Harmonic Balancer/Timing Issue

[Dan A.]

For the past several years I have been unable to set the timing on my 69 L-46 with a timing light. The timing marks on the balancer move slowly out of site counter clockwise while the engine is running. I am using a Snap On Digital dial back timing light The car runs well if I set the timing by ear. It also has started making a disconceritng "clanging" noise from the front of the engine when it is turned off. It appears to have some sort of aftermarket balancer. The only thing I can think of is that the ring on the balancer is slipping.

I have had the car 8 years, and it started doing this around 3 years ago. I would appreciate any advice.

[Clem Z.]

Re: Harmonic Balancer/Timing Issue

For the past several years I have been unable to set the timing on my 69 L-46 with a timing light. The timing marks on the balancer move slowly out of site counter clockwise while the engine is running. I am using a Snap On Digital dial back timing light The car runs well if I set the timing by ear. It also has started making a disconceritng "clanging" noise from the front of the engine when it is turned off. It appears to have some sort of aftermarket balancer. The only thing I can think of is that the ring on the balancer is slipping.

I have had the car 8 years, and it started doing this around 3 years ago. I would appreciate any advice.

find TDC of #1 cylinder by removing the plug and using your finger in the plug hole to feel the compression as you bump it over. after finding TDC look to see where the damper TDC mark is located. this will get you close enought to see if the ring has slipped

[Edward J.]

Re: Harmonic Balancer/Timing Issue

Add to Clems post- once you know its on compression stroke, you can use a screwdriver and inset into spark plug hole and use 5/8 socket and rachet and spin the harmonic bal. watching the screwdriver as the piston travel to the top of cylinder. being careful that the driver is not to deep it may wedge it self.

[Dan A.]

Re: Harmonic Balancer/Timing Issue

Update: The ring and the harmonic balancer move independently of each other. I have heard this happens, but have never actually seen it. Now I have.
Thanks for the replies.

[Jeff C.]

Re: Harmonic Balancer/Timing Issue

Has happened to me. Drove me crazy chasing the timing. You need a new harmonic balancer.

[Dennis O.]

Re: Harmonic Balancer/Timing Issue

I've got two original Corvettes; the first is a '67 L-79 with 70K original miles, the second is a 100K '68 300 HP Convertible. Both of these engines were hard to time because the harmonic balancer had slipped and the timing was impossible to set. Trust me, when I had the problem first with the '68, I didn't want to believe what the real problem was. After trying everything else, I finally came to the conclusion that the balancer had slipped; I took it off and sent it to a guy in Portland (he's on the web) who rebuilt the whole front pulley assembly. I got it back, installed it and set the timing perfectly. I am going to take the balancer off of the '67 this fall and send it off. I have found that you can set the timing properly by using a vacuum gauge.

Bottom line as I see it : If you have trouble timing your early Corvette, look first at the harmonic balancer; 40 years is a lot of time for deterioration to take place.

[Terry M.]

Re: Harmonic Balancer/Timing Issue

A good test to determine if the ring (weight) on the damper is moving independent of the hub is to scribe a line between the center hub and the ring. One can also mask a bit and paint a line between the two. Any shift will be visible soon at the scribed of painted line.

DO NOT delay in changing or getting the damper repaired. The ring can come off with catastrophic results. It is not just 40 and 50 year old engines that have this failure. It is common on certain year (sorry I don't know which year(s)) C5 Corvettes.

[John H.]

Re: Harmonic Balancer/Timing Issue

I have found that you can set the timing properly by using a vacuum gauge.

Dennis -

Can you expand a bit on that technique?

[Dennis O.]

Re: Harmonic Balancer/Timing Issue

Disconnect the vacuum advance and make sure the vacuum gauge is hooked up to a good source of manifold vacuum. Advance the timing until you get the maximum reading on the vacuum gauge, and then retard it a bit until the vacuum drops just a little. There are some people on the H.A.M.B. (Hokey Ass message Board - a very popular traditional hot rod board) who say this is superior to using a timing light when working with a modified engine. Worked for me.

[Dan A.]

Re: Harmonic Balancer/Timing Issue

One last question. Any suggestions on a replacement balancer? I have been told the the GM one has been discontinued.

Thanks.

[Dennis O.]

Re: Harmonic Balancer/Timing Issue

I had the one on my '68 rebuilt by a guy who was located in (I believe) Portland Oregon. He did a very good job and it went back on and appeared to be perfect. This engine was rebuilt to stock specs, so I timed it with a timing light and it was right on. They're kinda heavy, so the freight (both ways) isn't cheap, but I believe the whole rebuild was about $80. You should be able to find the guy using Google. If you can't find him, get back to me and I'll dig through my records. Even if you do find him, get back to me because I have to have the one on my '67 done.

[Dennis O.]

Re: Harmonic Balancer/Timing Issue

I found it. It's "dalemfg.com". I see that his prices are up a little, but still in the ballpark. I am very happy with the rebuild on my '68. I've generally found that having an original part such as this rebuilt (if possible), is superior to a new or reproduction part (especially with '67's and the fins vs. no fins issue).

[Dan A.]

Re: Harmonic Balancer/Timing Issue

Thanks - I will give them a call.