Engine Vibration - 3K RPM

[SSL]

I'm having a engine vibration at 3000 RPM and haven't been able to diagnose the problem. After about 300 miles of use, the vibration started and seems to be engine related.

Drivetrain Details:
- ZZ502, Fluidamper, Holley 850, MSD Digital6, March serpentine with AC
- T-56, Centerforce DF, Scattershield (indexed)
- Hydroboost brakes

Items looked at so far:
- Vibration occurs when:
- Moving and sitting still
- Clutch engaged or disengaged
- Trans in gear and out of gear

- Plugs and wires checked - plugs clean, gap correct
- Replaced waterpump

Any ideas on what to look at next?

Thanks,
Steve

[deuce_454]

my guess would be that you have an internal engine un-ballance that exites the engine in a resonant frequency at the stated rpm... the time delay could be from a failed engine mount thet took 300 miles to surcome to the beating at 3000 rpm...

the diagnostic fix is to replace the engine mounts.. and the long term one is to remove the engine and have the entire rotating assembly (including flywheel and clutch) dynamically ballanced... (if you arent running an incorectly ballanced damper or flywheel in the first place... they could be labeled wrong, or somone have given you an internal ballanced when you needed external or vice cersa)

my 2 cents

[deuce_454]

and wellcome by the way.. dont forget to introduce yourself...

[Smittys67]

Look at the flywheel bolts or harmonic balancer or pulleys.

[comp-spec]

If you know for sure there was no vibration before check the balancer and flywheel

[68TINCAN]

If The Vibration You Feel Is Above 3000 Rpm With Car Sitting Still, You Can Safely Say It Engine Related. But Before You Tear The Engine Apart, I Would Look At The Basics. Timing, Air Fuel Mixture And The Msd Unit Itself. I Would Take Out The Msd Unit To See If That Helps. Also, If You Have A Fan Clutch, It Can Cause A Vibration If It Is Locked Up.

[copo69]

by chance are you running a center force clutch and pressure plate. if so when you installed it if you bent one or more of them forks with the lil square weights on it you will get a vibration also. this happened to a friend of mine and he spent lots of money trying to solve the problem.

[SSL]

Finally figured out the problem...

Bent alternator shaft. Took the belts off and all is well. I'm relieved that it's not internal engine or trans related. Thanks for all who pitched in to help!

Steve

[deuce_454]

congrats... i didnt think of that one