Rumbly Engine in '89 Civic

I think it could be your engine mounts. The sound guys put in upgraded alternators to power their systems, so that's not likely to cause the engine to rumble.

On a side note, typically the brushes on the alternator go bad, a $30 part from the dealer.

I doubt the extra capacity is a problem, and it won't be overcharging the battery unless it is defective. Look at the belt when the engine is idling, and when you open the throttle a little. If you see the belt "whip" (flop back and forth) more than about 1/2 inch, especially if you see "S" curves flash in front of your eyes, you need to do something about it. Tightening beyond the usual tightness won't help, either. Lord knows I've tried! ;-)

I presume from your description this is a V belt rather than a serpentine belt. Most sizes of V belt come in a premium version (I think Gates calls it "green stripe") that dramatically cuts down on whip. You may have to go to a premium belt, perhaps even a cm or two longer to accomodate the larger diameter pulley. I once had a car that was supposed to take a "green stripe" belt but I could only get a regular belt at the time. The belt whipped so badly it broke in less than a week. By then I could get the green stripe belt and had no more problem.

Mike

It's running fine. The car has been through alot. What's amazing is how interchangable parts are on civics over different years. I think the the extra amps is really not a bad thing anyway. Thanks for everyones advice.