Alternator Size
 

Hey fellas,

I have 90 amp alternator on my SBC 350 with HEI, Vintage Air, FiTech EFI & Pump, 17" Electric Fan, and radio and I am having a lot of issues with the truck just staying running.

I am thinking about going to a bigger alternator. What amp should I go to?

Thanks!

Re: Alternator Size
 

Do you know the total amps your pulling at any one time in a normal day? That is, have you added the amps up on the above listed items?

Re: Alternator Size
 

If you don't get an answer here I can see about moving this to the Electrical section - http://67-72chevytrucks.com/vboard/f...splay.php?f=64

Re: Alternator Size
 

I run a Mechman in Dodge 370 amp. They have a 170 with V belt or rib. Custom ones can be made to order
https://www.mechman.com/alternators/...let/1963-1985/

Re: Alternator Size
 

Re: Alternator Size
 

Might want to measure the voltage at several places such as battery, fans and alt.

Re: Alternator Size
 

Pirate:
Few of questions:

* What size pulley are you running on crank? Performance (i.e. smaller) crank pulley results in alternator turning slower and water pump running slower. Causes problems for street car with cooling and charging.
* Is cooling fan running continuously or only when engine exceeds temp? Running it all the time needlessly taxes charging system.
* What is battery voltage when engine is running?

Short answer is 90 amp alternator is unlikely to be the source of your problem.

Hope this helps.
Regards
Steve

Re: Alternator Size
 

I agree, I doubt it's your alternator.
Take your belt off and see if it runs any better off the battery.
Motor will not cool, i.e no fans or water pump.
However, running a short time on a fully charged battery should not hurt anything and it may eliminate the alternator as the source of your problem.

Re: Alternator Size
 

I agree with vn63, you’re running a bit of a load, fuel oump, ac, etc, personally I use minimum off 100 amp with less than that…the difference in cost for a bigger/better alternator is minimal…think of it this way, a 6 cylinder will move your vehicle, and use more fuel because it works harder doing the same thing as a properly tuned v-8….