1974 Alternator Questions

I have to replace the alt that came with the jeep, has blades behind the pulley that won't let it fit on the stock 1974 alt bracket. Alt mount at lower driver side

258 engine and no power steering or AC.

What is the correct pulley diameter?

If I look at an electric winch in the future, is it a good idea to buy a 55A alternator?

I have been looking at the following alternator on Parts Geek


Click to Enlarge

Remy Alternator
Part Number: 15685-05367084
Brand: Remy
Notes: Premium Remanufactured -- With AC; 55 Amps
Condition: Remanufactured
Voltage: 12
Amperage Rating: 55
OE Manufacturer: Motorola
New or Remanufactured: Remanufactured
Shipping Options: Ground

$40.43

Core Price : $29.00
Quantity:
(7) In Stock

 

Are you friends with your FLAPS? I'd ask them to order in whatever their book calls for as a replacement. They should help you if you are a good customer and you don't actually install the alternator.

Compare what they get you with the parts you have. Typically the higher the output, the more cooling air the alternator needs and the larger the fan blades. Looks like the standard alternator was 37 amps, and the "heavy duty" alternator was 51 amps.

A '74 can have an ammeter in the dash. If present, all the charging current goes up to the dash and through the ammeter. Don't send more current to the ammeter than it and its wiring can handle.

 

Check Rock Auto

I got a rebuilt alternator for my Jeep for about $35, it fit perfectly and charges well.

 

I cannot be absolutely sure but the pulley from your old alternator may interchange onto the new one. However as tim said if the new alternator is a higher output rating it may not cool as well with a smaller fan/pulley installed.
Alternator mounting brackets can be altered if you have the means of doing so. That is what I plan on doing with mine. I just purchased a 3 wire, 94 amp, 12SI Delco-Remy for my 304 engine, with the bigger fan and pulley and will surly need to modify things.

 

You might make the 10SI fit that bracket. I'd guess the 12SI is too big for the original bracket. Your friends at your FLAPS should have a 10SI in stock that you can look at and compare with your brackets.

 

I have just picked up the alternator yesterday. I have not yet looked at what all will be needed to modify it to fit my old Motorola mount. I did compare the 12si with a 10si at the flaps while there ,I also expected the 12si to be bigger however they appeared to be the same on mounting bosses and exterior size. The main difference appeared to be a bigger improved fan and more and larger air intake vent opening on the rear face.(the higher the amp rating the more cooling they require) The flaps man said the main difference between them is the interior coils, regulator and improved cooling capacity and so on . The 10si that I looked at was a clone of the Delco-Remy but it looked the same as the 12si except it just did not have the ''Delco-Remy'' stamp on the rear of the case.
I expect that the Delco will certainly mount a little different than the Motorola does, so mods will be in order for sure. I would guess if you do not have the means to modify your original mounts the only choice you have would be to stay with the 35 amp or optional 51 amp motorola that came factory. Jim

 

Humm, wonder where that coffee attachment came from.

 

Sometimes you have to "clock" the alternator to fit the application, but that is easy with a Delco Remy.

The one "Ol Fogie" provided a picture of is not clocked the way I would want for a right side application. I would rotate it one position clockwise to place the connectors closer to top, and the ground lug closer to bottom and the frame.

 

You are correct, I was just looking at that a few minutes ago. I was just wondering how much trouble it would be to clock it 90 degrees. Any suggestions? I would guess just remove the 4 bolts and turn it without separating the case .

 

Separate the case halves. You need a toothpick to hold back the brushes when you put it together in the chosen orientation. The toothpick goes in the small hole on the other side of the vents on the rear. Should be obvious when you pull the halves apart. Easy.

 

If you try this at home be aware that if you lift shaft too much the spring loaded brushes will pop out. If that happens there are small holes in the recess the brushes ride in which are used to re-install the brushes. You just push the brush and spring into the recess and insert a small wire, like a paper clip, or small drill bit, into that hole from the front of the alternator to hold the brushes out of the way while you insert the shaft. Then pull the wire out after you bolt the two halves back together.

A tooth pick would probably work, but I would worry about it breaking off.

 

Ah, Thankyou, I thought that might be needed.

 

The said holes, are they the ones rectangular in shape near the center bearing cap at 12 oclock and 8 0'clock? (see my photo above)

 

Single hole, at ca 4 o'clock, next to the hub.

 

This is the brush holder - you can see it comes with a pin to hold the brushes back.
https://www.ebay.com/itm/New-Alt-BR...or-Chevrolet-FD618D-W6853-39-101/383065957337

The pin goes in through the hole in the case I pointed to. Put the halves together and pull the pin to release the brushes.

It's obvious once you have the alternator open in front of you.

 

Ah, now it makes sense. Thank You very much. Merry Christmas!

 

And to you and yours!

 

Tomorrow morning I am going to a good alt, starter etc rebuilder and seeing about the pulley on my alt and find out about the output. I ordered the correct water pump for the jeep.

 

That sounds fine, but I think you are making this more complicated than it is. Some of the remans come with a pulley - look at RockAuto. The 2-groove pulley on your current alternator is not original.
https://www.rockauto.com/en/moreinfo.php?pk=12526405&cc=1180583&pt=2412&jsn=399
https://www.rockauto.com/en/moreinfo.php?pk=6681216&cc=1180583&pt=2412&jsn=401

You don't have to send away to RockAuto for an alternator, though you could. This is a very common alternator and your FLAPS (friendly local auto parts store) could easily get one. Ask - they should be willing to order one in and you can compare it to your brackets on the parts counter at the store. Simple.

 

Well, I done a little more research today. Looks like the Delco 12SI alternator is going to fit with very little mods to the factory 304 mount. The six cyl engines mount may be different?
However on my mount the bolt holes for the 12si are the same pattern as the Motorola alt has. Also the bigger pulley on the 12si will still clear the mount frame although close. [