Thread: Harmonic damper ?

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I have a Damper here that came off a 383 stroker, Is there a way to tell if it is for internal or external balance ?

A stock 400 sbc damper will have about a 1/2" groove in it about 1/2 way around

265-350 SB-Chevy Internal Balance 6-1/4'' Diameter
400 Chevy External Balance 7-1/4'' Diameter look on the back side for the counterweight.

Fluiddamper does offer a 7-1/4'' 265-350 SB-Chevy Internal Balance. so it becomes important to look at the back side in order to verify the part. Diameter is a quick way to tell, counter weight confirms the part.

if its off the crank---put a piece of pipe or metal rod thru the middle and see if its balanced or WAYYYYYY out of balance

Originally Posted by pepi

265-350 SB-Chevy Internal Balance 6-1/4'' Diameter
400 Chevy External Balance 7-1/4'' Diameter look on the back side for the counterweight.

Fluiddamper does offer a 7-1/4'' 265-350 SB-Chevy Internal Balance. so it becomes important to look at the back side in order to verify the part. Diameter is a quick way to tell, counter weight confirms the part.

There is no counterweight on the stock dampner, there is however counterweight on the stock flex plate. If you desire to use a manual tranny behind a stock 400 sbc you must use a flywheel from a 454. Been there, done that.

Its 8" dia,about 1.5 thick with a 3/4" w x 1/4 deep groove 1/2 way around ,no counter wt on the back

the outer ring on the 400 stock GM is scalloped out and is thicker were weight is needed so outer ring is not the same shape or a even thickness . so if no weigth in the inside of damper hub or not scalloped/under cut on the outer damper ring . its not external in the front

Fuzzy Pictures
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I'd call that external

That is a stock 400sbc dampner.

Originally Posted by NTFDAY

There is no counterweight on the stock dampner, there is however counterweight on the stock flex plate. If you desire to use a manual tranny behind a stock 400 sbc you must use a flywheel from a 454. Been there, done that.

Correct and that was the reason I listed the brand name Fluidampr, misspelling it btw. I do see I omitted that in the top of the post and that would be confusing.

Thank You
ED