DragStuff

after a few runs down the quarter mile, the spark plugs insulator started to turn yellowish green, i read the plug article but it really didnt tell ya a fix , other then saying from prolong idling, which it was'nt idling long, is the plug to hot ? ty

Sounds like you have a fungus growing in your fuel cell? Have you removed the foam from it?


lol - probably just the fuel you're using that's coloring the plug like that and it's probably a bit fat or cold plugs. What plug you using? What's the application?

plugs are the autolite 3933, 50/ 50 mix 93 octane and sunoco 110 . its a 451 cu in engine, total timing is 38,, it has a 830 cfm holley race carb on it,out of the box the jetting was 76 pri, and 76 sec with 6.5 power valves , i plugged the sec p/v and put 84 jets in, 76 in the pri, i did have 78 / 86 in there , at the track i went both ways on jetting to find the more i take jetting out the more mph and better et,, went from a 11.12 to a consistent 11.03 at 120.9mph . not complaining for that.. just the plugs looked different like a glaze, didnt have time to try even less jetting to try to hit 121mph, so it may want less as you say , ty

You're using a very cold plug for motor only, AR3933 (NGK-9) is a pretty cold plug and it's going to glaze over and foul like what you're seeing. You need something like a AR3935 which is like a NGK-7 or hotter if you're running motor only. Try that, it should make a big difference.

i got the 7s will it change the tune will i need to jet it back up ?

Probably not, but the weather is fixing to change soon cooling off. It just depends on how close you were earlier, but I would not expect the plug change to have much effect on the tune up other than it's not going to glaze the plugs so bad. It will put a bit more heat in the cyl, it "might" want a degree less timing but that's not certain.

also it has a 140hp shot fogger on it w/24 nos jets and 20 fuel jets,5.7 fuel pressure, taking 8 degrees out on hit ,, rarely is it used , is that plug ok to start with ,, the nos is probably used an 1/8th mile at a time , to steep a gear to make the 1/4.. thanks for the help john,,

You should probably drop down at least one step colder on the plug when you're going to be spraying it - Like to a -8 NGK.

It's not a big shot, and yeah in a pinch you could probably get away with the hotter plugs if you have enough timing out, but it's probably not a good idea to risk it.

Are you pulling 8 degrees from your base timing of 38? If so 30 degrees is too much timing for that 24 jet. Especially if your running low octane fuel. As john said you will want to drop down to a colder plug. We run -10 ngks on our .032 jet fogger or you could run 3932 autolites.

i actually do run a better mix then 50/50 when using the nitrous ,that was just this past weekend running on just motor,usually 8 gallons of 110 and 2 gallons of 93 ..