I have a 1968 Firebird that I purchased about 2 years ago, the car has the 350 HO with a power glide. The car only has 69,000 documented miles and when I bought the car it had been in dry storage since 1983 when the original female owner passed away. After all the normal things I had to do for a car sitting that long, getting all the leaks took care of etc., the only thing that I did to the engine was pull the oil pan clean it change the oil pump and changed the old plastic or fiberglass or whatever the timing gear Pontiac used back then to a steel double roller and chain. The car runs excellent, no smoke and has good power but it has an engine vibration. The vibration is all the time, it's not real bad but you can feel it in the steering wheel. You can be in park or neutral ease down on accelerator and feel it, when driving at a certain rpm you feel it, I've changed motor mounts and transmission mounts, any ideas would be greatly appreciated.
Since you changed the motor mounts, the next thing to do is hook up a vacuum gauge on the manifold nozzle where your air cleaner hooks into. This will give you a good idea on timing, carb and valves...go from there.
I have a 1968 Firebird that I purchased about 2 years ago, the car has the 350 HO with a power glide. The car only has 69,000 documented miles and when I bought the car it had been in dry storage since 1983 when the original female owner passed away. After all the normal things I had to do for a car sitting that long, getting all the leaks took care of etc., the only thing that I did to the engine was pull the oil pan clean it change the oil pump and changed the old plastic or fiberglass or whatever the timing gear Pontiac used back then to a steel double roller and chain. The car runs excellent, no smoke and has good power but it has an engine vibration. The vibration is all the time, it's not real bad but you can feel it in the steering wheel. You can be in park or neutral ease down on accelerator and feel it, when driving at a certain rpm you feel it, I've changed motor mounts and transmission mounts, any ideas would be greatly appreciated.
Did you pull the engine out to do maintenance?
Can you take a video?
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I did pull the engine to seal all the leaks with engine and transmission but the vibration was there since the first time I started the engine. I didn't drive it much because everything was leaking from sitting 32 years, but I felt the vibration in the steering wheel, not at idle but when you throttle up just sitting with the car in park or neutral you can feel it. I've had people tell me that it's 50 years old that's just the way it was back then, I know better I have a 1969 SS 396 Camaro that I've had for years and it doesn't vibrate, it's not in the drivetrain I'm talking about the car parked with engine running with steady vacuum, not at idle put when you give it a little throttle you feel it and of course driving at a certain rpm you feel it. I know I'm picky I guess put I can't get happy with it. Thinking about pulling engine and trans and starting over.
I've heard some say they had issues like that after they bolted the tq converter up. I don't know if you can unbolt it and spin it to re fasten it in a different spot but you might give that a try. It don't cost nothing to try. I know basically nothing about auto cars. I does sound like it could be a spark miss too( plug, wire).
Put a timing light on your balancer and rev the engine up, does the timing mark move and bounce around? If so, you may have a slipped balancer causing the vibration.
Thanks I'll try that tomorrow we got a pretty good snow this morning and it's like 0 now with the wind chill! I was thinking it might be the harmonic balancer or the torque converter. It's had that vibration from the first time I started the engine.
Thanks for the input, I have replaced all spark plugs and plug wires, I think you might be on to something though about the torque converter. What is puzzling from what the son of the original told me the engine had never been touched except for normal maintenance.
I did pull the engine to seal all the leaks with engine and transmission but the vibration was there since the first time I started the engine. I didn't drive it much because everything was leaking from sitting 32 years, but I felt the vibration in the steering wheel, not at idle but when you throttle up just sitting with the car in park or neutral you can feel it. I've had people tell me that it's 50 years old that's just the way it was back then, I know better I have a 1969 SS 396 Camaro that I've had for years and it doesn't vibrate, it's not in the drivetrain I'm talking about the car parked with engine running with steady vacuum, not at idle put when you give it a little throttle you feel it and of course driving at a certain rpm you feel it. I know I'm picky I guess put I can't get happy with it. Thinking about pulling engine and trans and starting over.
Sounds like your transmission. Either the torque converter or elsewhere. Check vacuum line from engine to tranny to see if it's connected. You have to be careful at installing torque converter so it's pushed all the way in WITHOUT FORCE. You turn it as you push it in.
Did you do minor service to tranny? Change oil/filter on tranny? Was oil burnt? Your tranny could need rebuilding even with a low mileage. It depending on how the car is driven. I doubt yours is that bad but you never know for sure. Does the car shift well? Downshift works?
I agree with you, old cars don't vibrate for no reason. The problem is there somewhere and we will find it.
Your vacuum does not flicker when you alter the rpm's?
I'm so glad I found this forum! I will look closer at the vacuum at different rpm, I'm getting a little older and not as sharp as I used to be! well lets just say not as sharp as I thought I was, I've thought all along it was the torque converter or the harmonic balancer, If something doesn't show up soon I think I'll just pull the engine and tranny and rebuild everything.