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Author Topic:   Sparkplug Questions??????
Speed Racer X
Dirt Full Roller

Total posts: 61
posted March 30, 2003 10:35 PM
WE are running a set of double hump SBC heads. They require a 14MM, 13/16 hex, .375 reach, gasket type plug. Last year we ran "AC R43" and had good luck.
This year we put more compression (13:1) and inches (383)in the motor. We are now running a "NGK B8S"(gapped at .040 with a hot HEI), but they didn't last long before we got picked up a miss. I may be wrong, but I thing a new set of plugs will fix it.
The plugs came out with a light tan color(we are running race gas), they had been almost a white-gray but we jetted the carb up a couple of steps. When the car left the pits it was running good, but it picked up the miss about half way through hot laps. If it makes any difference the air temp was in the low 40's.
So before I go buy new plugs I would like to ask you guys some questions
The "NGK B8S" is a fairly cold plug, is it too cold, would a B7S or B6S be better? Was .040 too much gap? I've heard a lot of talk about "Autolite #303" or "Champion J8C". What brand and heat range plugs do you guys run? Thanks again for all the help!!!

dirtrace54
Dirt Forum Racer

Total posts: 91
posted March 30, 2003 11:03 PM
I have always been die hard to the good 'ol AC Delcos.

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racer17j
Dirt Forum Champ
Total posts: 1565
posted March 30, 2003 11:31 PM UIN: 54865418
same here ac r45ts. a couple things you might want to check is make sure your fuel line is'nt geting pinched and also make sure it's not hitting anything hot i had a miss one nite out of nowhere turned out to be the line from my fuel pump to the carb was rubbing on the bottom radiator hose and boiling the fuel before it had a chance to get to the carb

rico 08
Dirt Freak

Total posts: 372
posted March 31, 2003 12:39 PM
I have to agree with '54,GM recommends a R44 in their high performance motors on the older heads(flat gasket)and the R43 you we're running are a little cold,the NGK plug you are now using ,if i crossed it right comes out to a 41 heat range in an ac which is the coldest plug they make and will probably foul out at idle rather quickly,i'd switch back to the R43 as the coldest plug to run and maybe even a R44 to keep it from fouling.

DMA Racing
Dirt Forum Racer

Total posts: 82
posted March 31, 2003 03:32 PM
i use the 303's,on 461 heads 30 over flat top

15a
Dirt Full Roller

Total posts: 44
posted March 31, 2003 05:21 PM
383 Camel Hump Heads with 11.5(?)C/R. I use Autolite #85 gapped at .040 with the side electrode cut back like the racing series plugs.

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