Only cheap HEI works

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HTMLmopars

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Last night I went to put fuel in the 68, and after starting up easily and going about a block down the road, she started running really rough, like 1/4 throttle to keep it idling at less than 500 rpm. Limped back to the garage, hoping for a vacuum leak, or something obvious, didn't find anything. Eventually, I took off my brand new FBO ignition, and took the factory dizzy out, put in my $50 ebay HEI dizzy, ran perfect after I did that.
This is my second ignition box that I've had problems with, first a Mallory 690 box, now the FBO. I'm wondering if funky wiring in the car could be partially to blame. I'm running a squareback alternator, with one terminal grounded back to the case, and the voltage regulator that was on the car when I bough it. Is it possible that the charging system could be causing problems with the ignition system? My theory is that the nicer ignition boxes have tighter tolerances than the cheapo HEI, which is why the HEI works when the others don't.
 
China is a *****!! There are not too many options except to keep swapping stuff out until you find one good one that works for a long time. I use the Accel Super coil, after buying a few from China I finally bought one from the 80s (used on ebay) and that solved all my problems. It's funny how a 30 year old coil works better than a brand new one from China?????:poke::mad::soapbox::BangHead:
 
68Valiant225 said:
Last night I went to put fuel in the 68, and after starting up easily and going about a block down the road, she started running really rough, like 1/4 throttle to keep it idling at less than 500 rpm. Limped back to the garage, hoping for a vacuum leak, or something obvious, didn't find anything. Eventually, I took off my brand new FBO ignition, and took the factory dizzy out, put in my $50 ebay HEI dizzy, ran perfect after I did that.
This is my second ignition box that I've had problems with, first a Mallory 690 box, now the FBO. I'm wondering if funky wiring in the car could be partially to blame. I'm running a squareback alternator, with one terminal grounded back to the case, and the voltage regulator that was on the car when I bough it. Is it possible that the charging system could be causing problems with the ignition system? My theory is that the nicer ignition boxes have tighter tolerances than the cheapo HEI, which is why the HEI works when the others don't.
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A simple voltmeter can tell you if you are overcharging. Beyond that, most mallory/msd type boxes are pretty simple wiring. With just a 12v to turn it on. A few wires to the battery/dist, done.

I have never liked the oem ignition, or ANY of the oem appearing boxes. Wiring on these cars was crap 50 years ago. Anything you can do to isolate the engine from more than a 12v interface from the car is money well spent IMO. Unless of course you are in "ain't broke don't fix it" mode with the OE setup...But clearly not the case here.

I would go back to something like this.

IGNITION BOX | DIGITAL W/ REV LIMITER | BLACK
 
Johnny Mac said:
A simple voltmeter can tell you if you are overcharging. Beyond that, most mallory/msd type boxes are pretty simple wiring. With just a 12v to turn it on. A few wires to the battery/dist, done.

I have never liked the oem ignition, or ANY of the oem appearing boxes. Wiring on these cars was crap 50 years ago. Anything you can do to isolate the engine from more than a 12v interface from the car is money well spent IMO. Unless of course you are in "ain't broke don't fix it" mode with the OE setup...But clearly not the case here.

I would go back to something like this.

IGNITION BOX | DIGITAL W/ REV LIMITER | BLACK
Click to expand...

@Johnny Mac who makes that and where is it made?
 
68Valiant225 said:
I have the ammeter bypassed, by I'll double check my connection with those ring terminals.

Also what is considered truly overcharging? A constant 15?
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Yes. 15 I would call overcharging. 14.7 max is what I usually look for.

Make sure you bring the rpm up to check also.
 
Johnny Mac said:
Yes. 15 I would call overcharging. 14.7 max is what I usually look for.

Make sure you bring the rpm up to check also.
Click to expand...

I just came up with a plan to use the ammeter as a point to grab voltage from with a multimeter, and I'll drive with the multimeter running, see what it does with rpm, and load, with stereo and headlights, etc on
 
68Valiant225 said:
I just came up with a plan to use the ammeter as a point to grab voltage from with a multimeter, and I'll drive with the multimeter running, see what it does with rpm, and load, with stereo and headlights, etc on
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I mean you can check it on the stud of the alternator, make sure it's charging. May go clear up to 16 when revving on the actual alternator post.

Now the battery terminals can be tapped to check it AFTER the voltage regulator. By 2k it should be at peak charge after the reg. Maybe 2500 tops. If it peaks at 14.7 ish you are fine. 15 is too high. 13.8 is probably what I would call low ( at RPM). My numbers aren't exact, just off the top of my head hot rodder math. But will get ya close.
 
68Valiant225 said:
I have the ammeter bypassed, by I'll double check my connection with those ring terminals.

Also what is considered truly overcharging? A constant 15?
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Yup that's over charging usually it's due to a bad voltage regulator don't bother buying one at autozone or oriellys the got a big batch of faulty regulator from china, I fixed my over charging with the black mopar boxes on amazon for 36.00 bucks.
 
Slantsix64 said:
Yup that's over charging usually it's due to a bad voltage regulator don't bother buying one at autozone or oriellys the got a big batch of faulty regulator from china, I fixed my over charging with the black mopar boxes on amazon for 36.00 bucks.
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Is napa any good for them, or is legit mopar the onyl way to go. Also, I think I've read about going to the later model voltage reg with the later style alternator, which I already have. Something about solid state and being more robust. Is that true, or just buy a 68 box and throw it in the car?
 
Johnny Mac said:
Yes. 15 I would call overcharging. 14.7 max is what I usually look for.

Make sure you bring the rpm up to check also.
Click to expand...

Yet up there ^^^^ you said isolate the engine from more than 12V. :realcrazy:
 
68Valiant225 said:
Is napa any good for them, or is legit mopar the onyl way to go. Also, I think I've read about going to the later model voltage reg with the later style alternator, which I already have. Something about solid state and being more robust. Is that true, or just buy a 68 box and throw it in the car?
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Oh dang I though you had the later alt and voltage regulator. I would upgrade to the later style always brighter lights etc.
 
Slantsix64 said:
Oh dang I though you had the later alt and voltage regulator. I would upgrade to the later style always brighter lights etc.
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Yeah, I upgraded the alt when it went out the first month I drove the car, which was in 2015. Didn't know much then, so never changed the voltage reg, and since it charges, I never gave it second thought. Does anyone know the part # for the solid state stuff off the top of their heads, or should I just use the convenient search bar? Definitely will go for the quality part, charging system is worth spending money on
 
68Valiant225 said:
Yeah, I upgraded the alt when it went out the first month I drove the car, which was in 2015. Didn't know much then, so never changed the voltage reg, and since it charges, I never gave it second thought. Does anyone know the part # for the solid state stuff off the top of their heads, or should I just use the convenient search bar? Definitely will go for the quality part, charging system is worth spending money on
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I think that would be your problem running the early regulator with the later alternator here's the link for the later regulator https://www.amazon.com/dp/B003U2O6YQ/?tag=joeychgo-20
 
Slantsix64 said:
I think that would be your problem running the early regulator with the later alternator here's the link for the later regulator https://www.amazon.com/CHRYSLER-PLYMOUTH-VOLTAGE-REGULATOR-RESTORATION/dp/B003U2O6YQ/ref=sr_1_3?crid=1AX1PJZCWR8AR&keywords=mopar+voltage+regulator&qid=1574547580&sprefix=Mopar+regulator+,aps,807&sr=8-3
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Thanks!
I read somewhere a while back that grounding the second field wire of the alt to the case allows you to run the old voltage reg, but that's only helpful if your voltage reg is actually working
 
How does the later regulator connector splice into the early car's harness? It's been like 25 years since I've done one and caint remember.
 
RustyRatRod said:
Yet up there ^^^^ you said isolate the engine from more than 12V. :realcrazy:
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Isolate it from anything other than a "12v switched ON" is how It was intended to be read. The "hot" lead where It draws power goes right to the bat. Most boxes can operate clear up to 16v. The "on" is the "interface" and even that can just be a toggle switch. I know you know this.
 
Slantsix64 said:
Looks like this box probably China, for 100 bucks less TSP JM6931BK Digital Ignition Control Box, With Rev Limiter Black | eBay
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There are only 200 companies overseas making physically identical boxes, distributors, etc. And they all claim to be making them for msd also. Not my first Rodeo. We deal direct with a manufacturer. We don't deal with rebranding middle resellers. Not that any of it is relevant to the thread. Things just aren't always what they seem. Everybody makes a better mouse trap lol
 
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Been using the stock black/ chrome box from advance auto for about 6yrs not one problem but i added a ground wire.
 
Johnny Mac said:
Isolate it from anything other than a "12v switched ON" is how It was intended to be read. The "hot" lead where It draws power goes right to the bat. Most boxes can operate clear up to 16v. The "on" is the "interface" and even that can just be a toggle switch. I know you know this.
Click to expand...

I do, but you'd probably be surprised at what I "don't" know about electrical. I'm electrical stupid.
 
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