1975 CJ5 no spark issue

[grabeb]

Buddy has an old beater CJ5, I am pretty sure it's a 1975 with the prestolite ignition system and the 4.2L(?), he keeps getting intermittent spark and he's been reading that is a nightmare system. So the question at hand is replacing with HEI distributor. Any feedback on this? I've converted an old SBC350 to HEI, so I know it's pretty straight forward, but anything specific on this? I plan to try to see what that distributor crosses to, maybe he can find one easier. He's trying not to spend much on this project as it is a beater that he wants to take and leave at the 'farm'. It appears Jegs has one for about $100, which is fair if it's any good. But I know AMC used random parts from random stuff back in the day.

I guess any tips on which wire to grab from for the feed? I know it needs to be 12v high amp wire. Then since it's been a couple of years since I've restabbed a distributor, any tips on that. Can i just mark where the current is pointing and stab the new to that same point? I believe that's how I restabbed my SBC350 a few years back without having to get to TDC.

I'll also google this and see what info I get, but thought maybe some insite here as well! Thanks!!

 

[Chris]

Buddy has an old beater CJ5, I am pretty sure it's a 1975 with the prestolite ignition system and the 4.2L(?), he keeps getting intermittent spark and he's been reading that is a nightmare system. So the question at hand is replacing with HEI distributor. Any feedback on this? I've converted an old SBC350 to HEI, so I know it's pretty straight forward, but anything specific on this? I plan to try to see what that distributor crosses to, maybe he can find one easier. He's trying not to spend much on this project as it is a beater that he wants to take and leave at the 'farm'. It appears Jegs has one for about $100, which is fair if it's any good. But I know AMC used random parts from random stuff back in the day.

I guess any tips on which wire to grab from for the feed? I know it needs to be 12v high amp wire. Then since it's been a couple of years since I've restabbed a distributor, any tips on that. Can i just mark where the current is pointing and stab the new to that same point? I believe that's how I restabbed my SBC350 a few years back without having to get to TDC.

I'll also google this and see what info I get, but thought maybe some insite here as well! Thanks!!

Switching from the Prestolite ignition to an HEI distributor is a great idea, especially considering the reliability issues you mentioned with the original system.

Regarding the HEI installation, here are a few tips:

You’ll want to ensure you find a good 12V source that’s hot in the “run” position, ideally not the ignition coil wire since it may not provide enough current for the HEI. A common choice is the factory wire that goes to the ignition coil, but it needs to be connected to a straight 12V supply when the key is in the “run” position. You might want to add a relay to ensure it gets adequate current, depending on the setup.

Yes, marking the position of the current distributor before removing it is a good strategy. Just make sure to get that mark as precise as possible to help you line up the new one correctly. However, keep in mind that if the engine has been running poorly or has jumped time, double-checking the timing mark on the crankshaft is also a good idea to avoid any timing confusion later.

As for the distributor, you've got the right idea to check for cross-compatibility with other models. Sometimes, you can find a suitable HEI that fits from another brand or model, which can save you money. Aftermarket suppliers sometimes have listings that give you options based on your engine year and specs.

Once it's in, it's generally a straightforward setup. If you can, check your spark plugs and wires too, as they can sometimes cause secondary spark issues.

Expect smoother running and potentially better fuel efficiency with the HEI setup. Just remember to set the timing after you’re finished; that can vary quite a bit depending on the exact setup.

 

[grabeb]

Switching from the Prestolite ignition to an HEI distributor is a great idea, especially considering the reliability issues you mentioned with the original system.

Regarding the HEI installation, here are a few tips:

You’ll want to ensure you find a good 12V source that’s hot in the “run” position, ideally not the ignition coil wire since it may not provide enough current for the HEI. A common choice is the factory wire that goes to the ignition coil, but it needs to be connected to a straight 12V supply when the key is in the “run” position. You might want to add a relay to ensure it gets adequate current, depending on the setup.

Yes, marking the position of the current distributor before removing it is a good strategy. Just make sure to get that mark as precise as possible to help you line up the new one correctly. However, keep in mind that if the engine has been running poorly or has jumped time, double-checking the timing mark on the crankshaft is also a good idea to avoid any timing confusion later.

As for the distributor, you've got the right idea to check for cross-compatibility with other models. Sometimes, you can find a suitable HEI that fits from another brand or model, which can save you money. Aftermarket suppliers sometimes have listings that give you options based on your engine year and specs.

Once it's in, it's generally a straightforward setup. If you can, check your spark plugs and wires too, as they can sometimes cause secondary spark issues.

Expect smoother running and potentially better fuel efficiency with the HEI setup. Just remember to set the timing after you’re finished; that can vary quite a bit depending on the exact setup.

Thanks, I'll see if AI can point me to a good starting point on the wiring and maybe the timing set. I do have a timing light if needed. The engine seems to run great when it runs. He swapped out the coil, then tried to swap out the module and found some bad wires in that plug so realized it wasn't the module, but now it seems he's just going to keep throwing parts and likely end up at ground zero. On my SBC, I think I tapped into the horn relay wire, so I'm hoping something like that is available on this. But I'm sure we can find it.

If anyone has the timing specs that would be great, otherwise we should be able to go by sound if we get close. I think I nailed it dead on on my SBC, so I know it isn't hard but it does intimidate most.