The Stovebolt Site Forums The Shop Area Engine Shop Need More 6 Cylinder Harmonic Balancer Help

I took the sage advice of several members earlier this week and bought a new harmonic balancer for my 250. The good news is I can now time my engine because the mark is in the correct location.

The bad news is that when I drove the balancer on the crankshaft, it hit the timing cover at about the same time that it bottomed on the crank's timing gear (per the Haynes manual instructions). I'm a little scared of this arrangement with no bolt, but I used the puller to back it off enough to clear the cover.

After starting the engine, I noticed that the new balancer wobbles enough to still scrape the timing cover/oil pan lip. The wobble goes away at speed.

Should I pull the balancer a little farther away from the cover, or should I go demand my $95 back?

My brother is a diesel mechanic and his suggestion is to carefully locate the high side of the balancer and then whack it with a big hammer to shift the outer ring on the rubber. I think he's too used to working with very large parts. However it is easier than taking the radiator out again.

Any help would be appreciated.

If I had sold you the balancer, I wouldn't refund your money knowing that you had driven the balancer on instead of pulling it on with a bolt. I had mentioned this in another thread on balancers. You need to drill and thread the crankshaft with a 7/16-20 tap in a hole one inch deep. Get the bolt kit from Summit Racing or whoever, it comes with a heavy washer thick enough not to bend under load.

As far as undoing the damage or returning the balancer, I don't know what to tell you.

Fred,
I appreciate what you said, but I drove the balancer on by striking a large socket held against the hub, just as directed in the manual. I didn't strike the outer ring at anytime. In fact I only had about a 5 or 6 inch swing range, so it was a very slow and orderly process. I would much prefer having a bolt to pull the thing into place (and secure it), but I can't afford the time or money required to yank the crank for machine work right now. I guess I'm limited to the stock method until time and money coincide.

Something I forgot to add about my engine is that it is in a 1973 G10 van where there is almost no clearance between the snout of the crankshaft and the front of the frame. If the drilling of the crankshaft snout is possible with the engine in place, perhaps I need to work on figuring out how to get that front sheet metal and the crosspiece from between the frame rails off. It's had some serious salt over the years, so I'm a little nervous about moving rusty pieces of metal. My last attempt resulted in me replacing almost everything in the front suspension.

By the way Fred, if you're reading. My silly Haynes manual said to drive the balancer on in the manner I described, but your response sent me to the other books I have, and my 1963 chilton's (the first year of the engine series) indicates that the balancer should be drawn on, but it listed some special GM tool.

I'm open to any suggestions and feel kind of sick thinking that I followed published instructions that led me down a path to wasting the price of a dampner.

Marshall,

When driven on, you are striking the center portion of the balancer. The outer portion is held to the inner portion with a vulcanized rubber ring. That outer ring is heavy and has a lot of inertia. When you smack the inner part, you stress the rubber joints between the inner and outer parts of the balancer. If you are lucky, you didn't damage it, but if it wobbles, something is screwed up. Either it isn't straight on the bore or the rubber joint has failed. Drawing it on without a hole in the crank is almost impossible when it is still in the rig.

I had an 80 van with the 250 that I did the same thing you did. If you can get the sheet metal out of the way, or drill a hole in the right place for a long bit do it. I know there are a lot of balancers out there that were hammered on, most of them are luckier than you were. And those vans are rough to work on. As for the bolt size, the new book I got on these engines says to use a 1/2 inch NF bolt. I would get a grade 8. On mine, I made a washer out of 2-1/4" steel bar, cut it about 1/4" thick.

Chevy made millions of these 6's and the older V-8's without a threaded hole hole in the crank snout.Thousands of these pulleys have been hammer driven back with out a problem.It may not be the correct way but its the typical way.The factory I tool i saw is a combo drift and puller.Stll uses hammer impact for installation. I have personally done it a number of times using a heavy hammer and a typical drift with the interchangable heads.Maybe I was luckier.Sixmaniac, something is wrong.The pulley is supposed to bottom out on the timing gear.Maybe you have a V-8 damper? As Fred says, once it maked up by a hammer , you probably can't return it even if the hammer was the prefered method.

[ 01-26-2002: Message edited by: Tony ]

Thanks to All,

Tony, you might be right, but I watched the parts guy pretty closely and we narrowed it down to a damper for a 73 C10 or Suburban 250 which had the same number because the G10 wasn't listed. I have a feeling that light truck 250's are all the same though.

It's an aftermarket damper though, so I wouldn't be surprised if there was a caveat saying a spacer was required between the gear and the balancer that was conveniently missed.

I'm going to pull the balancer till its flush with the end of the snout and see if the wobble goes away. It's currently scrapping the oilpan/frontcover junction and wishful thinking has me believing that maybe the scrape is causing the wobble. If not, I've just learned an expensive lesson.

Thanks again,