Topic: Engine vibration at RPM
in Forum: C3 Engines
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My stock '74 350 with auto was "balanced" when I rebuilt it. However, at about 5 grand there is a very noticable vibration throughout the car. At the same time I installed safety engine mounts and I wonder if the engine could be twisting enough to put the steel engine mount part against the steel frame support part--thus, the vibration is transmitted to the car frame. It is not a speed problem, but an RPM effect. It is really annoying!
The doghouse has been replaced so maybe the frame is a bit twisted down there. As I recall, changing motor mounts is a hellofva job with the engine in the car. Any ideas on the problem or tips for making the change back to stock mounts easier?
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When was the engine built, and has it had this vibration since then, or is it a "new" problem?
Two things come to mind immediately...harmonic dampener(balancer), and torque converter. Of course, other things can cause it, too, like the fan/fan clutch, or even the belts flopping if they are loose, or "rubbery".
What is this "doghouse" you speak of, and am I in it?
What type of exhaust do you have? If the mounts are a bit mushy, and the engine is tweaking up, the pipes could be rattling against the frame...Adams' Apple 2007-04-14 19:53:36
Two things come to mind immediately...harmonic dampener(balancer), and torque converter. Of course, other things can cause it, too, like the fan/fan clutch, or even the belts flopping if they are loose, or "rubbery".
What is this "doghouse" you speak of, and am I in it?
What type of exhaust do you have? If the mounts are a bit mushy, and the engine is tweaking up, the pipes could be rattling against the frame...
Joel Adams
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The term "doghouse" refers to fenders, hood and front grill unit. Some folks used to jerk them off and make doghouses out of them--not in my part of the country however!
I sorta suspect the harmonic balance because the vibrations were worse before I rebuilt the engine. And the "zero" mark seems a bit out of place when I try to time it. The torque converter was changed at the rebuild. Thanks
in Forum: C3 Engines
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