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Sep 16, 2000
New Hampshire
1990 Corvette ZR-1
I got the ZR back on the road. The alternator was bad as I had presumed. It is possible, as the service manual suggests, to replace the alternator without having to remove the plenum. However, you do have to remove the throttle body and the key to being able to get the alternator out of there is removing the oil pressure sending unit. Once you remove that, you're set. I will still post pictures showing what the underneath of the plenum looks like. Time to go rip up some pavement and :drink !!
Good deal Rob. Glad you got that taken care of. Mine goes up on the lift tomorrow morning to tighten up the oil pan bolts..........
I was rippin' up some asphalt earlier today:D

Rob and I talked by phone Friday night about his alternator change-out and emailed this morning about it.

An important point came up in our email exchange and that is when you buy an ACDelco Reman alternator or any remanufactured (rather than rebuilt) alternator, sometimes the output current stamped on the alternator end frame will be incorrect. Initialy, this caused Rob some concern and that was the subject of our conversations. In the end, Rob's dealer explained the situation and confirmed he had the correct alternator.

In Rob's case, the ACD Reman PN 321-567 was the correct unit for an LT5, however, the endframe was stamped "108A" which, ordinarily, would indicate it was the *wrong* unit for an LT5 which takes a 120 or 124 amp alternator.

In the end, the 321-567 is the right reman part regardless of what the endframe is stamped because the remanufacturing process mixes parts. It's the internals that make a CS144 put out 120 amps not the endframe. ACD and other remanufacturers may not take care put the correct endframes on a reman assy. so going by the endframe stampings as to output of a reman unit is not a good idea. It's the remanufacturer's part label that's the difinitive ID.
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Thanks Hib. I should have mentioned this in my initial post but was late for a Corvette show down in Manassas, VA and didn't have much time to post.

What was confusing, as Hib mentioned was that behind the pulley is a series of numbers. On the upper right hand corner, is the output. The unit I took out of the car said 120A indicating 120 amps. The unit I purchased said 108A even though the part number and unit number on the box was correct and the silver and black ACDelco label on the alternator itself yielded the correct numbers.

All in all...it was a good experience. I got to blow $225 in tools just to do the work. I couldn't resist the really cool multimeter (didn't have one) and let me tell ya.....serpentine belt tool - Sears....the best $39.00 I ever spent!!!! And of course, it's always good to be right in the middle of a job when you realize, you're missing your 10MM socket and 1/2 the bolts on an LT5 engine are 10MM. It's even more of a joy when you unplug that coolant hose that runs on the right side of the plenum and goes into the throttle body....plug it....prop it up so it doesn't leak, run out to Sears to get that 10MM socket and come back to find that your prop slipped and a stream of coolant is coming from under the rear center of the car. Hib was on the phone with me at the point I opened the door....I think my words were something like....."what the $%^& is that!?" I had to mop the garage floor this afternoon after I pulled the car out. The funny part about it is that a neighbor walked by and stopped in who I had never met before. He started off with...."do you mind if I ask you a car question, since you seem to like...be all into cars and stuff." I looked down at the giant wet spot coming from underneath the car thinking...."if I was you buddy....I wouldn't be asking me a car question." :D

In any case, I finished the job at 4:00 this afternoon. The Vette is not only thankful...but so is my lower back....the front tires make awesome seats when necessary, but still doesn't take the strain off the back. :)
Rob said:
...the front tires make awesome seats when necessary, but still doesn't take the strain off the back. :)

Boy do I agree with you on that! It's nice to have the clam shell hood in that you can reach things a little easier, but the reach is the thing; after extending yourself like that for so long, it's gonna hurt.

:upthumbs Congrats on a job well done, and I hope you were able to help your neighbor with his questions. ;)

Thanks for the helpful insight on the alternator Hib and Rob. Boy, I can't wait to do mine now.


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