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HELP, Vibration I cant get around!

Old 02-21-2019, 06:14 PM
3rd Gear Member
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Join Date: Oct 2004
Location: Arizona
Posts: 879
Default HELP, Vibration I cant get around!

hey there, this may be a long story but I am trying to get to the bottom of a vibration that's coming at about 4k RPM I cannot pinpoint.

Here is my current setup
331 stroker SCAT internals
4 speed
28oz flywheel

I replaced the clutch last spring and ever since then I have been having a vibration coming through the car at 4k rpm, in ANY gear. here is is caveat it ONLY happens under load when driving, i can sit in the driveway with clutch in or out and rev it to 6k and nothing, clutch engaged and in gear sitting in driveway... still nothing. while driving in EVERY gear it vibrates at 4k.

I called the shop and they recommended i bring it in and they pulled the trans and we took the flywheel back to the machine shop that balanced and built my motor. it was a few oz off and was re balanced. ok good so far. to be safe we also balanced the tires and had the driveshaft balanced ( which was 3oz off) my speculation at this point would be that it should be 100% better and the issue resolved. we also noticed the crankshaft end play was waaay off at 16 thousandths of total movement ( sue to the vibrations) so we pulled the oil pan and replaced this e as well which are now set at .7 thousandths which is pretty much perfect! ok good. while it was there i had a set of new leaf springs and shocks i decided to install while we were at it. everything should be set and good by now..

got the car back and still.. vibrates at 4k!!! it does however drive waaay smoother from the parts we installed but the vibration still comes in and i am not ready to replace the main bearings again. i am ready to sell this thing its making me so irritated.

the machine shop informed me if we had the original flywheel we could match it and it would be perfect, either way the new one that is balanced is set at 28oz where it should be. im beginning to speculate it may be something else at this point. I do have black widow exhaust installed and those mufflers are LOUD right when the vibration comes in. could this be a cause of this? a misfire? pinyon? trans and motor mounts ?? ( those were replaced but the original 1965 replacement rubber ones)

has anyone experienced anything like this before?
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Old 02-21-2019, 07:40 PM
Gun Jam
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Location: Hills of California
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Does it go away at 4,500 + or does it get worse after 4k?
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Old 02-21-2019, 08:08 PM
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Join Date: Oct 2004
Location: Arizona
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good question, will find out tomorrow when i can take it out. I have been scared to take it past that as it seems as if it gets worse. and afraid of damaging the motor and especially the bearings inside again!
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