spark plugs for GT-40X heads

meknized · 08-19-2006, 07:24 PM

Hello,

I have a question on some spark plugs. I have the GT-40X heads on a 331. I was just changing the spark plugs which are autolite 764's. It has been at least 3 years since I have changed them. One of the plugs in back on cylinder 4 was a champion RS12YC and the other 7 were the 764's. I remember after pulling them that I had broken one of the plugs and that is why I must have put the champion back in. The problem is, is that the autolites have about 3/8 long thread section that goes into the head and the champion have 5/8. I guess I didn't compare them when I had them out. Are the autolites I have been running not reaching in all the way into the combustion chamber? So I need to know if I need a long treaded plug. I can't get my head down far enough to see.

Coupe50h · 08-19-2006, 10:20 PM

I think the champions and motorcraft are that way, i run the 764's on my iron's, and I think i noticed shorter thread on the autolite then the motorcrafts, I dont have any experience with the 40x heads, but I would't worry, either plug should work fine.
Hey meknized, your combo sounds badazz for a street car, is your e.t. on street tires, or stickies?
sounds like a similar combo im looking to build someday, you ought to get high 11's 110+ out of that though.

meknized · 08-22-2006, 08:42 PM

Hey,

Thanks for the response. What threw me was that the autolites had a shorter thread then the champions. But the electrode depth was the same. Oh well had to make sure.

My current best time is a 12.02 @ 112 60ft. 1.7. That was on M/T 10X26 slicks. 12.5 @ 109 on radials. My launch was roughly at 3500 rpm or so. I know I can hit an 11. That particular day there was a 12 mph head wind, not saying that I would have hit an 11 but I think I could have maybe knocked out that last .03 of a second without it. I'm still learning to launch on the slicks and could launch harder, but I don't get out to the strip as much as I would like to practice. Always fun though!!

There is some pictures of my car on www.haiokuracing.com during a imports vs domestics at our local track. click on past events at the bottom on sun May 14th. I'm the blue and silver GT.

Coupe50h · 08-22-2006, 10:51 PM

Nice man, id like to see a video run of your car, That combo, with a tremec especially, should see high 1.5, or low 1.6 60's with a hard launch....later

08-19-2006, 07:24 PM	#1
meknized fox fanatic Join Date: Jul 2004 Location: wichita Ks. Posts: 61	spark plugs for GT-40X heads Hello, I have a question on some spark plugs. I have the GT-40X heads on a 331. I was just changing the spark plugs which are autolite 764's. It has been at least 3 years since I have changed them. One of the plugs in back on cylinder 4 was a champion RS12YC and the other 7 were the 764's. I remember after pulling them that I had broken one of the plugs and that is why I must have put the champion back in. The problem is, is that the autolites have about 3/8 long thread section that goes into the head and the champion have 5/8. I guess I didn't compare them when I had them out. Are the autolites I have been running not reaching in all the way into the combustion chamber? So I need to know if I need a long treaded plug. I can't get my head down far enough to see. __________________ meknized Blue/silver 89 GT, Coast 331, ported GT-40x heads, X cam, cobra intake, 70mm TB, 75mm bullet, mac intake, 24lb inj, 255 lph fuel pump, accufab regulator, pulleys, MSD coil, 6AL, 300+ wires, Tremec 5 spd. pro 5.0 shifter, FMS drive shaft, headers, X-pipe, flowmasters, auburn pro series posi. moser 31s axles,3:73s, etc. Best ET 12.02@112.5 a pic A vid of a run:http://www.youtube.com/watch?v=l9JMcErxML8

08-19-2006, 10:20 PM	#2
Coupe50h Registered Member Join Date: Aug 2002 Location: SanAntonio, Tx Posts: 957	Re: spark plugs for GT-40X heads I think the champions and motorcraft are that way, i run the 764's on my iron's, and I think i noticed shorter thread on the autolite then the motorcrafts, I dont have any experience with the 40x heads, but I would't worry, either plug should work fine. Hey meknized, your combo sounds badazz for a street car, is your e.t. on street tires, or stickies? sounds like a similar combo im looking to build someday, you ought to get high 11's 110+ out of that though. __________________ X-Texas highway patrol ssp 1990 coupe - exploder Gt-40 iron heads, Explorer intake, 19 lber's. E-cam. crane 1.7 rollers. 190fp. 75mm maf. 65mm tb, tubular subframe connectors, mac cai, Asp crank pulley, T-5, king cobra clutch, flowtech 1-5/8 unequals, mac X-pipe Frpp driveshaft, lakewood Lca's. race weight 3,160 12.69 @ 107.35, 1.71 60' 26x8.5 drag's 3.90 gear 13.20 @ 106.91 - 235/60/15 firestones 2.3 60' 3.27 gear

08-22-2006, 08:42 PM	#3
meknized fox fanatic Join Date: Jul 2004 Location: wichita Ks. Posts: 61	Re: spark plugs for GT-40X heads Hey, Thanks for the response. What threw me was that the autolites had a shorter thread then the champions. But the electrode depth was the same. Oh well had to make sure. My current best time is a 12.02 @ 112 60ft. 1.7. That was on M/T 10X26 slicks. 12.5 @ 109 on radials. My launch was roughly at 3500 rpm or so. I know I can hit an 11. That particular day there was a 12 mph head wind, not saying that I would have hit an 11 but I think I could have maybe knocked out that last .03 of a second without it. I'm still learning to launch on the slicks and could launch harder, but I don't get out to the strip as much as I would like to practice. Always fun though!! There is some pictures of my car on www.haiokuracing.com during a imports vs domestics at our local track. click on past events at the bottom on sun May 14th. I'm the blue and silver GT. __________________ meknized Blue/silver 89 GT, Coast 331, ported GT-40x heads, X cam, cobra intake, 70mm TB, 75mm bullet, mac intake, 24lb inj, 255 lph fuel pump, accufab regulator, pulleys, MSD coil, 6AL, 300+ wires, Tremec 5 spd. pro 5.0 shifter, FMS drive shaft, headers, X-pipe, flowmasters, auburn pro series posi. moser 31s axles,3:73s, etc. Best ET 12.02@112.5 a pic A vid of a run:http://www.youtube.com/watch?v=l9JMcErxML8

08-22-2006, 10:51 PM	#4
Coupe50h Registered Member Join Date: Aug 2002 Location: SanAntonio, Tx Posts: 957	Re: spark plugs for GT-40X heads Nice man, id like to see a video run of your car, That combo, with a tremec especially, should see high 1.5, or low 1.6 60's with a hard launch....later __________________ X-Texas highway patrol ssp 1990 coupe - exploder Gt-40 iron heads, Explorer intake, 19 lber's. E-cam. crane 1.7 rollers. 190fp. 75mm maf. 65mm tb, tubular subframe connectors, mac cai, Asp crank pulley, T-5, king cobra clutch, flowtech 1-5/8 unequals, mac X-pipe Frpp driveshaft, lakewood Lca's. race weight 3,160 12.69 @ 107.35, 1.71 60' 26x8.5 drag's 3.90 gear 13.20 @ 106.91 - 235/60/15 firestones 2.3 60' 3.27 gear

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