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Correct spark plug gap on Ford 302 with HEI?

Discussion in 'The Hokey Ass Message Board' started by Berdoo John, Jun 21, 2005.

  1. Berdoo John
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    Berdoo John Member

    This is a freshly rebuilt 70's(?) 302 Ford. 700 miles on car (Model A). Everything on it was brand new, including HEI distibutor from Speedway motors and Comp Cam High Energy kit 218 (installed by engine builder). Plug wires that were installed initially were 7mm. I installed a fairly cheap set of 8mm wires on Friday after finding out the 7mm that were installed were inadequate for the HEI. Firing order has been checked several times and is correct. Champion plugs are gapped @ .044. This is third set of plugs I have tried. Motor smoothed out somewhat with the fresh plugs I put in Sunday but my symptons still exist.... Motor has a miss, can hear the valves ticking (they were snugged up in the beginning), and I have hesitation when I push on the pedal, even on the freeway, let off the gas to brake or coast, and push the gas pedal, hesitation.

    According to my book .044 is the correct mid '70s Ford V8 gap with electronic ignition. In late 70s/early 80s gap opens to .050.

    So as distributor efficiency/quality improves does the gap need to be larger?
    From what I have read on online descriptions for HEI distributors they say they allow for gaps of .050-.055.

    Should I open mine up some? Any suggestions? Thanks in advance. John
  2. Mojo
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    Mojo Member

    maybe the tempature range is off a bit? Have you tried hotter or cooler plugs? I run a MSD box, my engine really woke up when I opened the plugs up to 60. I also trimmed the electrode back over the center of the plug. That helped a bit, but they tend to need to be cleaned more often. Not really fouling, they're just more sensitive to crap on them.
  3. Berdoo John
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    Berdoo John Member

    No I haven't tried that. I just get whatever AutoZones 'puter says for mid/late 70's 302.
  4. Berdoo John
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    Berdoo John Member

    Bttt.

    In addition, can someone school me on how to determine if a motor needs a hotter or cooler plug?

    TIA, John.
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  5. mikeyboy
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    mikeyboy Member

    step one...take the champion plugs and throw them as far as you can
    step two...get a set of NGK V power plugs (78 granada 302)
    step three... set gap @ .050
    step four...get a GOOD set of wires.
    step five.....drink Beer :D
    bur seriously folks.....check the coil & see if it is internal resistance unit or if it is designed for use with a resistor, & check voltage at the coil.
    how much timing do you have in the motor ?
  6. AnimalAin
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    AnimalAin Member

    Your idiot pal here had some problems with running incompatible coils on electronic ignition (351W). Used the wrong one, run ok for a while, then run bad for a while, then won't run at all. Got the right one, and the damn thing goes like a train.
  7. Derek
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    Derek Member

    You've got an HEI in your ford? I am only asking because HEI is a GM term for their electronic ingnition systems (High Energy Ignition). I know that they are made for other applications though also. I am only askin becuse if you have an HEI ignition that would mean you have an in cap coil, is this correct? In my experiences an HEI ingnition works best somewhere between .050 and .060, so that's where I would start. Also, i would shit can the Champions too. Not a fan of their plugs, NGK are good, I prefer Autolites in V8 apllications though. That is just personal preference though, I run NGK's in all of my motorcycles and most of my 4bangers. As far as finding out about heat range, it's always been hit and miss for me. I know ther eis a formula somewhere, but I have never used it. If my ride seems to be runnin' lean when everything is tuned right, I go a step colder, and if it seems to run too rich, well do the opposite. Good luck and keep us posted.
  8. wllm500
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    wllm500 Member

    ok.. this is just a theory as im having a similar problem when i went to the DUI ignition system with my ford... and again... i have not tried it yet, it is still sitting in the garage since paso.

    to me, the hesitation could coming from the fact that with the new and improved spark, the engine is burning things much faster, and thus causing a lean condition... and that could be the hesitation. at least that is what mine is acting like. i have not investigated if it would be air/fuel ratio or accelerator pump shooters, cam, etc.

    just an idea?
  9. wllm500
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    wllm500 Member

    sorry... i mean maybe look at carb dial in rather than plugs ??
  10. Berdoo John
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    Berdoo John Member

  11. 286merc
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    286merc Member

    Im another one voting for trashing the Champs. Ive also had some Autolites bad right out of the box. Went with NGK in just about everything I own or build. I use platinums in my 351W truck; starts instantly in any weather and not a hint of problems.

    Grab a spray bottle of water and check for vacuum leaks everywhere; check condition of wires (measure resistance) and be sure not sitting on exhaust. Cheap wires from AZ are pure shit. Go thru timing, be sure you dont have slop in timing chain or dizzy.
  12. Mojo
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    Mojo Member

    platinum plugs are great, I ran them for a while, I hardly ever had to clean them and they always worked right. The MSD box was making them burn a little too hot, so I was getting spark ping during the summer, so I switched to normal plugs. Platinum plugs are worth the money...
  13. RoadKat
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    RoadKat Member

    U can read plugs by the burn color on the electrode. Fords seem to be happy with a dark tan color. And the hei will like a wide plug gap. Ford dis also do better wit a little recurve, but not too wild.
  14. BigChief
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    BigChief Member

  15. Rustamino
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    Rustamino Member

    That's very cool, thanks for the link! I had no idea something like this was even being made. I have a freind who's been having a lot of trouble with his ignition setup in his '55 Crown Vic with a 302, this might be just the thing!
  16. Derek
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    Derek Member

    Yep, I woudl definitely open it up from the .044. Some of the earlier HEI's called for that stoc, but average was more like .050 or so and I've seen stock gaps with an HEI as high as .060 or so. The recurve might be a good idea also depending on what you got from petronix. If it's all gm type on the base plate also that's pretty easy too. nothing more than a spring kit.
  17. hjason
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    hjason Member

    Hello, i'm having a problem with my truck..
    I have a 1994 f-150 2wd with a 302 EFI.
    It has been running really bad lately.

    I just checked the plugs they seem normal.
    Except a few, that were deformed like got to hot on the prcelin.
    The gaps went from where i gapped them at to over 60.
    I have no idea how that happens.

    But anyways the truck has been running weird, like it's getting to much fiel or not enough.
    I have to kick in the passing gear to get it to go.
    When at idle it runs ruff, and when taking off it runs like it wants to die.
    At speed it bucks every so often.

    I have tried to find out what it is, but i haven't had any sucess.
    I don't have the money to take it somehwere to get it fixed.
    Which i have a feeling it will cost an arm and a leg.

    If any of you could help me out with this? i would be greatful.
    Thanks
  18. GMC BUBBA
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    GMC BUBBA Member

    :eek:Spark plug gap should go with engine design and combustion chamber design , NOT the ignition system.

    I would suggest using the gap that orginally was spec-ed for the engine.

    Changing the ignition system doesnt change the engines spark requirements.
    HEI was developed for lean air fuel and epa 50,000 mile emissions requirements. Low compression and lean air made the mixture very hard to fire and keep ignited.
    One of the better ignition modules on the amrket with variable dwell control and current limiting circuits.
    We use this controller in many other igntions .

    Just something to think about.:D
  19. Francisco Plumbero
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    Francisco Plumbero Member

    Well shit Bubba, you sure killed this thread. How do you feel about the NGK platinums, I use the Champions myself, I clean the once a month.
  20. Fiddytree
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    Fiddytree Member

    NGK, .050, 650 Holley, alum heads, HEI from Performance Dist. NO platinum in carb motors.

    YMMV. (Your mileage may vary.)
  21. GMC BUBBA
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    GMC BUBBA Member

    Didnt mean to kill a thread but plugs are the most mis understood part of the ignition.
    So lets look at it a little closer.
    A spark plugs heat range ( nothing to do with water temp) is determined by the length and size of the center insulator and the actual distance the heat has to travel to get to a cooler surface. In the sixtys this was a bigger problem than it is today. If the engine was going to be ran wot you needed one plug and it was going to be in town driving all the time it required another plug.
    The big breakthru came when the plug makers made a extended tip plug and allowed the plugs electrode to hang in the combustion chamber a bit more. This allowed the plug to actually be different heats ranges as the air flow when ran faster was more air and cooler temp the plug acted as a colder plug ( highway), then when driven in town the air temp was hotter and allowed the plug to be hotter. I had read that the plug could ( extended tip) make up for 5-6 heat ranges a couple up and a couple down. Lets assume that worked for many years.
    Now lets discuss the aftermarket a little bit.
    No one makes a bad spark plug , these companies have been in bussiness for many years and will continue to do so. They do however make a incorrect range for a given application etc. Now lets use a story to explain what happens from time to time. ( a true story)
    I was a fleet mechanic for a fleet and we had new trucks that just eat spark plugs , needing to change them more than often. These trucks were bought without a bed and we had the beds installed as well as anew rear axle changing the gear ratios for in town use as they never were driven out on the highways...
    At someones suggestion we changed the spark plugs to another brand of plugs and WOW the problem was fixed!!! It just happended that the other plug was the correct plug for the new application ( we created) and ran very well from then on.
    In reality the correct factory plug ( in the correct heat range ) would have done the same thing. I am sure that my co workers and me for years used the aftermarket spark plug thinking the orginal oem plugs were junk. When we step away from the oem plugs we do exactly that , if we needed a change then if may fix the problem or make it worse, really has nothing to do with the actual brand.
    As a automotive instructor for many years i dont ever wish to kill a thread , i just want everyone to think it out....
    Last edited: Aug 29, 2010
  22. Norfab
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    Norfab Member

    Motor has a miss, can hear the valves ticking (they were snugged up in the beginning),

    May not be ignition. If the valves are out of adjusment after 700 miles, something else is going on.
  23. Francisco Plumbero
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    Francisco Plumbero Member

    Bubba, Thank You. I didn't mean that you killed the thread so to speak. When a man who does this for a living and has years of experience in the field gives his personal response that kills all the speculation and mystery, and rightly so. I always hope to learn something on here and did from your response, again thank you.
  24. GMC BUBBA
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    GMC BUBBA Member


    Thanks for the comments.....
  25. plymouth1952
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    plymouth1952 Member

    with this in mind I am using a 77 350 olds in my 60 olds I cant use the HEI due to it riding 1/2 under the wiper motor I have to use the older stock points dist now what should I gap the plugs for ? even with a Patronix set up ? thanks
  26. GMC BUBBA
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    GMC BUBBA Member

    .035 should work fine.
  27. 40fordtudor
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    40fordtudor Member

    good formula---i gap at .055 and she runs like a scalded dog. windsor jr. heads is the only difference.
  28. 55yoyo
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    Delray South Florida

    55yoyo Member

    Hey there,Im not gapping my plugs yet but sooon!!I'm looking for some help,going to put on a carb and points ingnition set up on a mid 80's 302 from a Bronco that had EFI into my 55 Ford.Not a race or speed car at all,just a fun car for cruzzzin.Bosch??Accell??MSD??Not sure if the boys at the local Auto stores know whats going on,I'm new to it all and need some direction.Thanks for any help.
  29. pcterm2
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    pcterm2 Member



    what about the valves ticking-hello?:eek: just saying

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