Big-block harmonic balancer

[Wayne L.]

I can only get the harmonic balancer to go on the crank about half way. Still have an inch or so to go, and it just will not go on any farther. The engine is a 1967 390hp, and I'm using the 7" dia. balancer 3860008. Can someone tell me what the interference fit is supposed to be? Is the bore in the balancer tapered or straight? This balancer came from a 1968 390 hp engine. Is there a difference in the bore or crank snout diameter between 1967 and 1968?
Thanks, Wayne

[Mark #28455]

1968 and 1967 dampers are same

You should be using an installation tool, not just pulling it on with the center bolt. If you use the bolt method, you can booger up the threads and it won't go on. There may also be a burr on the crank where the Woodruff keys fit into the crank snout - this can cause it to hang up. Also if a hot rodder used an offset key for the timing chain, it will hang up. Usually a used damper has the correct interference fit from the factory, but I have seen a couple new ones that were too tight and had to be honed a touch.

Make sure you're using sealer on the keyway or you'll be back. In addition, are you using some oil on the crank snout? If dry, you may gall it.
Mark

[Wayne L.]

Re: 1968 and 1967 dampers are same

Mark, thanks. I was using an installation tool, but it "galled-up". I was over 150# on my torque wrench! I can't see any burrs, and had oil on crank snout. Timing chain and sprockets are bone stock. Thanks for the tip on using sealer on the keyway. There seems to be .010-.015" interference, that is, the bore of the balancer is .010-.015" smaller than the diameter of the crank. I will check again for burrs, and then get out my hone. Thanks again, Wayne

[Joe R.]

Re: Big-block harmonic balancer

Hi Wayne:

I don't know about the big blocks, but on my 67 327/300, with the balancer fully installed, the face of the balancer protrudes almost exactly one inch out beyond the end of the crankshaft. So, when you say that you still have about an inch to go, make sure you are looking at a valid reference point.

My guess is that that this is not your problem, but I thought I would mention it just in case.

If you have a set of dial calipers with a depth guage on the end, with the balancer off you can measure the distance from the end of the crank to the face of the timing gear on the crank, and then measure the depth of the balancer. The difference is the depth of the crank from the face of the balancer when the balancer is fully seated. If you are having to fight hard to fully seat the balancer, this dimension will help you confirm that the balancer is all the way on.