Reply With QuoteRR, I've never run colder than 10's even at 36 lbs of boost. You might try .020 gap if you want to run the 11's.
What heat range would you guys recommend for my 621" blower motor? I have been using the NGK-9's when running with 91 octane gas at around 8-9 lbs. boost and the motor seems to run fine. When I put in race gas and bump the boost up to 14 or so, I changed to the NGK-11 colder plug for the 400 hp nitrous hit. I notice now that the motor is missing under WOT conditions with the higher boost set up. I called Larry Peto who told me that he thinks the reason is that the -11 plug is too cold and that may be what's causing the miss. I also have some -10 plugs that I may try the next high boost run to see if that helps eliminate the miss. Any thoughts?
Keith
RR, I've never run colder than 10's even at 36 lbs of boost. You might try .020 gap if you want to run the 11's.
Thanks HH. The 10's ought to be fine for me even with the nitrous if you are able to run them with 36 lbs of boost. Is that on alcohol?
Is that on alcohol?
I would certainly hope so, unless you are running 30 deg ambient air temp!!!
Autolite makes a race plug with a cut back electrode. I would try them on a one or two step colder plug.You did not include any info on your ignition system.You may be exceeding the capacity of your current system.
Autolite makes a race plug with a cut back electrode. I would try them on a one or two step colder plug.You did not include any info on your ignition system.You may be exceeding the capacity of your current system.
Thanks DEL. I have a MSD 6AL ignition fired by a MSD crank trigger. I was wondering about the 6AL's ability to fire the -11 cold plugs.I have enough race gas left for one or two more passes so will crank up the boost again this weekend (no nitrous) and replace the -11 plugs with the -9's and see if the miss goes away.
I notice now that the motor is missing under WOT conditions with the higher boost set up.
Sounds like a lean condition. Be careful you don't hurt the motor. How do the plugs look?
I didn't get a good plug reading because I didn't shut it off quickly enough after the run and it idles so fat that it loaded up the plugs so I couldn't get a good reading. I will do a fast shut down after a run this weekend and try to get a good plug reading. I didn't think it would be running lean because the density altitude during the dyno session was 4,000' and it was fat then. The air quality last weekend where I ran it was 2,400' so I didn't think I would need to rejet but you may be right. It definately deserves a good plug check. :idea: Thanks.
I'd run the -10's gapped .025" Worked well on my old 632" NA occasinally spayed motor. That was with an MSD digital 7 programable box. Ran -9's otherwise same gap. Is your fuel system up for 14# boost and 400hp NOS shot? How much timing are you pulling out?
Thanks CJ. It's missing on the high boost with the -11's even before I hit the NOS. I have a low fuel pressure alarm and it's not going off so I think my fuel system is okay. I do have a separate fuel tank and pump just for the NOS fuel. I have the MSD auto retard box and it's currently set up with a 10 degree retard chip, so it drops from 34 to 24 when I hit the button. I tried 30 degrees and retarded it to 20 but I still got the miss so I don't think it's timing related. It could be the plug gap too as I may have it gapped to wide at .035". I will try a high boost only run this weekend with the -9 plugs. If the miss goes away, I will put the -10's in with a .025" gap and give that a try with the juice the next time out after I refill the bottle.
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