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Old 01-27-2004, 11:02 AM
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350 vibration

Hi everyone..I'm new, actually I'm old, 55. Discovered this place while looking for help. Love this stuff. I grew up in the 60's in a small midwestern town full of 55-57 chevs. Drove modern stuff for 30 years but recently bought a 74 El Camino which has become my "second childhood" project. 350 Goodwrench crate engine with 40,000 rounds, basically stock with eldelbrock 600cfm and performer eps manifold, also mallory HEI. I have a harmonic vibration at 2000 rpm, both on the power side and after letting off the pedal. At first I thought it was vacuum and I replaced everything; carb, manifold, distributor, power brake booster, trans vac mod etc. It helped, but didn't cure it. Then I moved on to structural stuff. Motor mounts look good, but I replaced the harmonic balancer and had the driveline balanced with new u-joints. Still there. I did notice that the flywheel has about 1/4 inch of play when it turns, but I hate to pull the tranny if that's not it. Any ideas?
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Old 01-27-2004, 11:06 AM
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any oil leaks
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Old 01-27-2004, 11:07 AM
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i would look to see if your flywheel is cracked.
you shouldnt have any play in your flywheel you dont need to remove the trans to tighten the flywheel i would try to tighten it also
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Old 01-27-2004, 11:08 AM
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It seems to me you've covered all the easy bases. As far as the flywheel wriggle, I've seen worse on new, SFI approved pieces. You may try pulling the balancer and flywheel off and taking them to a shop that balances to have them checked.
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Old 01-27-2004, 11:08 AM
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Not anything serious. I replaced the valve covers with new ones. There are the usual small drips underneath.
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Old 01-27-2004, 11:12 AM
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main bearings checked and oil seals??
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Old 01-27-2004, 12:03 PM
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Sorry, I stepped out for a minute. I have not checked the main seals. You think that would be involved in a vibration?
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Old 01-27-2004, 02:07 PM
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vibration

by all means check that play in the flywheel that don't sound good at all check and see if convertor bolts are tight or if any atr missing
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Old 01-27-2004, 05:50 PM
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This an automatic or manual? ...flexplate or flywheel? IF a manual the flywheel maybe loose, or bad clutch cover. IF automatic, you may have a big block flexplate (externally balanced ...small blocks are internally balanced) or the flexplate maybe cracked or loose also. Good Luck! ...Mark
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Old 01-27-2004, 05:54 PM
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The tranny is a TH 350. Thanks for all the help. I'll give the flywheel another once-over, and go from there. A mechanic friend also suggested the problem could be in the tranny shafts as well??
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Old 01-27-2004, 06:11 PM
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That sounds more like an engine problem. If there was something in the trans, I think it would vibrate at different engine rpms. That 1/4" run-out on the flexplate sounds like the culprit.

I guess I should have also asked if this vibration has always been there or is it a recent event?
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Old 01-27-2004, 06:42 PM
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The vibration is a new thing. It started about 4 months ago. Can't pinpoint anything in particular.
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Old 01-27-2004, 06:51 PM
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Wow, I've never seen a flywheel or flexplate wobble that much. If you put the engine together and know everything is right except you didn't balance the rotating assy then there is a good chance that it's just the harmonics of your rotating assy. If you can live with it leave it but don't spend much time (steady state) at the affected RPM. If you didn't put it together, now would probably be a good time to yank the engine and see what's going on. I had a 74 Jeep pickup I restored few years back. Stockish rebuild mild cam, performer intake, Holley 3310. That thing had a wicked vibration in it but only at 60 MPH on freeway (no tach). 55 or 65 it didn't do it, and I know it was in the engine because I had new custom drive shafts and had replaced all the bearings and seals in the whole drivetrain. I just lived with it and didn't drive 60.
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Old 01-27-2004, 07:19 PM
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caminoguy55,
What year is the crate 350. If it has a one piece seal and you put the old flex plate on the new engine that would be the problem. The newer engines use an external balance where as the older one uses the internal.
Good Luck
Scholman
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Old 01-27-2004, 09:08 PM
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Did you try removing the belts and checking to see if there is any difference. That would eliminate a few things.
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