper will need to be a neutrally-balanced part.
The flywheel will need to be a one-piece rear main seal part, which means it will not be neutrally balanced. But, that doesn't mean it is the same as a 400 flywheel.
This whole "internal vs. external balance" thing with one-piece rear main seal cranks is kind of silly. Technically, two-piece rear main seal cranks were "externally balanced", because the counterweight was outside of the crankcase - but, it was part of the crank. However, since one-piece rear main seal cranks cannot have the counterweight outside of the crankcase, the factory chose to put a weight on the flexplates/unbalance the flywheel to provide that function. As stated, the 400 engines were "externally balanced", because the damper and flexplate/flywheel were weighted to complete the balancing.
The flywheel will need to be a one-piece rear main seal part, which means it will not be neutrally balanced. But, that doesn't mean it is the same as a 400 flywheel.
This whole "internal vs. external balance" thing with one-piece rear main seal cranks is kind of silly. Technically, two-piece rear main seal cranks were "externally balanced", because the counterweight was outside of the crankcase - but, it was part of the crank. However, since one-piece rear main seal cranks cannot have the counterweight outside of the crankcase, the factory chose to put a weight on the flexplates/unbalance the flywheel to provide that function. As stated, the 400 engines were "externally balanced", because the damper and flexplate/flywheel were weighted to complete the balancing.
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