The fix for my endless alternator failure's
WOW... put that junkyard alt on and there's a steady 14 volts all the way to 5k!
Just to be safe, I want to put a 3.5" alternator pulley on but haven't found one yet. I think that would help make them last longer.
Anyone know where to get one?
Edit: https://www.summitracing.com/parts/krs-krc40150600 should work. With the stock 2.2" pulley, at 1000rpm I've got 3200 alt rpm. with a 3.5" pulley I'll have 2071 alt rpm.
Just to be safe, I want to put a 3.5" alternator pulley on but haven't found one yet. I think that would help make them last longer.
Anyone know where to get one?
Edit: https://www.summitracing.com/parts/krs-krc40150600 should work. With the stock 2.2" pulley, at 1000rpm I've got 3200 alt rpm. with a 3.5" pulley I'll have 2071 alt rpm.
Last edited by 89ROC-Z; Sep 15, 2017 at 09:40 PM.
I'm going to bring my old alternator to the local shop and pick their brain on it. He said that the diodes could be bad, and he might be able to put different parts inside to make it live.
Will update with what he finds out!
Will update with what he finds out!
WOW... put that junkyard alt on and there's a steady 14 volts all the way to 5k!
Just to be safe, I want to put a 3.5" alternator pulley on but haven't found one yet. I think that would help make them last longer.
Anyone know where to get one?
Edit: https://www.summitracing.com/parts/krs-krc40150600 should work. With the stock 2.2" pulley, at 1000rpm I've got 3200 alt rpm. with a 3.5" pulley I'll have 2071 alt rpm.
Just to be safe, I want to put a 3.5" alternator pulley on but haven't found one yet. I think that would help make them last longer.
Anyone know where to get one?
Edit: https://www.summitracing.com/parts/krs-krc40150600 should work. With the stock 2.2" pulley, at 1000rpm I've got 3200 alt rpm. with a 3.5" pulley I'll have 2071 alt rpm.
Be interested to see what the builder says, hopefully he can source some quality internals for it. That seems to be the issue with the remans, they use low quality diodes etc.
TECH Senior Member
Joined: Jun 2016
Posts: 22,303
Likes: 3,619
From: Central Cal.
And I bet near 100% of the remans just have new bearings and diodes, the ones that just got new bearings only are the few that survive is my guess. I highly doubt the remans are getting fresh windings or complete armatures. So the "new" ones use new armatures and all but still fail in the same pattern failure manner. So the common denominator here is diodes. Unless i'm forgetting a component in my haste to leave work.
TECH Senior Member
Joined: Jun 2016
Posts: 22,303
Likes: 3,619
From: Central Cal.
And I bet near 100% of the remans just have new bearings and diodes, the ones that just got new bearings only are the few that survive is my guess. I highly doubt the remans are getting fresh windings or complete armatures. So the "new" ones use new armatures and all but still fail in the same pattern failure manner. So the common denominator here is diodes. Unless i'm forgetting a component in my haste to leave work.
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Verdad Gallardo If you're not running an overdrive crank pulley leave the alternator pulley alone. I spun mine to 6800 rpm daily for a long time and the two owners after me of my car did too with 0 alternator issues (this was over a period of roughly 4 years and roughly 40 thousand miles until the car was totalled, the car went all over the country and got raced a lot too). Others that have used the used truck alternator haven't reported any failures either so no need to fix what ain't broke on this one. And if you use the larger pulley you'll likely start having charging issues at idle and create problems you didn't already have.
Be interested to see what the builder says, hopefully he can source some quality internals for it. That seems to be the issue with the remans, they use low quality diodes etc.
Be interested to see what the builder says, hopefully he can source some quality internals for it. That seems to be the issue with the remans, they use low quality diodes etc.
Didn't get to the electric shop today, but will update with what re recommends!
I have the stock 7.2" crank pulley. I believe the alt will spin around 20k in this form. With the oversized alt pulley it should be 16k. You're confident the junkyard kg3 handles that kind of rpm without issue?
Didn't get to the electric shop today, but will update with what re recommends!
Didn't get to the electric shop today, but will update with what re recommends!
If all of your other alternators handled those pulley sizes, why wouldn't this one?
I also spin my truck up to 6500 rpm damn near every day of the week for the past few years with a kg3 on it. The camaro saw 6800 rpm daily for years. So that's all I got as for being sure.
TECH Senior Member
Joined: Jun 2016
Posts: 22,303
Likes: 3,619
From: Central Cal.
Alternator life at high RPM comes down to two things; balance and GOOD bearings. Armatures by nature should be very well-balanced IF free of crud, so that narrows it to GOOD bearings. I don't know if truck alternators are made with any better bearings than the auto ones, but they do seem to hold their own at speed.
I finally went with the 3.5" alternator pulley along with my "truck" alternator. I killed every new truck alternator after taking it up to 7000rpms with the stock size balancer and like the above poster mentioned, its too much rpm for the alternator. Granted these were new units and not pull offs from used trucks but they were the large case 145amp units. I guess some people are just luckier than others. I have killed 3 Fbody alternators and 3 truck alternators ever since i took off the under drive balancer and i dont think its a coincidence that the new ratio of alternator to engine rpm is the issue... If anyone still has high rpm issues with the truck alternator I would at least consider an under drive balancer or a large alternator pulley.
My idle RPM is 1000 and have full charge at idle.
My idle RPM is 1000 and have full charge at idle.
I finally went with the 3.5" alternator pulley along with my "truck" alternator. I killed every new truck alternator after taking it up to 7000rpms with the stock size balancer and like the above poster mentioned, its too much rpm for the alternator. Granted these were new units and not pull offs from used trucks but they were the large case 145amp units. I guess some people are just luckier than others. I have killed 3 Fbody alternators and 3 truck alternators ever since i took off the under drive balancer and i dont think its a coincidence that the new ratio of alternator to engine rpm is the issue... If anyone still has high rpm issues with the truck alternator I would at least consider an under drive balancer or a large alternator pulley.
My idle RPM is 1000 and have full charge at idle.
My idle RPM is 1000 and have full charge at idle.
If you had used the used alternator you wouldn't have had to swap pulleys.
So it's not really that it's too much RPM for the alternator, it's too much RPM for the crap alternator, the good ones (used OEM) take it.
Teching In
Joined: Aug 2012
Posts: 5
Likes: 0
From: tx
Just ended up buying a prostart alternator 102 amp. It has Delphi engraved on it. So hopefully it's a good 1. So far so good. Voltage with car on, ac, lights, and radio showing 14.2 volts when I tested it with my multimeter. I don't know how people are swapping these in 15 mins or so. People must have spaghetti arms and fingers. After cleaning my grounds and installation of the alternator it took me 2 hours. Definitely a pita. This alternator better last 10 years.
Last edited by the crowing; Oct 8, 2017 at 08:51 PM.
Just ended up buying a prostart alternator 102v. It has Delphi engraved on it. So hopefully it's a good 1. So far so good. Voltage with car on, ac, lights, and radio showing 14.2 volts when I tested it with my multimeter. I don't know how people are swapping these in 15 mins or so. People must have spaghetti arms and fingers. After cleaning my grounds and installation of the alternator it took me 2 hours. Definitely a pita. This alternator better last 10 years.
Hope it works out for you, I have no idea what a 102v is so I don't know if you got the truck alternator or the F body alternator. If you got the f body alternator I'd say you need to be prepared to change it in roughly a week or two. Seems to be the standard with rebuilt/"new" f body alternators
Teching In
Joined: Aug 2012
Posts: 5
Likes: 0
From: tx
Hate to say it but it's rebuilt so the quality delphi stuff is likely gone. I'm not exactly sure what process you went through to change the alternator but if it was your first time then I can see it taking a while, but after you do it a couple times it's super easy. I've always felt it was super easy from the first time, but I'm a tech by trade so this is what I do for a living.
Hope it works out for you, I have no idea what a 102v is so I don't know if you got the truck alternator or the F body alternator. If you got the f body alternator I'd say you need to be prepared to change it in roughly a week or two. Seems to be the standard with rebuilt/"new" f body alternators
Hope it works out for you, I have no idea what a 102v is so I don't know if you got the truck alternator or the F body alternator. If you got the f body alternator I'd say you need to be prepared to change it in roughly a week or two. Seems to be the standard with rebuilt/"new" f body alternators
