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77 alternator fit


Speedracer906

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You need a truck alternator. They are smaller diameter than the regular car ones even though they are the same engine. The truck alternator is about 35amp. The car alternators are larger and 50/60 amp. I have fitted one before but a lot of bother. They tend to hit the idler arm below them when you adjust the belt ot to tension it.

 

 

Take note that the '77 and earlier alternators require an external voltage regulator. It's that squarish, rounded corner thing, about the size of your fist located to the rear of the battery. Often when they fail a newer internal regulated alternator, '78 and up, is installed and the wiring 'converted' and the regulator removed.

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Ok, so I'll hold off on finding an alternative bracket then. My bracket has as many holes as does my block. (3)

The regulator is still in place, I'll note the possible, future mod if the external reg fails. Does the 78 and up Alternators have a higher amprage? Might be a mod worthy of instigating preemptively.

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Only alternators I have seen all have the Hitachi symbol cast into them. Truck alternators are slightly smaller and early ones are 28 amp ('73) later are 35/38 amp. The 50/60 car alternators bolt right in but because they are larger diameter they sit farther out from the block and when belt adjustment is set they rub the idler arm.  Search google with.... " alternator up grade for 620 . ratsun" there are GM alternators that will fit but they are all internally regulated.

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No such car. :lol: j/k

 

I found I had to put the belt over the pulley first then bolt it in. It was the only way to get a short enough belt on so it didn't hit the idler arm. It also had a 720 alt. to block mount which raises the alt about a bolt width and a 280z lower rad hose to timing cover inlet. This inlet is more swept back for additional clearance of the higher and larger diameter alternator just below it. It worked but the belt had no adjustment left and once it stretched I had to buy a new one.

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There were Mistubishi alternators that fit L-series engines, but they were all pre 1972 or got swapped in later as they still fit.  All 620s came with Hitachis, and it didn't matter if they were internally or externally regulated, they were 35A.  It's possible to get the larger diameter car alternators to work, per Mike above.  Saturn (or any Delco alternator) conversions have a similar clearance issue, but I've found that the condition of your motor mounts has a lot to do with how well the larger diameter alternators fit.  The more wore out the mounts, the lower the engine sits and moves around, hitting the idler arm with the alternator.  One of my trucks had a hole worn in the alternator case from rubbing when I got it.

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Well, "guaranteed to fit" is being called into question...

I recieved an Ac Delco 334-1547 and it smells like a duck, that is to say, if it looks like the same as the car one I also recieved and mounts like the car one, it must be the same as the car one. Mount holes too small for the bolts that fit into my mount, cannot rotate alt due to idler arm and zert fitting.

Again, can the mount be -also -giving me some trouble? Should I go to NAPA instead of Autozone? Should I just plan on doing the Saturn alt swap??? I'd take a pic and post but...photobucket! For the record,the alternator(s) I recieved for the 77 620 does not look like the photo on anyones site that claims "guaranteed to fit".

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The computer will call up both options with a note below each stating something like "Hitachi" and "Mitsubishi", so long as the computer is aware of there being multiple options.

 

Also, don't be a dick to the parts guy. He will purposefully give you wrong parts to screw with you.

 

#11yearsatoreillyautoparts

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  • 2 weeks later...

I think you'll find the alternator swings and hits the idler arm just outside the stock adjustment range. If this worked everyone would be doing it. Most go for higher output smaller alternators. Car and 720 50/60 amp are too big to work well. Mine was so tight I had to put the belt over the pulley first then bolt it in.

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Perhaps the pulley is positioned closer to the block?

 

I had a '78 620 and tried a 720 alternator which was physically slightly larger diameter. There was a definite problem with clearance with the lower rad hose, the water inlet pipe and the idler arm right below it when you swing it away from the block to tension it. I used a shorter belt but had to put the belt on the pulley first and then bolt the alternator in. Anything else the belt was too long. Even then I used a 280zx water inlet pipe that swings farther to the rear and a 720 alt mount bracket to lift the alternator about 1/2". This allowed you to tension the belt but... once it wore down or stretched it would rub the idler arm grease fitting.

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  • 2 weeks later...

Well, back at it.

I came home with a GM mini...sacralige I know.

I’ll search up the wiring steps now. The best part of the fit was that IT FIT!

I had an altinator bracket that was more like flat metal, instead of the molded/curvy one. This gave me a nice flat surface to butt up the single horned GM to. The bolt sizes are off, meaning the mount takes a 10mm and the GM altinator mount hole is larger. If I get all fussy with the mod I’ll grind off the existing bolt and up size it so that the altinator doesn’t wiggle around when loose. When everything is tight the altinator is fine as is. I can’t believe how much room I have down there.

 

Update:

I just confirmed that this Denso 12170 is 35 amps.

 

 

Just ran across this post, it’s also about the Saturn Alt.

http://community.ratsun.net/topic/7830-saturn-alternator-how-to-wire-in/

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