Help me diagnose my miss over 4500rpm.

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89on35s

Inferno Red Duster
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74 Plymouth Duster, 360, A-500, 8 ¼ w 3.23 sg. Running at 185 degrees (confirmed with good IR heat gun). 3/8” pick up in tank with -6 AN braided line between tank and fuel pump. New Carter HV fuel pump with Performance World regulator set to 6 psi. Fuel filter is perfectly clean. Holley 670 Street Avenger on an Edelbrock Performer 318/360 intake. Stock 1.88/160 J heads and unknown pistons (100PSI compression even on all cylinders when cold). Unknown cam, but definitely more duration than stock. Stock electronic ignition with cheap parts store ign. box with external ground jumper to case. I adjusted the reluctor gap to factory spec. Timing at 22 deg. btdc @ idle with total 34 deg. in at 2500 rpm. I messed with it for a quite a while and it runs best there. I just redid my intake gasket due to a bad vacuum leak and it seems perfect, no more vacuum leaks. ? I put new MSD wires on it, a new parts store cap and rotor, I will put new plugs in it as soon as I have time, but I did pull them when doing the compression test and they looked fine.

No hint of ping and runs smooth and sweet up to 4500 rpm then sputters badly (even free revving it in park). It recovers immediately when I shift. I used to shift at 5300 no problem, and accidentally let her spin up over 6000 once unintentionally.

The season is almost done here and I’ll be putting it in the garage for the winter with the intent of doing some work on it to be ready for spring. My question is this, where should I spend my time looking for this miss?

What spec does everyone use to set the reluctor gap to? Did my cheap shitty ignition box partially fail? I am leaning toward it being an ignition problem but I really don’t know.

Any thoughts would be greatly appreciated.


Cley
 
I would suspect the pickup coil in the dist worth a look all the right symptoms .
 
He put on new MSD wires. Maybe go back into the distributor and check that everything is secured, breaker plate is not loose. It could also be coil breaking down or as you said ignition module breaking down. Unfortunately it's trial and error when trouble shooting problems like this.
 
No hint of ping and runs smooth and sweet up to 4500 rpm then sputters badly (even free revving it in park). It recovers immediately when I shift. I used to shift at 5300 no problem, and accidentally let her spin up over 6000 once unintentionally.


What spec does everyone use to set the reluctor gap to?


Cley
I believe the factory service manuals list the reluctor gap at .008 set with a non-magnetic feeler gauge. [Brass)

What did you change since the last time it ran up to 6000 rpm's?
 
Another question I have is what is the best ignition box out there? I like the thought of the FBO. Has anyone used it?

Cley
 
I changed the fuel pump, the plug wires, the intake gaskets and I messed with the timing. That all took place after the miss started. Do you wreck anything if you set the gap with a regular feeler gauge? Cause I did set it with a regular feeler gauge. That was after the problem started too.

Cley
 
you kind of describe it like an electrical "break-up". Just off of what I read, I'd suspect electrical, and everything you changed would be suspect.
 
I changed the fuel pump, the plug wires, the intake gaskets and I messed with the timing. That all took place after the miss started. Do you wreck anything if you set the gap with a regular feeler gauge? Cause I did set it with a regular feeler gauge. That was after the problem started too.

Cley


yes you can sometimes mess up the pickup coil with a steel feeler it is recommend to use brass . the last pickup I put in was 19 bucks and fairly easy to do .
 
Yeah put on a Mopar orange electronic ignition box first if everything else checked out fine ...
 
yes you can sometimes mess up the pickup coil with a steel feeler it is recommend to use brass . the last pickup I put in was 19 bucks and fairly easy to do .

Maybe I'll start there. I know the first time I set that gap it was .008 with a steel feeler gauge. I since picked up a brass one.

Cley
 
Yeah put on a Mopar orange electronic ignition box first if everything else checked out fine ...

I heard some bad reviews on the Orange box. Not sure if that's where I want to go, but this parts store special will definitely be no better.

Cley
 
Do you run vacuum advance? If so disconnect and plug the vacuum line and try free revving it slowly in neutral and see if it goes away. I had a similar problem.
 
It could be rotor phasing. I had a rotor that was to tall and would arc to the top of the cap terminal instead of the side. See the burn marks in on the cap. Search msd rotor phasing video.

57E1442C-7B6A-4335-8B43-3D36C0080EDF.jpeg
 
I also haven’t heard of that regulator. Don’t run a cheap regulator. I run a big mechanical and a holley red pump together. Don’t like the included holley regulators. Red pump doesnt need reg. No issues.
 
You wrote ,"I used to shift at 5300 no problem, and accidentally let her spin up over 6000 once unintentionally."

Did the problems start after you went over 6K....if not what did you change on the engine?? If it ran fine at one time something had to change?? treblig
 
74 Plymouth Duster, 360, A-500, 8 ¼ w 3.23 sg. Running at 185 degrees (confirmed with good IR heat gun). 3/8” pick up in tank with -6 AN braided line between tank and fuel pump. New Carter HV fuel pump with Performance World regulator set to 6 psi. Fuel filter is perfectly clean. Holley 670 Street Avenger on an Edelbrock Performer 318/360 intake. Stock 1.88/160 J heads and unknown pistons (100PSI compression even on all cylinders when cold). Unknown cam, but definitely more duration than stock. Stock electronic ignition with cheap parts store ign. box with external ground jumper to case. I adjusted the reluctor gap to factory spec. Timing at 22 deg. btdc @ idle with total 34 deg. in at 2500 rpm. I messed with it for a quite a while and it runs best there. I just redid my intake gasket due to a bad vacuum leak and it seems perfect, no more vacuum leaks. ? I put new MSD wires on it, a new parts store cap and rotor, I will put new plugs in it as soon as I have time, but I did pull them when doing the compression test and they looked fine.

No hint of ping and runs smooth and sweet up to 4500 rpm then sputters badly (even free revving it in park). It recovers immediately when I shift. I used to shift at 5300 no problem, and accidentally let her spin up over 6000 once unintentionally.

The season is almost done here and I’ll be putting it in the garage for the winter with the intent of doing some work on it to be ready for spring. My question is this, where should I spend my time looking for this miss?

What spec does everyone use to set the reluctor gap to? Did my cheap shitty ignition box partially fail? I am leaning toward it being an ignition problem but I really don’t know.

Any thoughts would be greatly appreciated.


Cley

Hey Cley,
Just went through this myself. Possible Ignition box , mismatched coil and ballast resistor( It changes value as it heats up) or Coil is also a good suspect.
Hope this is of some help. Good luck with it.
 
Here's the ignition box I am currently using. Found out about it in Mopar Action. Big improvement over the new orange box I just installed that crapped out after 200miles. Price is pretty good as well.

  • 555-40805.jpg


Blue Ignition Control Unit 7,500 RPM
Part Number: 555-40805
made_in_usa.svg



JEGS Blue Ignition Control Unit 7,500 RPM $34.99


HiRev 7500® Ignition Control Unit
  • Modern Electronics with Mopar OEM Appearance
  • Comparable to Mopar Chrome Ignition Control Unit
  • 7,500 RPM
  • Made in USA
 
Couldn't it be fuel starvation???

It could, but I replaced the fuel pump with the Carter and confirmed 6 psi at the carb and it never changed the issue. I also checked the fuel filter. The sending unit and fuel line are all fairly new and all 3/8".

Do you run vacuum advance? If so disconnect and plug the vacuum line and try free revving it slowly in neutral and see if it goes away. I had a similar problem.

I do run vacuum advance. I'll disconnect it and try it.

It could be rotor phasing. I had a rotor that was to tall and would arc to the top of the cap terminal instead of the side. See the burn marks in on the cap. Search msd rotor phasing video.

View attachment 1715241891

That part looks ok, but I do see some blackening on the top of my rotor (the plastic below the center of the rotor). I'll look again.

I also haven’t heard of that regulator. Don’t run a cheap regulator. I run a big mechanical and a holley red pump together. Don’t like the included holley regulators. Red pump doesnt need reg. No issues.

That regulator was on it before the problem arose. You may be right though.

Cley
 
You wrote ,"I used to shift at 5300 no problem, and accidentally let her spin up over 6000 once unintentionally."

Did the problems start after you went over 6K....if not what did you change on the engine?? If it ran fine at one time something had to change?? treblig

It did happen after the rev over 6k. But not immediately after. Everything else I did was to try and correct the issue.

Here's the ignition box I am currently using. Found out about it in Mopar Action. Big improvement over the new orange box I just installed that crapped out after 200miles. Price is pretty good as well.



Blue Ignition Control Unit 7,500 RPM
Part Number: 555-40805
made_in_usa.svg



JEGS Blue Ignition Control Unit 7,500 RPM $34.99


HiRev 7500® Ignition Control Unit
  • Modern Electronics with Mopar OEM Appearance
  • Comparable to Mopar Chrome Ignition Control Unit
  • 7,500 RPM
  • Made in USA

Thanks, That is another ignition box I was considering. I was thinking about the FBO because of the rev limiter but they want you to buy their coil too.

Cley
 
If we eliminate ignition and carb issues, we have to consider valve issues, broken/weak v/springs, issues with keepers and retainers. Would need to remove v/covers to inspect.
 
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