Hesco MPI 82 CJ7 4.2l

[hawkrider]

Anyone else have the Hesco Mopar MPI kit on a AMC 258 i6 / 4.2l ?
According to the instructions for the kit, the ignition timing should be 10-12deg BTC. I had previously always set mine at 15deg BTC as per my original Jeep shop manual. I recently checked the timing just for grins and found it to be at 16deg BTC. This seems to be a big difference and I don't know how to adjust it. Other than some occasional ping under load she seems to be running just fine so maybe I'm just over thinking it?
Any input or suggestions appreciated.
Lou

 

[hole]

The pinging has more to do with the AMC 258 i6 / 4.2l head than anything else. I tried adjusting the timing some, running premium fuel, etc.... Swapped to a 4.0 head, no more pinging under any circumstance.

 

[Lumpy Grits]

Try premium gas, to get rid of the ping.
You'll have to have the timing correct to pass SMOG.

LG

 

[hawkrider]

Thanks for the advice. This has been an on going project for the last 4-5 years including a rebuild.

Lumpy. Interesting that you mentioned the SMOG issue. I've SMOG'd it twice since rebuild and adding the MPI and it passes with flying colors. I even asked the tech about the timing and he said it was fine but didn't give me the number. I'm not sure he even checked. Been going to the same guy for over 10 years now. He didn't even flinch over the MPI addition. He just glanced at the engine, paperwork and CARB sticker and ran the test.

That's why I'm questioning the timing issue. It runs good and passes CA SMOG, but the timing is "off" from the HESCO spec by 6 degrees? Doesn't sound right.

Lou

 

[Lumpy Grits]

Strange-I'm still run'n the OEM carb set-up, and get a full print-out from my SMOG guy.
Might be different with the FI.
Have you tried running premium gas for a couple of tank fulls?
Check your instructions etc to see if a minimum octane rating was mentioned.
I would also call the Hesco about this--
LG

 

[hawkrider]

Sorry for the delay in updating this post. I have been in contact with Hesco, and their response: "The dist will not change ign timing, crank position sensor controls that. The dist controls injector timing and spark distribution. The timing can be changed by a DRB II or by spacing the crank sensor bracket DOWN with washers, 1/8" is 1 degree,
or you can send PCM to me and I can retard timing up to 6 degrees.... it will take 4 to 6 degrees to stop "PING". "

So I spaced the crank position sensor down by 1/2". That dropped the timing down to 12 BTC (was at 16-17). Seems to run good, but I need to take it out for a longer drive to see if the "ping" is gone. The spacer washers work, but seems like more of a band-aid fix. I think adjusting the PCM is probably the right way to go but I'm not real excited about sending it to Hesco in Alabama since these are impossible to come by.
But I'm confused. If the PCM sets ignition timing, why does it need to be adjusted? Shouldn't it have been set to run at 10-2 BTC (as stated in the installation instructions) from the start?

Hawkrider