C2 Engine balance

[Randy S.]

I took my 66 300HP 327 into a shop for some work. The mechanic fixed my problem but based on 2 test rides said he felt the engine has an out of balance issue, reving in neutral and when driving.

I have owned the car 10 years and nothing seems out of wack to me. As far as I know the engine is stock but who knows what was done the first 35 years. The mechanic suggested maybe the harmonic balancer but freely admitted that may not be it. He inspected the balancer and noticed cracks in the rubber but no obvious damage.

Any thoughts other than motor mounts or harmonic balancer both of which have not been changed in the 10 years I have owned the car.



Randy

[Edward J.]

Re: C2 Engine balance

Randy, I Had a recent experience with a 63 that had the wrong fan clutch on it, The shaft dia. was not correct on the fan clutch so it would not center on the water pump. and you could see that the fan movement was not correct. It causes quite a vibration. (Just a thought).

I would also check to see at what RPMS the vibration starts when driving car, And then repeat that same RPM with the car sitting , and transmisson in neutral. this will tell you if the vibration is engine or a possible drive line problem.

[Duke W.]

Re: C2 Engine balance

You really need to describe, in detail, why you or your mechanic thinks the engine is "out of balance" - like specific symptoms - to get any useful feedback.

Duke

[Jim T.]

Re: C2 Engine balance

I took my 66 300HP 327 into a shop for some work. The mechanic fixed my problem but based on 2 test rides said he felt the engine has an out of balance issue, reving in neutral and when driving.

I have owned the car 10 years and nothing seems out of wack to me. As far as I know the engine is stock but who knows what was done the first 35 years. The mechanic suggested maybe the harmonic balancer but freely admitted that may not be it. He inspected the balancer and noticed cracks in the rubber but no obvious damage.

Any thoughts other than motor mounts or harmonic balancer both of which have not been changed in the 10 years I have owned the car.



Randy

Randy the motor mounts and harmonic balancer are still the originals on my original owner 68 327/350 and it still runs great. What did the mechanic repair that required two test rides? Were you with him on the test rides?

[Randy S.]

Re: C2 Engine balance

Jim,

I work for an import car dealership. One of our senior mechanics goes back to day when we had Oldsmobile and cars had points and no OBD ports. I thought I had an ignition miss and recently replaced plugs to no avail. He said bring it in and he would find our old ignition analyzer and check it out.
I told him to test drive for the ignition miss.

He found nothing wrong with the ignition system after putting it on the analyzer but did adjust the stock Holly and found a small vacuum leak at the STV valve.

Car runs great now. However, I removed the ignition shielding to facilitate him checking the ignition system so the verdict is still out on that miss until I replace the ignition shielding and test drive.

Concerning the engine balance he said it doesnt seem to rev as smoothly as he thinks it should. Very subjective and hard to be specific as Duke as noted. I am sure this is his honest opinion as he is not trying to sell me any additional work. I do not have a vibration at a specific RPM range or shifter "buzz". If it is an internal balance issue from a previous rebuild I will have to live with that.

I am not going to worry about it. I am going to take the belts off and see it feels any different ( alternator and fan clutch) and motor on.

Re the harmonic balancer is there a check to see if it is defective? if the outer ring has slipped slightly obviously my initial timing is off but how would the engine behave? Should I expect a vibration?

Randy

[Clem Z.]

Re: C2 Engine balance

if the clutch was replaced without balancing it could cause the problem.

[Bill M.]

Re: C2 Engine balance

Re the harmonic balancer is there a check to see if it is defective? if the outer ring has slipped slightly obviously my initial timing is off but how would the engine behave? Should I expect a vibration?

The timing mark should line up with the keyway for the crank.