The Stovebolt Site Forums The Shop Area Engine Shop Engine vibration? Help!

Have a newly rebuilt 261 in my '56 pickup--3 spd OD w/ 12 bolt posi. Engine was magnafluxed, bored, head shaved, balanced, clutch, flywheel, throw-out bearing balanced as a unit (just pulled cover and rechecked to so if installed according to machine shop markings--yup). Both front and rear seals seem to be leaking since firing it up and experiencing vibraton. Just sent harmonic balancer in for restoration as was not done during rebuild (not back yet).

Symptoms--vibration when engine revved, feel significant vibration when releasing clutch, vibration most noticable at about 50 mph and gets much better at about 60 mph.

Looking for answers. All input appreciated.

does the vibs go away when you press the clutch? Could be clutch plate/pressure plate or drive line to. All the bolts the same in the flywheel? Same length/weight?

Your harmonic balancer is out for restoration ? Is there one on the engine now ?

Was the pressure plate indexed to the flywheel? It should have been if it was balanced.

Have you checked compression and leakdown for a weak cylinder? If you can eliminate differences in power between cylinders, the vibraiton is coming from an out of balance mechanical part. Do you have a balance sheet that shows what everything was balanced to??

chip

No harmonic balancer on engine right now. Rear cover removed. Transmission pulled back. Plan is that when harmonic balancer is returned, install and if problem persists, start isolating parts.

No compression check done yet, no balance sheet was done for engine parts. Have not contacted the machine shop and won't until we know for sure the source of the problem because I'm sure they will ask a bunch of questions if I would call. Timeliness of machine work during rebuild was a major issue and I repeatedly voiced my displeasure over a number of months.

Finally spoke today to the guy who delivered the flywheel/clutch/ etc. to machine shop for balance. He says that they had a h..l of a time and added a bunch of globs to the pressure plate to get it balanced to the flywheel.

The harmonic balancer rebuild will probably solve your problem (or significantly reduce it). Especially if you sent it to a quality builder outfit like Damper Dudes.

Double and triple check your motor mount bolts to make sure they're torqued to specs. May want to check to make sure you didn't drop a weight off your driveshaft.

Just a thought,, how close is the valve adjustment????
AND are you positive the firing order is correct? :confused:
I am not saying it isn`t, but we can all make mistakes or miss things once in a while :o

Checked with Damper Dudes and also Dale Mfg. in Salem, OR. Sent to Dale--20+ yrs of experience. Nice guy.

Thought about drive shaft and even tranny but have vibration while parked. Motor mounts tight.

Valves adjusted and firing order checked.

Really appreciate the help.