KJL

I jsut installed Spal dual electric fans. I also install an under-drive pully set. I Went for a ride and killed the battery. At idle I believe with under drive pullies the alt does not charge. I also noticed that before I even put the fans and pully set on at night when I would rev the engine the lights would get brighter. Would a higher amp rated alt help? I am also going to put the stock pully back on the alt. :(

Dwayne 76

Looking at your profile I noticed that you have a '72. I'll have to wait 'till I get home to answer that question. I have a '76, but I think we have the same alternator.

Eddie 70

I don't think the alt. pulley is the culprit, at least not on my underdrive set. The actual underdrive comes from the crankshaft pulley. It is smaller than the stock pulley, slowing all accessories down. Still if you were driving, the fans should not have downed your battery. Are the fans still running when you shut your car down. This might cause the dead battery

KJL

The fans are wired to shut off when the car is off. And they do. The under drive pully set I have came with an alt pully that is a bit bigger in diameter than stock, I figure the stock pully will pick up the rpm a bit. I guess there is also the chance that my battery is the problem. I was told that if your headlights get bright when you rev the car there may be a problem with the voltage regulator. I brought it to NAPA to be checked and they said it was ok.

BTW I can really feel an improvement in lower in torgue since I installed the fans with the underdrive pullies and the 1" spacer under the carb. I also installed the Edlelbrock Fuel/air monitor and it shows I am running to rich. Once I get it all dialed in its back to the dyno to see If pulled the numbers up.

I am currently at 233hp and 311 tq sae corrected.

LAvetteman

The underdrive pulleys are not helping, but your main problem is probably your alt being too small. I believe a stock C-3 alternator puts out 60-80 amps max. How much do your fans draw. Cutting it off when not needed will help a bit.

I believe the stock alternator for a C4(dual fans) is around 120 amp.

Wish you were closer, I have a D.C. amp meter you just lay on top of the wire you want to measure current from, that would tell the tale.


[Modified by LAvetteman, 12:29 PM 8/18/2003]

AlwaysWave

I think a stock 72 L48 alternator was 42 amp.

I also have the Spal fans. I installed a PowerHouse 110 amp alternator when I did the fans.

vettemack

The amperage rating is stamped on the alternator by the part number. If you have AC, it is probably 61 Amps. If not, then 42A.

KJL

Thanks for the replies, I just purchased a 100 amp alt and Ultima battery from Summit.

Alwyn678

:seeya Keith that should do the trick.......Good luck