400 SBC question!!

[disorder_in_dminor]

Im pretty sure my 400 is externally balanced by the harmonic balancer and the flex plate, my flex plate is getting really shitty and i need to put my new flex plate (the one off my blown up 334 {305,400 crank) onto the car. When i stroked my 305 I bought the flexplate and it barely seen any use but i noted it had counter weights and stuff on them.


So i guess my question is everytime i change the flexplate on a 400 do i have to get the rotating assembly balanced????

 

[R/T kota]

yes the 400 is externaly balanced
No you dont have to balance the rotating assembly

 

[85 Cutlass Brougham]

No need to rebalance it so long as it was originally balanced for a 400 crank. It uses a standard imbalance weight, like a SBF, so the external parts are standardized.

 

[disorder_in_dminor]

most excellent!

So im pretty sure i can change the flexplate with the engine and trans still in the vehicle, i just need to undo the bolts at the torque converter then at the back of the crank.

 

[pontiacgp]

all cranks which use a one-piece seal require a counterweighted flywheel for proper engine balance....with a two seal it's always internally balanced...

 

[85 Cutlass Brougham]

Well, no. The 400 is the exception to this rule. The 400 crank is externally balanced while the :262,265,267, 283, 302, 305, 307, 327, and 350 are all internally balanced with neutral balance flywheels.

 

[pontiacgp]

Well, no. The 400 is the exception to this rule.

your right and thanks ...