yes i know... the numbers should be the same.. a friend helped me do these last time at SIR... i took them out.. he gapped them.. i put them in... i guess i should have checked them no wonder it ran like crap #1 .053 #2 .051 #3 .053 #4 .051 #5 .063 #6 .051 #7 .050 #8 .052 they are all kinda close to each other except #5.. .063 ???? WOW now the question is.. what gap should i go with here is the basic setup 9.5:1 pitsons bored .040 477 intake 484 exhaust cam 4 angle valve job 120# springs edelbrock performer intake edelbrock 600 carb MSD dizzy MSD 6a box MSd blaster SS coil MSD 8.8 MM Super Conductor wires the best i ran was a 14.5 at 95 last december.... the last time out.. november i think... i ran 15.1 at 93.. after these plugs were put in.. i think the gap was .044 but i dont remember... my friend said that .050 would be better because i had the ignition that could handle it.. but turns out. it wasnt better... thanks for any help... i am buying new plugs tomorrow.. and i suppose i should get a good plug and gap it...
Increased gap increases the chance of misfiring. Decreasing the gap sometimes will allow fuel/oil to bridge the gap and cause a misfire, but that usually only happens at really small gaps, less than .020". I like around .035". On a high-boost turbocharged engine or nitrous engine, I like them around .025-.030. Depends on the ignition too. A GOOD coil with a GOOD ignition box will allow you to open 'em up quite a bit. In your case, I'd stay between .035-.045". That's a good starting point for just about any combination. Gaps aren't critical until you get to a certain point where the ignition simply will not jump the wide gap under a lot of cylinder pressure. (Did you know) at the ~1000' foot mark, a nitro burning Top fuel car is self-sustaining? The spark plugs are completely consumed. Only way to shut 'em down is to shut off the fuel. Once cylinder/combustion temps are at a certain point, the load on the ignition system is reduced drastically because it no longer requires as much energy to ignite the compressed mixture.
A lot of the articles I have read recommend a wider than stock gap with the MSD ignition or equivalent. I would suggest .040" to start. Buy a second set of plugs and increase the gap by .005". If performance improves, gap the next trial set at .050". Stop when the car fails to respond in a positive direction. We run the NGK plugs our 9.00:1 compression 6 cyl race motor at .045" with a 6AL ignition.
well i had champion v63c plugs.. and i was told that was too hot a plug.. and i looked at them.. they are black.. but i was also running 110 octane int he engine at the time... then i went to motorcraft plugs.. and they are all gapped at .040 and look white... then i went with autolites... the ones in there now... they are gapped as shown above.. and they are real white.. i am taking all the plugs to SIR satruday morning and have don look at the them.. when i ran the 14.5 i had the v63c plugs in there with race gas.. i have heard about the NGK.. any particular part number to get? all the plugs are out right now.. so i am open.. i was thinking of runnint .040 and a nice hot plug.. the tank is almost dry.. so i am thinking 3 gallons of 91 to get me to the track and then i will get 5 gallons of race gas. see how that runs... people tell me i dont need race gas.. but i can feel the difference..
so any compression up to 10.5 should be the 50 -60 gap... wow... i sent MSD an email asking them where to start with my setup... hopefully i get an email soon
hey blown... looked at your pic and realized... if that is your car doing that, i am curious... did it hurt... looks like the car doesnt have more than 1 tire hitting the ground.. i bet you are greatful for gravity... or you might have been in space..
best way on this is trial and error/experimentation. start around .045 and make a run. up the gap .005 and make another run. see how it likes it. if it likes it,go up another .005 and make another run. you should reach a point where it doesnt run quicker or slows up or maybe stumbles a bit. go back to the last gap.dont forget to allow for weather changes whe judgeing effects. as a rule of thumb, larger gap helps bottom end and economy. smaller gap helps at higher rpm. find the happy medium which should be the largest gap which doesnt hurt the top end power. dont forget that plug heat range, fuel mixture ratio, and timing advance can all have an effect on which gap performs best.
engine gets hot... headers hot... hard to take plugs out and regap that often at the track... but yeah.. i am going to get some new plugs.. gap them at .042 and try that out tomorrow at the track.. and take some notes... i just hope i get back into the 14 range..
Yep, trial and error to find your combination. With my Mallory HyFire box and a small shot of nitrous I have my plugs gapped at .054".
this is from MSD them selves.. saw this AFTER i gapped to .040 and put in the plugs Sir, We do not have a preference to plug brand, brand of choice. We do however recommend using one to two steps colder then stock and we generally recommend opening the plug gap up .010-.020 over what you normally run with a maximum of .065. The box will fire much larger then this but the energy required is hard on the caps, rotors, wires and plugs. We recommend using a standard style electrode non "HYPE" i.e. special coatings metals, electrode designs etc. Use a standard basic plug. Thanks, MSD tech i bought some accel plugs gapped to .040 and will run this tomorrow and see waht happens
ko.. i just went and "test" drove the maverick to the gas station and back.. all i can say is OMG. i cant wait until the morning.... im gonna make a new time i think... we shall see
