topdog

I'm building a 383 for my Z. Questions is the balancer. I know I need an external balancer but I don't quite understand the relationship between the flexplate and balancer and cran. The rotating assenbly was "balanced" but I belive that refers to the pistons and rods being balanced not the crank. Am I right on this? Does the entire assembly need to be balanced or does the flex plat get balanced (like a wheel would) and the balancer take out any unwanted vibration.
Help!!! I don't want to implode this new motor...

92heritageRS

Check this out http://www.centuryperformance.com/balancing.asp

As for the flex plate balance you are refering to the internal/extrenal balancing. A 400 is externally balanced. Chevy chose to offset the crank throw with weights on the balancer and flywheel/flexpalte outside the engine. All other small blocks were internally balanced were the flexplate/flywheel and harmonic balancer are neutral. In a 383 if you use a stock 400 crank your engine that was internally balanced when it was a 350 now becomes externally balanced. The 383 then will need new balancer and flexplate. This balance has nothing to do with the proccess of weighing the internals and actually balancing the rotating assembly.

http://www.babcox.com/editorial/ar/eb10330.htm

five7kid

iTrader: (14)

There are some generalizations there that need to be clarified.

One-piece rear main seal cranks do not use a neutrally balanced flexplate. However, it is still different than the 400's "external balance" flexplate, and the 305/350's with one-piece rear main seals are still considered "internally" balanced - the damper on the front of the engine is still neutrally balanced.

As for 400's being externally balanced, that isn't always true, either. There are aftermarketers that are making internally-balanced 3.75" stroke cranks for 383's, especially one-piece rear main type cranks. So, you really need to understand what they are selling you.

When the rotating assembly is balanced, the flexplate and damper may be installed, but they should not be modified as part of the balancing process. Their "balance" should be standardized, and if not modified, they can be replaced later if necessary without having to rebalance the entire rotating assembly. If they are modified in order to achieve rotating assembly balance, then the entire assembly will have to be rebalanced if they need to be replaced.

92heritageRS

Five7 is right. I was just keeping it as simple as possible. No intent to miss lead anyone. My Scat 9000 3.75 stroker crank is one piece rear main and internal balance. Thanks for clearing up the gaps for me.

topdog

Thanks for the help guys!! I will ask some questions and make sure...can't wait to get this on the duno and then in the car!!

topdog

DYNO not duno ...lol