Harmonic balancer was the problem!
Thread Starter
Cruising
Joined: Sep 2007
Posts: 10
Likes: 0
From: Raleigh NC
Harmonic balancer was the problem!
I wanted to let those know that may be chasing a vibration or perceived "miss" in their engines what I found with mine. I have been trying for several months to find the root cause of why the L98 engine in my '91 would not run smoothly. While I did find some bad injectors, worn plugs, a bad EGR valve, filthy intake plenum, etc., the motor still ran rough. I finally had a Chevy mechanic tell me it felt like a vibration rather than a miss. I changed the harmonic balancer and that cured the problem.
The old balancer looked OK on the car but its hard to see it clearly. Once I had it off it was very obvious that it was about to come apart. I have photos but cannot post them for some reason. This was an obscure and apparently uncommon issue. I talked to many mechanics and only one said that may be the problem.
The old balancer looked OK on the car but its hard to see it clearly. Once I had it off it was very obvious that it was about to come apart. I have photos but cannot post them for some reason. This was an obscure and apparently uncommon issue. I talked to many mechanics and only one said that may be the problem.
Race Director
Joined: Dec 2000
Posts: 17,551
Likes: 26
From: El Paso Texas
Good post....and at least you caught it before it came apart. I wasn't so lucky. Same problem on my 84, a vibration I couldn't track down. The balancer came apart suddenly and took out the oil seal on the timing cover. On the upside, I figured it was a good time to change the timing chain as well.
It's amazing just how much effect they have on how the engine runs, and that they can cause this serious of a balance issue without having any outward symptoms.
Good catch.
It's amazing just how much effect they have on how the engine runs, and that they can cause this serious of a balance issue without having any outward symptoms.
Good catch.
Melting Slicks
Joined: May 2007
Posts: 2,382
Likes: 2
From: Kathleen FL
I might have that same issue on my 88. There seems to be a cyclic vibration which could either be a torque converter issue or just the harmonic balancer as you saw it. Right now its all taken apart and heads are about to come off so I may as well tear into it further while I can. But thanks for the heads up.
