is this motor stock or has it ever been rebuilt? if it has been rebuilt and was balanced then there is a chance that the harmonic balancer had the weight changed on it. also you could have chucked a weight off of the flex plate or fly wheel. once and only once i had a guy who had just rebuilt his motor and had a vibration. it had a cracked cylinder wall that he had missed and that was causing his vibration. i would do a compression test and a cylinder leak down test to see if all cylinders are working in the same conditions or if one has a problem.
The guy I bought it from said it and the tranny only had 5000 miles on them. Ive replaced wires, plugs, harmonic balance, motor mount and tranny mount. The mounts didn't look new when I replaced them so if he did rebuild it he didn't replace either mounts on the engine or trans. There's a local guy with a mid 80's 5.0 and aod trans for sale that I'm interested in. It's EFI so I was wondering if my intake and carb would work, or if it would be worth the trouble. any suggestion would be appreciated.
Yes, your intake and carb will work but, IF YOU GO AHEAD, you'll want to read this http://mmb.maverick.to/showthread.php?t=36034 to see all the issues and answers on the swap. Since you have a non-roller 302 you have the parts to make the swap. See also the threads on AOD swap if you haven't already. There are a lot of issues to work out if you go for it. I wouldn't go that route till I knew what the problem with the current engine is. A shake from a miss fire will be less noticeable at higher RPMs. A shake from an imbalance will get worse with higher RPMs. ARe you sure which you have?
I know that I have a misfire, I can here it. It vibrates more in gear stopped than it does idling in park, but when I race the engine slowly the higher rpm's seem to cause more vibration than the lower rpm's.
an exhaust leak can sound just like a spark jumping from a plug. or can you hear your missfire in the tail pipe? as said earlier if the vibration gets worse as you rev the motor higher you most likely have a balance problem with the motor.
I burnt an exhaust valve in my '73 (original engine, ~70k miles). I took a piece of paper, and held it to the tail pipe (on the correct side, I had duals, no x/h-pipe). The paper would suck back against the tail pipe every few seconds at idle. That is how someone told me to check. A compression and leak down test verified it later. I think those test are your best bet.
Vibration update: Well in my search for the vibration problem I found out that the motor is not a 72 302, it's an 85 HO. I've been buying 72 parts and everything so far has worked but, the harmonic balance I bought was a 28oz not the 50oz that's required. I have since replace with a 50oz and the vibration throughout the rpm range seems to have moved to just the low rpm range. Checked the flex plate and it is a 50oz, looks new. Any idea where to go from here? Things done are: plugs, wires, motor mounts, tranny mount, harmonic balance. Oh yea, other than the vibration this thing runs like a scalded dog!
I have a similar problem with my mav, it vibrates constantly, but the vibration is cyclical, meaning it comes and goes every few seconds, like 1-2-RRRRRRR-1-2. The engine has very few miles since serviced, all valves are in perfect condition, so are the pistons and rings, cables are new, so the spark plugs. Checked timing, is fine. Could it be the harmonic balancer? Could this vibration cause future problems in the engine? HELP!!!
