I've been having problems getting my rebuilt 300 running right. I did a compression test and put a vacuum gauge on it. Compression was in the 140's on all cylinders, vacuum was about 16-17 in. hg. I am between 2,000-2,500 ft. of elevation. The engine has been smoke tested and I have used propane to try and find any vacuum leaks, which there were none. All cylinders are getting spark. New dist., coil, rotor, condensor, points, plugs, cap, timing, dwell and gap have been checked several times. Has new carburetor have checked idle mixture several times. Has new alternator that puts out a steady 14.4 volts. Vibrates the truck in drive, checked the transmission modulator for vacuum leaks as vacuum drops to about 13 in. hg in drive, I've been told this is normal as the engine is under load. The engine has a miss you can here in the exhaust, however if you put your hand on the engine it doesn't seem to vibrate that much. The truck has new motor mounts and transmission mount. What could be causing the vibration? Also, even though the compression test was good pretty much eliminating the possibility of bad rings/valves. Could the engine still have an internal problem such as a flat spot on the camshaft and still get good compression since both valves are closed on the compression stroke? Is there an easy way to check the camshaft without taking it out? Could the machine shop screwed up balancing the crank, thus causing vibration, or would that make the engine throw a rod and thus an impossibility? Finally, The balancer appears to have had a timing mark just painted on it, could the wrong balancer cause noticable vibration?

 

if the cam had a flat spot it would affect the compression. what's the max differance psi differance

 

8 psi , 140 way lowest 148 was highest.

 

I don't think the cam is the problem.Is the damper new?How about the flywheel?

 

Whats the problem, vibration alone or ?

 

New Flywheel, I'm not even sure the dampner is even the right one. It looks like the timing was painted on, could the wrong dampner cause noticable vibration?
Motorhead, yes the main problem is the vibration, the engine does have a slight miss but I can live with that it's the virbration that's bothering me.

 

Are the 240 and 300 dampners the same? I have a 240, I can try swapping the dampner out with. New it looks like there around $200 so that would probably be a last resort if I was sure it was the balancer.

 

the damper isn't balanced, unless it is defective it shouldn't cause vibration.

The flywheel shouldn't be weighted either, if it is, it might be from a v8, i believe the flywheel will fit right up but it is not the correct one.

 

The flywheel should be correct as I bought it new from the parts store. How would a damper go bad? I'm thinking of the right thing right, the weight/pulley on the front of the crank. Someone told me they could slip but I wouldn't have been able to time the engine if it did. Also my steering wheel/column likes to rattle sometimes because of the vibration, is there anything other than the bolt behind the horn and the screws on the dash that I can tighten up?

 

Flywheel doesn't have any weights on it.

 

I'm confused....you're talking about a vibration problem, yet in your original post you say "if you lay your hand on the engine it doesn't seem to vibrate at all".

 

Does it vibrate, in neutral, while parked, rev or idle rpm?

 

Sorry for the confusion, when I put my hand on the valve cover the engine doesn't feel like it's vibrating but now that I think about it, vibration would probably come from the bottom end of the engine.
Motorhead, It doesn't vibrate in park or nuetral. It vibrates in drive or reverse at idle and upon deceleration under abbout 20mph it starts to vibrate again. Runs good while cruising, good acceleration.

 

so did you just slap in this reman motor, and its been vibrating since the get go?

 

Did you rule out the engine mounts?



Good luck