Harmonic balancer

[OldChevy61]

In the process of my 350 build and was wondering how does one go about choosing the correct harmonic dampener. There was not one with the block when I got it. Its an 86,87,OEM roller block,1 piece rear main seal.. Looking at summit, I see internal and external balance .

[GM-power]

Depends on what crank your running, if it's internal/external balance from the manufacturer. I'm assuming it's a gm crank, I believe the 1 piece uses a internal balance balancer and a external balance flywheel. If your not sure take the rotating assembly to a machine shop. Might not hurt to have it checked out, and they can let you know what you need.

[storm9c1]

Right, I agree, normally a 1-piece seal stock crank cuts into the counterweight space, so additional balance weight is needed on the flywheel. But front balancer is neutral. On a truck, I'd run a 8".

[Captainfab]

Additionally the timing mark on the balancer will need to correspond with the timing pointer being used.

[storm9c1]

Originally Posted by Captainfab

Additionally the timing mark on the balancer will need to correspond with the timing pointer being used.

Oh yeah I meant to say stock timing tab for a truck corresponds to an 8" balancer. Excellent point! If this engine is of unknown origin, either replace the pointer with a known good one based on the balancer size you need or measure/compare/verify the markings against a known good one.

I also second the advice of taking it to a machine shop. If this is an unknown engine, the right thing to do is balance the whole rotating assembly together as a unit (flywheel, crank, balancer, et al). I know that's not ideal in this case if you are already far along, but that's exactly what's done when the engine is built. That being said, you should be OK with bolting on a new balancer and skipping that step. No need to create more work and spend more money. But if you have a vibration, you will be pulling it back out and doing that anyways...

[OldChevy61]

Thanks guys. I'm a little beyond just grabbing it and running it to town, but I will be headed to the machine shop that done the work on it this morning.