Rumbly Engine in '89 Civic

I have an 89 Civic LX sedan that needed an alternator and I got a good deal on one from Ebay but it was actually for a '93 civic and is in very good
condition and not a reman. I'm wondering if the fact that it is 70amp alternator and my car only requires a 60amp if it is causing the engine to idle a little lower than normal and possibly overcharging the distributor. It bolted right up of course but the pulley was too big but even the belt used in my civic works well with it because the grooves on the belt line up fine with the 1st 2 grooves on the bigger pulley and the tensnsion is tight enough for it not to flop around. Anyway the engine rumbles a little too much I noticed while at red lights with the car in drive. Does anyone think the bigger alternator could be causing that? Let me know your thoughts.
-jeff
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
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.

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

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
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
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.
-jeff

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Motorsforum.com is a website by car enthusiasts for car enthusiasts. It is not affiliated with any of the car or spare part manufacturers or car dealers discussed here. All logos and trade names are the property of their respective owners.