HEI Distributor gear question

[evesdropper]

While I am waiting for my fuel pump to arrive, I started another project. I will do a write up later if anyone is interested (and it works).

I am swapping out the worn out distributor on my 1984 CJ8 with a 2.5l to a GM HEI franken-distributor. All is going well but I ran into a snag with the distributor drive gear. I searched the forums and could not find an answer.

The stock mac 2.5l drive gear has an ID of .5325". an HEI distributor shaft is .488 ". The stock gear also has no dimple indicating where the rotor should line up. I didn't think to mark it of course.

What I did find on searches was that with the AMC 258 i6 / 4.2l HEI swap, people seem to use an older AMC v8 drive gear. I happen to have one and it fits on the HEI shaft fine. However, It is quite a bit longer (1.625" from the AMC 304 vs 1.249" from the 2.5l).

Does anyone know which gear I should get to fix this mismatch?

I am thinking I have a couple options otherwise.

1. use the v8 gear and grind down the tailshaft until it is equal to the 2.5l
2. take the 2.5l gear to the machine shop and have it bushed to fit the hei shaft.

Option 1 seems the easiest but the gear portion is 0.1" shorter on the v8 gear. Maybe that does not matter.

Option 2 would fit for sure but I won't be able to determine if the rotor is lined up correctly. I believe the carb'd 2.5l had a bunch of advance built in already.

The best option would be for some wise sage to let me know which gear is correct.

Thanks for the help.

 

[Bent]

Use the AMC V8 gear on the GM HEI I6 and the 4 cylinder cap. You can also us a V8 cap and use every other post. I'm using the AMC V8 gear on a GM I6 HEI in my AMC 258 i6 / 4.2l . The bottom of the gear is longer but not the contact area. I tested the gear mesh with gear paint and had full contact. I saw no need to grind down the bottom of the gear. I did need to reduce the shaft a little by putting it in a drill press and turning it against some sand paper. There is no mark on the gear for rotor alignment, just the roll pin.

 

[evesdropper]

Ok good.

I used the distributor cap from a 1980 Chevy Citation, Distrubutor from a 1978 Chevy C10 250 I6, all the HEI guts are from a 1979 Chevy Camaro.

I need to grind off every other tooth on the reluctor and pickup coil yet. Once I figure out which to start with. For the reluctor, I am assuming the one directly under the rotor is the one to keep and file off alternate ones. Pickup coil will just leave the ones lined up with the 4 terminals on the cap.

 

[Bent]

Try to find a reluctor and pick-up out of one of the early 1980s gm FWD car with the the Iron Duke and big cap HEI. PM me your address and I'll send you the rotor/reluctor I have for the duke.

 

[evesdropper]

Try to find a reluctor and pick-up out of one of the early 1980s gm FWD car with the the Iron Duke and big cap HEI. PM me your address and I'll send you the rotor/reluctor I have for the duke.

You have a pm. Thanks.

 

[Bent]

Got your PM.
You will be getting the reluctor ring and the trigger rotor that slides over the shaft. So, you'll need to get a new trigger coil. It will be the same as the V8/V6. The only issue is aligning the parts. When you put the reluctor ring on the coil, just barely snug up the three screws so that the ring can move a little. Then with the distributor held vertical in a vise, spin the shaft slowly so the ring can self align. Then slowly tighten the screws while you turn the shaft. Just make sure there is no contact when you're done.