gm hei to amc

I have a hei from a gm 250 i6 what exactly is the difference as far as the gear end ive heard that you flip the gm gear over and it works is this true or would you use the gear off the old one in the jeep not looking to change it now just want to be ready if needed....

 

I cant remember for sure but I think you use the gear from a 304. I researched this at one time before just ordering an HEI from 4Wheel Parts for a $100. I looked at what I would spend making a used distributor work and it was easier and cheaper to just buy one.

 

I believe the original Jeep 6 cylinder gear doesn't work because the gear helix (slant of teeth) is in the wrong direction. Cj5dave is right in suggesting that you will have to use an AMC V-8 gear. There have been problems in some AMC HEI installations with the drive gear wiping out the cam gear in short order because the distributor drive gear used was hardened. It has been suggested that the installer do a file hardness test on the gear he plans to use. Try filing a non critical are of the gear. If the file will bite into the gear, it should be OK. If it wiil not bite and skids off the gear, it can assumed the gear is hardened.

 

no, you do not use the gm dizzy gear.

the 4wheel parts dizzy is cheesy, made with inferior materials. a gm-source hei is a far better route to take if you've decided to make the conversion.

no and no. the original gear WILL work. you aren't changing the cam. the original obviously has the correct orientation, since it was installed in the original dizzy/cam combination. you do NOT have to use an amc v-8 gear, although the amc v-8 gear will work.



you can use the original 258 drive gear, but you'll need to grind off some material from the gear in order for it to work. i've done it, and it's sitting in my jeep right now, and works fine. i used nothing more than a bench grinder with a coarse and a fine wheel to remove part of the collar from the gear. there are several good writeups on the net. most 258 motors are old and the original dizzy gear/cam are worn together, so they match up well, plus, why shell out $30-$50 for a new gear on an older motor?

 

i got the hei distributor from a 1980-sourced chevy with a 250 motor, which had the coil in the cap. i used the distributor drive-gear from the original amc prestolite distributor - it fits fine, but it needs to be modified. there is an extended section on the gear that doesn't have teeth, sort of a "collar". grind most of this off with a bench grinder, and it will fit the hei distributor, using the roll-pin from the original to lock it in place. for plug wires, i used a new set intended for a mid-1980s ford 300 motor, as the ford dizzy was located in about the same place as the amc dizzy on a 258/232 (near the "center", while the chevy 250/290 dizzy is located closer to the end - therefore plug wires are a closer fit. pretty sure i bought 8mm at autozone. run one key-hot power source to the distributor and fire it up.

 

Oh hell, what was I thinking. Of course the original AMC gear has the correct helix angle. I was thinking of the original Chevy HEI gear. I think the original AMC 6 cylinder gear needs to be shortened some. My bad and sorry for any confusion. I think I need to go back to sleep!

 

All good info and correct. There were some GM HEI 6 cylinder units with different shaft diameters as well. That's why you can use the 6 cylinder gear with some "massaging" on some and why you must use the V-8 gear on others. Done the conversion several times and with some patience it always worked out great. Good solid improvement in idle quality, ease of starting, even fuel economy in most cases.