Topic: 72 mustang engine swap help!!!

[dwolf2002]

ok, i have a 72 mustang with factory short block 302. went and bought a like new long block 1986 5.0 ho motor that can out of a police interceptor car. the 86 motor was throttle body and i converted it to carb by taking the stuff off of my 72 and putting it on the 86 motor. the motor runs great but the problem is that the car has a bad vibration now and its coming from the motor. i used the fly wheel and starter from the 72 and the heronic balancer also but it seems like its out of balance (the car vibrates like the sound of a bad u joint) which seems it was the fly wheel. so i pulled the tranny agian and looked and the 86 flywheel is like 14 1/2 inch and the 72 is 13 1/2 inch so i couldnt put the 86 flywheel back on because it wouldnt fit in the bell housing so can anybody give me any info on how to fix this problem or tell me what the problem is. thanks

[Soaring]

That 72 is a 28 balance, and the 86 is 50 oz.  Therein lies your problem.