alternator on gm/cummins conversion

Chevycummins

Chevycummins

Bad case of Tinkeritis!
Joined
Jul 15, 2008
Messages
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if it interest anyone i figured i would post how we got the alternator to work on my cummins conversion using the factory gm one. we took a piece of 1/4" steel and cut a pattern to reach from the lower and upper alternator bolt locations for the cummins alternator and then made it to where one of the three tabs bolted on the bottom to hinge it, then made the bracket with all thread to make an adjuster then used the bolt on the back to make a bracket to keep it from twisting. to get the belt to work we just swapped pulleys

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altsetup2.jpg
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I still honestly believe its just a whole lot easier to use the stock cummins alternator and have your alt shop set it up with an external tach wire and then use an external regulator mounted on the fire wall. My 88-98 style gm was a breeze to setup (took less than 20 minutes) and it even had studs on the firewall (by the clutch resivoir) that the regulator bolted right on too! Super easy, charging worked and the factory tach matched my big Autometer diesel tach so it worked great. Looked factory, nice and clean!

RyanB
 
We did this in a pinch, didn't have time to wait on a shop we did this conversion in a weekend left work Friday night went back to work Monday morning. If you are going to go through the trouble to have a tach pickup installed might as well make it a one wire set up also. Plus I don't have the tensioner pully either so this works to adjust the belt
 
yeah, its a good setup it you don't have the tensioner but I would have assumed that if you where to run the Dodge altenator the tensioner would have worked.

My main reason for doing so the way I did was that I wanted a supper clean install (whole conversion) that looked like it came from the factory with a 12valve between the frame rails. even my fan shroud I made at the time for it looked factory.
 
yeah we had limited time and i plan on getting the tensioner and alternator to replace that set up but i just figured i would share for those that might want to save a buck here and there to just used their gm one.
 
if it was a 6.5l alt., you just make some brackets/8 groove pulley and hook the factory plug and wires back and the factory tach works.

Joe
 
turbojoe said:
if it was a 6.5l alt., you just make some brackets/8 groove pulley and hook the factory plug and wires back and the factory tach works.

Joe
Click to expand...

thats what we did got an 8 rib pulley and swaped them out. had to clock the alt a little bit for how we bolted it up but all worked well it was a cheap somewhat simple fix once we got everything lined up.
 
the one thing i forgot to mention at the time i got the stuff from autoworld and they sent me a factory dodge or ford(dont remember) 8 rib and the tach was off at WOT it only showed like 2200 and they said on some alts. you need a small pulley, so they made me one and it works fine now.

Joe
 
yeah mine is off about 150 rpms at WOT not too bad for me to keep track of. i plan on going the extra and doing the dodge one with the one wire and tach pickup.
 
The tachs in these trucks are off all around. My tach reads roughly 700-725 when I know it's idling at 600. At 2000 it reads roughly 200 RPM's too high, yet when I'm at 3250 the tach will only show about 3100.
 
my alternator on the cummins is almost dead on at idle and gets off evenly as you go up to around 2000 on the gauge and the rpm tool that clamps on the injector line says i am around 150 rpms off.
 
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