Hei conversion troubleshooting

[smokinnjokin]

Greetings all.
I just completed an HEI conversion on my 360, and am having an issue that I believe is due to insufficient voltage to the coil+module. I spliced a factory style gm coil connector into my old points harness, eliminated the ballast and spliced those connections together also. I used crimp and solder connections, and it runs like a top until i try to rev up past about 2k then ignition cuts out sporadically. I diagnosed this with timing light, it goes intermittent and engine runs like **** and backfires when revved past about 2k.

Brand new standard ignition FD478 coil, LX-301 ignition module (not the cheap "T" models, the good ones). Both are independently grounded to the block. New 8mm wires and brass terminal cap.

All the instructions I have read say that the coil should be supplied with a 12gua wire. The factory harness is 18gua I believe, and the factory coil connector had even smaller, 20 or so. Does this seem like the source of my problem?

If so, it seems that my only option is to get 12v constant hot with a 12gua wire off the starter relay lug, and use a relay to switch it on to the coil.

HEI experts, please chime in!

If you are going to tell me to buy an MSD 6A box, or that points worked fine, or some other HEI unrelated advice, please move along! No disrespect intended, but that's not helpful to this situation.

 

[Garrett Ellison]

Do a voltage drop test on the 12 volt power to the HEI and see if the voltage is falling off when the rpm comes up. I forgot the voltage range that most factory replacement modules have, but a quick search at standard ignition parts should have it for your module. It could also be a rotor/reluctor phasing issue. But going by symptoms alone, my first instinct is that is what a bad HEI module acts like. Know anyone with a Suntune machine?

 

[mod5v]

Try unpluging your tach signal wire. also make sure the magnetic pickup in the dist is wired in correct phase.

 

[BigBlockMopar]

Reversed polarity on the distributor pickup?

 

[Frank Mopar]

All good pointers.

I have a relay running mine. I even left the ballast but pulled the resistor out of it. Of course the wires from the ballast just close the relay

 

[ch1ll]

Sorry for your troubles, GM parts on a Mopar, never a good idea.

 

[Frank Mopar]

Sorry for your troubles, GM parts on a Mopar, never a good idea.

Start here.

Spark It Up: How to Convert a Ford or Mopar Distributor to GM HEI

 

[TrailBeast]

View attachment 1715368598 View attachment 1715368599 View attachment 1715368600 Greetings all.
I just completed an HEI conversion on my 360, and am having an issue that I believe is due to insufficient voltage to the coil+module. I spliced a factory style gm coil connector into my old points harness, eliminated the ballast and spliced those connections together also. I used crimp and solder connections, and it runs like a top until i try to rev up past about 2k then ignition cuts out sporadically. I diagnosed this with timing light, it goes intermittent and engine runs like **** and backfires when revved past about 2k.

Brand new standard ignition FD478 coil, LX-301 ignition module (not the cheap "T" models, the good ones). Both are independently grounded to the block. New 8mm wires and brass terminal cap.

All the instructions I have read say that the coil should be supplied with a 12gua wire. The factory harness is 18gua I believe, and the factory coil connector had even smaller, 20 or so. Does this seem like the source of my problem?

If so, it seems that my only option is to get 12v constant hot with a 12gua wire off the starter relay lug, and use a relay to switch it on to the coil.

HEI experts, please chime in!

If you are going to tell me to buy an MSD 6A box, or that points worked fine, or some other HEI unrelated advice, please move along! No disrespect intended, but that's not helpful to this situation.

Try reversing the two wires for your distributor.
Very common for them to get swapped or connected backwards.
What happens is the coil fires too late when they are reversed and when mechanical timing starts coming in the rotor is close enough to the next contact in the cap (the wrong contact) the spark jumps to it instead causing backfires.
If not that it sounds like the module, as I have had one do that to me before.

 

[smokinnjokin]

Thanks all for the tips. I did have a voltage drop, so I wired up a relay today, 12g wire direct from starter relay terminal. Did not fix the problem, seemed to get slightly better but still overall ran like garbage and backfired when rev'ed up. Timing light confirmed that ignition was cutting out sporadically, checked several different plug wires same problem.

The ignition module and coil are both grounded independently, and barely warm when this problem is occurring.

Next, I will test a new module, (this thing is brand new, if its bad what the hell).

The distributor is still my prime suspect, It is one of the R. Ehrenberg ebay ones and the reluctor wheel was really poor quality, all different lengths make it hard to gap properly. I did swap the pickup wires to check that, the car wouldn't idle and REALLY ran like garbage with them switched so that's not the problem.
I have already contact a FABO forum member to get a rebuild OEM distributor, but for now I'm trying to eliminate any other possible source of the issue.

 

[skidmark]

When you switched the distributor wires was the timing still ok?

 

[smokinnjokin]

****, I didn't even think of that. Let me run out and check.

 

[smokinnjokin]

Ok, so i switched wires, made the radical timing alteration necessary for it to show 10btdc and idle properly. It still does the same thing, spark gets intermittent and it starts running shitty when revved up. So I think its safe to say that's ruled out.

 

[smokinnjokin]

Try unpluging your tach signal wire. also make sure the magnetic pickup in the dist is wired in correct phase.

Tach signal wire isn't hooked up, has a wire nut on it.

Sorry for your troubles, GM parts on a Mopar, never a good idea.

Even with this issue, the difference with HEI is very noticable. You barely bump the starter and it fires right up. Hot starts after it has been sitting a while are the same. I hate points, and I have never been a fan of the factory chrysler electronic ign system.

 

[superchargeddrt]

Is there any play in your distributor? I had one of those cheap TSP distributors (MSD copy). The end of the shaft fit poorly into the distributor gear and there was about 20 degrees of play in the distributor rotor. Wound up buying the MSD distributor.

 

[smokinnjokin]

Is there any play in your distributor? I had one of those cheap TSP distributors (MSD copy). The end of the shaft fit poorly into the distributor gear and there was about 20 degrees of play in the distributor rotor. Wound up buying the MSD distributor.

There is a little, my best guess would be between 3-5 degrees. Not terrible. No shaft play in the distributor off the car, it just slop where the end of the shaft fits into the gear same as yours.

 

[Garrett Ellison]

It's probably the ignition module. The real problem is that it's almost impossible to avoid some kind of Chinese manufacturing somewhere along the way. But since your going HEI anyway, I have read a lot of good things about these units. I have a friend that uses them on his conversions, and has not had one go bad yet.
Davis Unified Ignition Dyna-Modules 000222

 

[smokinnjokin]

It's probably the ignition module. The real problem is that it's almost impossible to avoid some kind of Chinese manufacturing somewhere along the way. But since your going HEI anyway, I have read a lot of good things about these units. I have a friend that uses them on his conversions, and has not had one go bad yet.
Davis Unified Ignition Dyna-Modules 000222

Reading the description for that ignition module made me realize I did not continue the 12gua wire to the module, just to the coil. There's still an 18 wire going from coil to module. Probably nothing... but I might as well rule it out. I have another LX-301 module that I will try out tomorrow. Have to pull dizzy since its mounted underneath. I'm over this project for tonight. I guess i could take my modules to an auto parts store and have them tested.

 

[skidmark]

I just did the HEI conversion, so far works great. You’ll get it. Did you twist the wires from the module to distributor?

 

[skidmark]

Did you disconnect and plug vacuum hose from distributor when checking timing?

 

[skidmark]

I filed my reluctor so I could get the same gap all around. The metal is soft so be careful. Set mine at .008
Your motor was running fine before HEI?

 

[smokinnjokin]

I just did the HEI conversion, so far works great. You’ll get it. Did you twist the wires from the module to distributor?

Yes, wires are twisted together.

Did you disconnect and plug vacuum hose from distributor when checking timing?

Yes.

I filed my reluctor so I could get the same gap all around. The metal is soft so be careful. Set mine at .008
Your motor was running fine before HEI?

Motor ran well before HEI, but I did a intake manifold swap, new timing chain and lifters in conjunction. Cured my lifter noise. Ruled out anything mechanical, I think the intermittent spark from the timing light coinciding with the crappy running pretty much gurantees this is an ignition problem.

Did you try running that crappy reluctor before filing it? I am curious if this could be the cause of my issue, having a hard time picking up the signal at higher rpm's. Gap varies about 0.05" to 0.15" right now. It was touching on some when i first got it. It had apparently been gapped at 0.08" from the factory, but on one of the shorter arms.

 

[67Dart273]

Any chance the module is not getting a good ground? How about heat sink? It must sit nice and flat on a surface to dissipate heat

I would increase wire size to the module (you said 18?) but frankly doubt that is this problem

There is only one correct polarity for the pickup wires. It's called "rotor phasing" Google that. If the dist. has been apart, or something slipped etc the phasing can be off. This refers to the point in rotation at which the spark is triggered vs where the rotor is pointing in relation to the cap contacts. If this is off, the spark triggered between cap contacts, it will run poorly. Crossfiring, etc. A timing light alone will not show this up

At this point I would "just try" another coil ANY coil. I actually used a factory Mopar coil on my conversion.

Other than what's been covered above, no new ideas. If you have a spare dist. I'd try it too

 

[smokinnjokin]

Any chance the module is not getting a good ground? How about heat sink? It must sit nice and flat on a surface to dissipate heat

I would increase wire size to the module (you said 18?) but frankly doubt that is this problem

There is only one correct polarity for the pickup wires. It's called "rotor phasing" Google that. If the dist. has been apart, or something slipped etc the phasing can be off. This refers to the point in rotation at which the spark is triggered vs where the rotor is pointing in relation to the cap contacts. If this is off, the spark triggered between cap contacts, it will run poorly. Crossfiring, etc. A timing light alone will not show this up

At this point I would "just try" another coil ANY coil. I actually used a factory Mopar coil on my conversion.

Other than what's been covered above, no new ideas. If you have a spare dist. I'd try it too

Module is mounted to the designed2drive aluminum heat sink, with thermal grease. Has a dedicated ground from mount sleeve to block.

The distributor is brand new, ebay from R. Ehrenberg. For all I know, the rotor phasing could be off. The coil is an e-core, is grounded and keeping cool, but I will try my old coil. At this point burning it up with a full 13+ volts isn't a big deal. I guess it only takes a few minutes to rule out the coil as the culprit.

 

[skidmark]

Motor ran well before HEI,
Did you try running that crappy reluctor before filing it?

No I didn’t run it first. I replaced a no name unidentifiable distributor that did run with Chrysler orange box, but I had issues with it jamming rotor into the cap. I fixed that internally. Didn’t have any confidence in it for reliability so I bought a rebuilt OEM electronic at Napa. Took it apart and rebuilt it again with FBO advance limiter disk, changed 1 spring out for a lighter spring on advance weights. And added metal collar setting shaft play with shims and reworked reluctor and set gap. So far so good.

Any chance it’s going lean? Clogged fuel filter? Fuel pressure ok?

New lifters.....Just double checking, You did a break in like a new cam?

 

[smokinnjokin]

No I didn’t run it first. I replaced a no name unidentifiable distributor that did run with Chrysler orange box, but I had issues with it jamming rotor into the cap. I fixed that internally. Didn’t have any confidence in it for reliability so I bought a rebuilt OEM electronic at Napa. Took it apart and rebuilt it again with FBO advance limiter disk, changed 1 spring out for a lighter spring on advance weights. And added metal collar setting shaft play with shims and reworked reluctor and set gap. So far so good.

Any chance it’s going lean? Clogged fuel filter? Fuel pressure ok?

New lifters.....Just double checking, You did a break in like a new cam?

Filter is good, steady 5psi pressure, a lean condition is possible but I don't see how that could cause the ignition to cut out at higher rpm's. It would explain the backfiring/poor running, but not the intermittent spark (at the wire, indicated by the timing light).

I tried to do a proper break-in, but the crappy run condition meant I couldn't rev it up past 1500-2k. I used good break in lube and high zinc oil, and there is no ticking or anything so hopefully break in was ok. When I can get it to rev up to redline without breaking up there is no noise from the valvetrain. Basically it hasn't had any run time under a real load. A lot of idling and bouncing rev's.