Help What plugs / gap to get for 308?

Unknown
Unknown
edited November -1 in HUDSON
I've replaced the points and condensor. Cap, rotor and wires were replaced a few years ago. I gapped the points to .020 and am getting spark.



Interestingly enough, only 4 out of 6 plugs fire. And it gets more interesting. If I pull one of the wires a little distance from a plug, that plug starts to fire.



Amaxingly, the 308 runs pretty strong on only 4. :-)



What plugs do you guys recommend, and what gap? Maybe replacing the plugs will get me 6 for 6.



Thanks;

-Chris

Comments

  • Unknown
    Unknown
    The plugs aren't that old either. Could mis-gapping the points cause only some of the plugs to fire? Maybe my timing's off?



    hmmm..
  • dwardo99
    dwardo99 Expert Adviser
    This is an indication of plugs that are fouled or otherwise defective. You should replace the offending plugs at least. Timing shouldn't do that. A condenser that's on it's way out might but the indication is that the problem is local to the two plugs. The wires for those plugs might be defective also. If there is enough slack in the wires, try switching plug wires and see if the problem moves to different cylinders.
  • Unknown
    Unknown
    .020 is recommended setting, last post was dead on obout fouling , usually do to excess oil/fuel in cylinder. Oil most of the time. When a condenser is shot it is dead, one that is going downhill will cause point builtup on one side as it starts to lose it capacitance. Open the plug clearance to .035 and try that also make sure you have the proper heat range plugs. They may be too cold for your engine, despite what the book says to use. The trick about keeping the wire end away from the plug is an old trick used when engines were shot.
  • Geoff
    Geoff Senior Contributor
    Way back in the "olden days" there used to marketed a divice called a "Spark intensifier". This was basically a pair of contacts about 1/8 of an inch apart, which was sited in main high tension feed wire from the coil to the distributor. what happens when there is a gap, or dirty contacts, is the coil voltage has to build up to a higher potential to jump the gap. this is of course what is happening when you hold the wire a distance from the plug. Not a good idea of course, as it will eventually lead to coil failure. Getting back to your problem you need to check the cleanliness of the plugs, and perhaps go to a hotter plug. If there is a tendency to oil up, you will of course eventually have to face up to that, but going to say H12 in place of H10 may do the trick. Good luck,

    Geoff.
  • Unknown
    Unknown
    I USE CHAMPION H 10c AND GAP AT 32 THOUSANDS. JUST GOT 27.55 mpg with this set up in 308 on the Laughlin economy run, BILL ALBRIGHT
  • Unknown
    Unknown
    I still use the Champion H-11 but the H10-C and H-12 are still available. If you get spark when moving the wires on the cylinders in question, maybe you have a problem with those wires. It would be unusual for only the distributor lobes for cylinders 4 & 6 to be worn.
  • Unknown
    Unknown
    Dave53-7C wrote:
    I still use the Champion H-11 but the H10-C and H-12 are still available. If you get spark when moving the wires on the cylinders in question, maybe you have a problem with those wires. It would be unusual for only the distributor lobes for cylinders 4 & 6 to be worn.



    It looks like 2 plugs were dead. I replaced them all and she fired up great. I used a timing light to see who was firing and who wasn't.



    Now, why did the plugs fail? The plugs were relatively new, but I made a few changes to the ignition system.



    1. I installed a Pertronix Flamethrower "high performance coil".

    2. I ran it without a resistor for a while. The net resistance for the coil was 1.5 ohms. This may have weakened the plugs...?

    3 I installed a resistor, bringing the value to about 3 ohms.



    After a while, I noticed the problem.



    Also, the plugs are dark, carbonized. Not sure if this is a problem. No oil, and no "stuff" shorting out the gap.



    Maybe the coil with no ballast resistor killed 2 of the 6 plugs?



    I'll see if the new set dies.



    Is there a "high performance" plug I should be using?



    -Chris
  • Unknown
    Unknown
    Lots of carbon? If I remember right, that means your either running very rich or your ignition system isn't working at it's best. Might want to check over your coil and other connections to make sure your getting a good strong spark.
  • Unknown
    Unknown
    usgrant7 wrote:
    It looks like 2 plugs were dead. I replaced them all and she fired up great. I used a timing light to see who was firing and who wasn't.



    Now, why did the plugs fail? The plugs were relatively new, but I made a few changes to the ignition system.



    1. I installed a Pertronix Flamethrower "high performance coil".

    2. I ran it without a resistor for a while. The net resistance for the coil was

    1.5 ohms. This may have weakened the plugs...?

    3 I installed a resistor, bringing the value to about 3 ohms.



    After a while, I noticed the problem.



    Also, the plugs are dark, carbonized. Not sure if this is a problem. No oil, and no "stuff" shorting out the gap.



    Maybe the coil with no ballast resistor killed 2 of the 6 plugs?



    I'll see if the new set dies.



    Is there a "high performance" plug I should be using?



    -Chris



    1. Plugs usually don't fail unless physically damaged or they are pushed

    beyond design limitations. They do however wear out.

    2. The resistance of a stock 6v coil should range between 2K to 20K.

    3. Sounds like you have a collision of technologies happening. Personally, I

    see no need to use so called "high performance" plugs.

    4. Have you checked the resistance of the plug wires?

    5. Wasn't there a recent discussion on the forum about ballust resistors?

    6. How is it that you verified that individual plugs were firing by using a

    timing light?
  • Unknown
    Unknown
    I think you have already found your problem.
  • dwardo99
    dwardo99 Expert Adviser
    Those of us who fool with old motorcycles know that an engine with a marginal ignition system or that is running rich or burning some oil will foul a plug to the point that it won't work pretty quickly. Sometimes you can clean these plugs but sometimes not. If your ignition system is up to snuff and your engine is in decent condition, just replacing the plugs should solve the problem. If you have plug problems again soon, look for a cause other than plugs.
  • Unknown
    Unknown
    Dave53-7C wrote:
    1. Plugs usually don't fail unless physically damaged or they are pushed

    beyond design limitations. They do however wear out.

    2. The resistance of a stock 6v coil should range between 2K to 20K.

    3. Sounds like you have a collision of technologies happening. Personally, I

    see no need to use so called "high performance" plugs.

    4. Have you checked the resistance of the plug wires?

    5. Wasn't there a recent discussion on the forum about ballust resistors?

    6. How is it that you verified that individual plugs were firing by using a

    timing light?





    Hmm. Additional information.



    I converted to 12v, neg ground, and got a 12 v coil. The plugs are fairly new.



    I hooked up a timing light to each plug, one at a time. If it strobed I assumed the plug was working. if it didn't strobe, I assumed it didnt. To verify, I pulled the wires on the plugs that didn't strobe and the engine did not run any differently. However, if I held the wire just off the top of the plug (not quite plugging it in), I could hear a tapping and the engine sped up a bit.



    When those 2 plugs were replaced, the engine ran a lot stronger. I of course replaced all 6 after the experiment was done.



    The entire ignitioin system is new, wires, points, cond, cap, rotor, plugs. I havn't driven the car much in the past 2 years. Got it back from the body shop 2 months ago and have put about 30 miles on it. Maybe I'll blow out the carbon by driving it.



    Here she is:



    http://moltar.chrishull.com/pics/Hudson24Sept2006/frontwithvisor.jpg



    Unless I'm really forgetting something, the resistance accross the supply for a 12v coil should be 3 - 4 ohms. For "racing conditions" 1.5 (according to Pertronix). I ran at 1.5 for a little while and am wondering if I killed the plugs thru over voltage. I am now running at about 3ohms using a ballast resistor.



    Thanks for the assist;

    -Chris
  • Unknown
    Unknown
    dwardo99 wrote:
    Those of us who fool with old motorcycles know that an engine with a marginal ignition system or that is running rich or burning some oil will foul a plug to the point that it won't work pretty quickly. Sometimes you can clean these plugs but sometimes not. If your ignition system is up to snuff and your engine is in decent condition, just replacing the plugs should solve the problem. If you have plug problems again soon, look for a cause other than plugs.



    I have some blow-by taking place. I wonder if oil got up inside the plugs.



    Wouldn't I see that? I'd think the plug gap would be filled with crud. All I see is a black coating.



    The 2 plugs failed shortly after I topped off the oil. That's got me thinking.



    I'll run for a while and see what happens.



    -Chris
  • Unknown
    Unknown
    Figured that is what you would find. Now open up the gap to .035 and see what that does. Good luck
  • Unknown
    Unknown
    Chris,



    If you're having a problem with plug fouling, have you thought about using hotter plugs? BTW, your car looks awesome!
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