SPARK PLUGS-TUNING

Ok, back to all the experts. Where on the run do you think the sparkplugs get there burn pattern? Is in during the burnout? During the launch when the engine is working its hardest? Or on the last bit of the run when the Hi-Speeds are all open? If you have to pedal the car once, do you still read that set of plugs or are they now not reliable information tools? Sorry, I know that I just asked a bunch of questions at once. I would like your guys opinion please.

 

Come-on Will, or Bill A., Randy G. Doesn't anyone have an opinion?

 

Have made 1/8 mile passes on 1/4 mile tune up and plugs are clean than run full pass and plug show heat with and without hi speed

 

Some fond memories of Larry.....his great burgers that he would not serve "before their time".....and the "special" apron he had custom made that he would wear at his dnq party Sat. nights.....God Speed Larry.....

Mike and Janet Kosky

 

I think it all depends on the type of blower, and how good it is. With our roots, we also made some 1/8 mile passes, and found the plugs came out almost new. Same tuneup on a quarter mile pass burned most of the cad off.

 

Thanks for the replies. The reason for the post {isn't there always some reason} We ran the car 1/8 mile, Had to pedal the car, about 3/4 track, then back on the gas. I looked at the plugs, it was just coming down the electrode, not down on the base circle yet. So I changed main to 115, from a 110, and went up for the 2nd pass. We had to wait approx 40 mins during which time the sun went under. It was 60 and sunny, 1200 foot air, so the air got better by an unknown amount, and we made a nice pass, 4.34 @ 165mph. I looked the plugs over and we had burned 3 electrodes, all plugs were down a thread or so. I wanted to know if the air could change that much, or if lifting had fooled the plugs on the first run, so they weren't a reliable source for tuning off that run. Thereby making my decision to pull more fuel out, based on them, a wrong decision. I am going to flow the system again tonite, but we found nothing else wrong on teardown. So my theory is that lifting on the run, made those plugs a poor indicator of what was going on with the fuel. We got caught by the air changing and the 1st run plugs being off. Any opinions?

 

Sorry, for the long post guys. The engine is a 465 cu,inch KB600 solid Alum block, w/360 solid heads. 1471 Hi-helix. 25% over. 10.04 gallons on the fist run, 9.84 going into engine on the 2nd run. We were not getting any real temp in the motor also making me think it was still real fat.

 

Ken, it looks like you and Will agree, the plugs color on the big end of the track for the most part. That supports what our car did, when I pedaled it at 3/4 track, it got fat again, and never completed coloring the plugs on the first run.

 

Are you saying you are burning 10 gallons of fuel in an 1/8th mile pass?

 

Will, NGK 8's. 19 thousand on the gap. I reflowed everything last nite for a bit. I found out I was not putting in the engine {fuel amount}what I thought I was. I had some wrong info in my jetsize program, so it was giving me wrong readings back. Will, I follow along with what you are saying about the lean spot. That makes sense, but our engine didn't show that at all. As I stated, the plugs were not hardly colored. That is the part I really don't understand. It has to have something to do with pedaling the car on the run. One thing that was interesting last nite, with the pump flowing at 8000, shutting the injector blades {like you pedaled it} the pressure drops like a rock for a second. Perhaps that reset my Hi-speed, keeping the plugs from showing lean on that run. I am sorry these posts are soo long. This is a really interesting subject {fuel system} for me.

Rapid

 

Danny, he is referring to GPM, the flow rating on fuel. you take the amount the pump flows and plug your jetsize into a formula, and it gives you the gpm your motor will see.

Will is correct.

Rapid

 

I was going to say check your oil pan for the rest of that fuel!

 

Just my oppinion but I think that because you lifted and the fact you are only running an 1/8 mile track the motor probably didn't get a chance to generate any heat but there a lot of factors we are all guessing at we don't know how long you were out the throttle for or how low the engine rpms got to. Also another thing to rember is that jetsize is just a theoretical number with out a flow meter there is no real way to tell how much your pump is really flowing durring the run. Also the weather change could have been a big factor as well. It is a very tuff call to say what exactlly happened but one sugestion is buy a data recorder with at least egts and that will help take a lot of the guess work out of it and show you how even the most minor change can be not so minor.

 

You can definitely see heat in my plugs after an 1/8th mile pass.

 

WOW! 9.84 gpm? My 400in Chevy was at 11gpm on alcohol at 42lbs boost(PSI)and probably would have melted if I hadn't had to lift at the 1/8!
Really good October air at MIR on a test day. I've not run nitro, but that doesn't sound like much fuel to me!
CMD