After attempting to mock up my siezed '89 denso alternator I had from the 318 I bought 5 years ago (it was seized then) and finding that its hard up against the heads on my 360 with magnum heads. The ~60 amp round back alternator I have just doesn't cut it...its bad at idle. I have the amp gauge bypass completed and I get roughly 11.5v at the dash at low idle with the lights on and the engine running. It gets 14.5 when the engine is above idle, so the car seems to have decent wiring now.

I got to thinking that using a GM 12si alternator might be the hot ticket. They are pretty slim (case without the pulleys and fan is 4.84")



they are cheap and also easy to take apart and rebuild yourself. You can also get tons of these in upgraded versions or even brand new from several sources. I would use the 94 amp unit which has a curve as follows:


Keeping in mind that that's alternator RPM and I'd likely have a 3:1 ratio...so at an 800rpm idle, the alternator would spin at 2400rpm...giving about 64 amps there, enough to run everything in my car and then some. I would also be updating the charging wire from my current 10ga to likely a 6ga with the corresponding fuse link.

So, I'd love to hear your thoughts...even the guys at MAD are recommending this type of alternator. If you're using one on a small block I'd love to see some pictures as well!