I run a stock alt pulley, 10%ud crank pulley and spin mine to 7400 all the time with no voltage loss.
I also did the same thing with the stock crank pulley with no issues.

 

I think that a good tune would have masked the fact that my alternator was quitting at high rpm. It showed up when I had my 60 lb injectors with incomplete data. I think that the injector voltage offset being incomplete or false at high rpm caused my truck to go lean when the alternator shut off at high rpm. I would not have known that my rebuilt alternator was bouncing the brushes at high rpm if the lean condition wasn't forcing me to find its cause. It never happened again after I bought a new alternator, and now I also have new injectors with good data.
You guys are lucky to have no such issues.

 

I wish I would have seen this sooner. Are you still having issues?

I feel like I had more alternator issues than anyone and it made me start this thread several years back https://ls1tech.com/forums/generatio...failure-s.html

It's 50 pages long with some decent info but probably not much to help your exact situation.

From my experience spinning these alternators high you are not losing voltage from RPM... well you may be, but because of the alternator being a POS or the belt slipping, you do not need to slow the alternator down.

I ran the stock alternator in my camaro to 6900 rpm daily and the 145 amp truck alternator. I also ran the stock 105 amp and a stock 145 amp alternator to 6500 daily for years in my 2004 Sierra.

EVERY SINGLE alternator I bought off the shelf at a parts store went to **** the first time it saw some RPM. Usually anything over 6k immediately killed them. That's if they even made it that far. Most just went to **** period without any abuse. That all stopped the second I went to an OEM alternator. And it worked for tons of other people too. AC Delco is a brand that GM uses, but I bet the off the shelf AC Delco is different than the OEM alternator. I tried rebuilt and new in every brand I could from 4 different suppliers. NONE worked for long. The ones that lasted longer than a couple of weeks died the second they saw some good RPM.

That's why I started using used 145 amp alternators and created that thread. It helped and cured tons of peoples problems. The reason I chose to go used was to get an OEM alternator. There is no other alternator built to that level of quality except other $500 alternators and I wanted to test a theory, before testing it on a $500 alternator (OEM new I believe are over $400) in case it wasn't the alternator causing the problems. So I thought how do I get a $500 OEM alternator cheap... go used. And the used alternator fixed every issue I had. It also pulled the belt a little tighter and stopped the belt slip I was having, and throwing the belt.

Around that time, it's been so long, I also did a buick high wall tensioner pulley that ended up being a hair larger in diameter than the stock pulley, that also increased the pressure my tensioner put on the belt and helped/stopped the slipping and belt tossing.

Used alternators are around $50, it's worth a shot. Or get a brand new one from GM.

I had a 2004 GMC sierra like I said with a sound system that pulled over 100 amps and I had electric OE fans that pulled around 40 amps. The only time I ever saw a loss of charging with that was when everything was at FULL TILT and at idle. You should have enough alternator with the 145 to do what you're doing and not have charging issues.

 

I actually havent figured out if I have fixed the issue. I parked the truck for the winter right after the last track runs of the year. I have a new AC Delco 145amp alternator, wiring upgrade and I also sent in my meth pump to be checked out. I figure I can check it out some time around april or May when the roads are dry again.

Been stupid busy trying to fix everything up here from the damn Earthquake. Pretty much all my truck funds went into a new shop floor that cracked and moved around. LOL. My insurance deductible for earthquake damage was $60k. Pretty much for catastrophic failure only.

I will revisit this post this coming spring. Thanks for your info. It is much appreciated.

 

Man that sucks to hear, that's a hard hit. Looks like the good news is you didn't get taken out by the earthquake too.

Good luck with it and update when you can, if I can help any further let me know.