Alternator Underdrive Pulley

[DAVID GAGNARD]

After expirementing with under drive pulleys for about a year on three different vehicles (street car,p/u truck,race car) and talking to 2 different manufacters of pulleys,I have found out you DO NOT need under drive pulleys and SHOULD NOT use under drive pulleys on anything but a race car NOT used on the street...........

On a street driven vehicle I have found the crank pulley should NOT be anymore than 1 inch diameter smaller than the water pump pulley..........By going to under drive pulleys,you MAY save 5 to 10 hp tops,not worth it for the overheating/charging problems...........I used under drive pulleys on my street 65 Fastback for a year and was always watching the water temp gauge in traffic,not worth the headache!!!!!!!!!!!!!! Now,my crank pulley is exactly one inch diameter smaller than my water pump pulley and I can drive the Forth of July parade with my daughter in 100 degree heat for 45 to 60 minutes,the first 45 minutes the temp stays on 180 (180 thermostat),after 45 minutes of idling it slowly climbs and after another 15 minutes or so it is all the way up to 190,which I can live with,can't remember the last time it was past 195...............

Under drive pulleys are NOT WORTH the few hp you save for a street driven vehicle,even the March people will recommend only use them on full blown race cars!!!!!!!!!!!!!!!!

David