Hi, wondering if someone could help me out.

I recently had my engine rebuilt, and gone through a complete tune up, but when it is running it has a little shake/vibration to it. It is worse in nuetral then in gear and is much more noticeable when I rev it a little. I also noticed that it cranks over longer when starting then it used to.

I have checked everything fuel, air, and spark related that I can think of. I checked the timing as well and it is good.

My question is, could my harmonic balancer be bad, and if it is could the timing mark on the balancer be off making my timing off although it is right at 6 degrees BTDC according to the timing light?

I want to figure this problem out before i damage a rebuilt motor so anything is appreciated. BTW my car is a 91 firebird formula with a 350 TPI speed density and auto trans.

 

the balancer can slip and if it was you would have a bad vibration and your timing if you timed it that way would be retarded

 

Thanks, can this cause any severe engine damage ie: hot valves because of the retarded timing, if i drive it to much this way?

 

It can do damage to the engine bearings. the best way to check it is to pull the crank pulley. the tdc mark is almost straight across from the center hub one of the edges of the center hub. if you do a search for sbc balancers you will see pics of them. sometimes its hard too see a slipped balancer. I have seen real obvious ones as well were the rubber is al mangled and bulging. Didn't see you were from mountain home, I use to do alot of work on the afb

 

My balancer was tweeked and had excess vibration on my 305. Resulted in a spun bearing on cylinder 1.

 

Thanks, I am from mountain home I used to be active duty air force here now I am guard in Boise. Small world

 

What causes a balancer to slip? Is it Removal and reinstallation, age, etc?

 

All of the above.

It's just RUBBER. It deteriorates, tears, gets reefed on during wrenching, and so on. So, ummm, yeah...