383 sbc

[chevyracer1960]

Have a 383 with balanced eagle assembly...it has a auto flexplate on it balanced and sfi...the front balancer is a stock 400 sbc balanced to flywheel I'm assuming...I want to replace this balancer and use a sfi balancer..question?? does it have to be rebalanced to flex plate?? I have a fairly new 350 sfi fluid balancer..was told it might work but not sure enough??

help needed

thanks

[Tod74]

balancer must be one for an external balanced 400 if that is what the crankshaft is.

[SST4530]

balancer must be one for an external balanced 400 if that is what the crankshaft is.

I 2nd that!

[edvancedengines]

Somehow you need to find out if your Eagle Assembly is Internal or External balanced. It is sold both ways.

The type of balancing also can be changed by the balancing shop that balanced it. If you are running the engine and it has no vibrations then that says that whatever you have is right. If you have a factory 400 balancer the balancer is for an external balanced engine, so you will need the new one to also be for an external balanced engine. The factory 400 balancer had what looks like a notch cut from the outside of it on one side.

iF that is what you have and it has already worked good, the change will be simple, Buy an external balanced balancer and install it. Careful though. Most aftermarket balancers need to be fitted to the crankshaft by internal honing of the balancer. The flexplate should also have a small weight welded to one side of it, if it is external balanced.

If this engine has never run, don't guess at it. Check with Eagle about what it is, if you bought it from Eagle. If you didn't call Eagl;e and ask them how you can tell if the assembly is from them and what to look for if it is internal or externally balanced.

A machine shop that balances can also tell you by weighing the parts and spinning the crank for balancing. Many shops can tell you by just looking at the crank.

Ed