Dan, I had this exact procedure done but in reverse. The flex plate's out of balance condition was out of balance matched on the flywheel at a machine shop nearby my home. This shop was the only one that didn't cringe in fear when I mentioned AMC or the procedure. The shop did need the correct donor crank and piston, rod, ring asembly for a guide point. They got a base reading and zero balanced the crank, rod, piston ring assembly then match balanced the flywheel to the flex plate. The engine runs very smooth. They did an excellent job. Any machine shop that knows it's stuff should be able to do this procedure for you. If you don't do at least this much, (it's actually best to rebalance the mating assemblies), your fresh 390 may shake itself apart. Armand > Dan, > Did you have the 390 NEUTRAL BALANCED, or balanced to the stock 390 dampner and 390 Flywheel? This will determine exactly how the Spirit flexplate should be balanced. If you don't know the answer, you could take the 390 Flywheel AND the Spirit flexplate to a reputable shop and they should be able to 'match' the Flexplate balance to the 390 flywheel balance. > > > > > > > > I think I know the answer to this question but need to ask anyway. I have the 390 for the AMX, this has been rebuilt and according to the receipts has been balanced. I'm going to put this into the Spirit as long as the AMX isn't done. Now the question, the AMX is a 4 speed and the Spirit is an automatic. I should just have to take the weights off the flywheel to make it work on the 390, correct? I have a conversion for the 390 to a newer transmission already. > > > > Thanks in advance > > Dan Whitehead > > _________________________________________________________________ > _______________________________________________ AMC-list mailing list AMC-list@xxxxxxxxxxxx http://list.amc-list.com/listinfo.cgi/amc-list-amc-list.com