Just got my firebird home today, runs awesome, i love the power. A couple of problems. Timing, and carb issues, there isnt enough fuel getting to the motor, so the timing cant be set quite right untill i change up the carb. I can solve that one, heres my question.

When the car slows down, like at a stop-light, the engine kinda slows down, sucking in the engine vacuum, and puts a real drain on the electrical cuz of the slower speeds. This is with no electrical on, only the brake lights. I was thinking a quick fix would be to get an overdrive? pulley for the alternator.

Basically make it spin faster, and produce more juice. What are concerns i should have when doing this? Will it damage the alt? Overheating the alt? How will affect the battery, and my electrical components? Anything at all.

Second question is, can someone post a picture of how their alternator is mounted (on a carbureted small block)? I know there are two brackets for sure, one is the big arch that goes over the alt, allowing adjustment, the second is the small L shaped one that bolts onto the waterpump and the bottom of the alt, but the previous owner also bolted a THIRD bracket on there. The third one is at the bottom of the alt, at the back, its not a proper one for the car, he just found one and bolted it there cuz he thought it should be one there. So is it supposed to be or not? Because of the custom bracket, the belt is also slightly out of allignment, there is an intermittent squeal once in a while cuz of it. Thanks!

 

An overdrive pully wont work. Yes it will make the Alt spin SLIGHTLY faster, but it will also put more load on the engine, therefor making the RPM's drop even lower than they do now.

I think the correct fix is going to just be to fix it the right way. Your fuel problem is probably whats causing it.

Engines like to idle rich, if you go too lean (or stoich) while idle'ing its going to make the RPM's drop. I had this problem when tuning my Megasquirt, the fix was just to richen up the bins around idle.

 

Ok, first off, have you ever spun an alternator by hand? Doesnt require much to spin the thing, you will lose maybe 1/2 horsepower (if that) by hooking up an alt. A different pulley definately will not change the load significantly. Its pushing around 400 horse, so i dont think thats gonna be a porblem.

HOWEVER, you do have a point, changing the pulley isnt gonna make a significant difference either in terms of power output and i think im gonna have to agree with you on that one.

The car went from a dual 600cfm carb setup (tunnel ram), to a stock rochester, HUGE difference, its very fuel starved. Its parked for the winter, so i think ill pick up a demon or something at a swap meet comes spring, and deal with the fuel prob first, and if the alternator is still iffy, ill get the pulley.

Thanks for the input! I appreciate it.

One more thing, the reason i wanna just swap in a pulley, is because it idles at 1100 RPM, and about 600-800 in D (when its warm). So even at 1100, if you turn on ur parking lights, and interior dash lights, the car will change sound, you can tell there is a power drain (the lights also dim). It shouldnt be happening at 1100rpm, assuming i fix the fuel setup, and get it to idle properly, (around 1k rpms) it will still have the problem. But anyways, like i said, ill start with the fuel.

 

Well alternators take more load to generate more electricity. So if you spin it faster, its going to make more electricity, therefor take slightly more load, thus dropping making your engine speed decrease. Remember, even though you have 350+ CI, you are still making like 30hp at idle.

And yeah, if your lights dim that much even when idle'ing at 1200rpm, i would change the alt.

 

Yea i guess i didnt think of it that way. I just bought the car yesterday, i have all winter to tinker with it. Got a few alts lieing around, will switch em around and see how it behaves. Thanks for the input.