The Stovebolt Site Forums The Shop Area Engine Shop Harmonic Balancer Marks Off

Anyone know if the balancer is unique to the engine, were different balancers required? Mine has the TDC notch about 120 degrees off where it should be. Maybe it's been replaced by a PO, or maybe the inner and outter have moved that much.

It's on a '68 250 cid.

Its not likely that it was from another engine. You should start looking for a good replacement or a place to rebuild that one. It has most likely started to move. Is the belt still lined up? It could cause some damage if it comes off, forward its you radiator, rearward and its the timing cover. Is the rubber squished out or soft? Joe

Thanks for the ideas Joe.

The rubber seems solid and I can't move the pulley by hand. It doesn't line up well with the waterpump or alternator pulley. The balancer is somewhat more forward than the other two pulleys. Also the balancer has an extra groove for power steering or something, which is unused on my truck.

Its likely that the outer ring on the damper has slipped. Very common upon old balancers of any make. The rubber gets old, and can't hang onto the outer ring anymore. You'd have to do some research to see if all 250s had their timing mark in the same place, or if the damper could be off of another engine, like a 230 or 292. Is the timing tab integral to timing cover, or is it a bolt-on? On some engine families, its possible to install the timing tab in the wrong location.

If your pulleys don't line up, the problem could be different balancer, wrong accy pulleys, or wrong accy brackets. Is your engine original to your truck?

chip

If it's exactly 120 degrees out you can time it with another cylinder. Straight sixes fire every 120 degrees.

Chip, the timing plate seems to be integral with the timing cover, I don't think its moveable, but I'll have another look. And the engine is likely original to the truck, as all the brackets, the carb, distributor, and casting number put it in the correct year range. It has been out of the truck and repainted and had unknown work done on it. Some of the previous work was of questionable quality. The carb. fitting was stripped, a worn out valve cover gasket was reused with silicone, the list is endless.

Josiah, using the original timing mark doesn't put any cylinder at top dead centre; it's only approximately 120 degrees off. It would be interesting if it did however, as you state, the I-6 fires every 120 degrees.

Fred

I couldn't get my timing marks to line up, either. I couldn't turn the distributor far enough to bring them together, never mind that caused the timing to go way off... I discovered the problem when replacing my front main seal...
Inside the timing chair cover I found a chunk of metal...sort of shaped like a cresent moon, but not concave... it is a "key" that is supposed to lock the balancer to the crankshaft. There is a slot in the end of the shaft and a corresponding slot in the balancer, I think it is called a "keyway", and the key slips in there and puts the balancer and crank in proper relation to each other.
After I put it back together, it was like a miracle! My timing mark hit perfectly on the scale! (I was pretty proud that I had felt out the right timing without the mark!)

good luck...Jerry Mann

I think the 250 has the same diameter balancer as the small block. If so, you can put on a cover. http://www.northernautoparts.com/ProductDetail.cfm?ProductId=56