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Discussion Starter #1 (Edited)
I have a 3550lb race weight NA 700hp stick car with 11.2 compression running on 93 pump gas. Runs high 9's to 10.0x in the summer heat. 434 SBF with 7721 heads, Super Vic, 1050 carb. Its a Street/Strip (mostly strip) car. The standard variety Autolite 3922 plugs look good with heat on the center of strap but there is an ever so slight hint of detonation on the porcelain on a plug or two using 28* of timing. Motor has a good cooling system and it is cooled between rounds.

I've been thinking of dropping the heat range using a AR3911 plug and was wondering if it was worth using a cooler plug in and attempt to use more ignition timing? Any benefit or just a dumb idea? :rolleyes:
 

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How about some better fuel? Regular pump gas might be on the edge in the motor.
 

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Dennis, I agree on better fuel.

Just to give you another data point. Our combos are similar, with similar times. I run AR3923 for both street and strip, however, I also run 104 Oxygenated fuel and my timing is locked at 28*. I am always inspecting my plugs and they look good. If I run 93/94 pump gas I MUST go with AR3932 otherwise slight signs of detonation on some of the plugs.
 

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In general,...racers tend to run to cold of a plug. The problem with that is, it can cover up issues and giving misinformation.
 

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I just dyno'd a 565 BBC with 11.2:1 compression and an ngk BKR6E plug on straight 93 shell ultra...
No sign of detonation with 35 degrees of timing and I pulled it down below peak torque to see....
Most run too cold a plug on everything....
I like hot plugs, they stay clean....

He'll I run -8 heat range ngks on shit with over 15.0:1 compression and 8500 rpm.... LOL
 

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I just dyno'd a 565 BBC with 11.2:1 compression and an ngk BKR6E plug on straight 93 shell ultra...
No sign of detonation with 35 degrees of timing and I pulled it down below peak torque to see....
Most run too cold a plug on everything....
I like hot plugs, they stay clean....

He'll I run -8 heat range ngks on shit with over 15.0:1 compression and 8500 rpm.... LOL
Yep,.....I encounter this all the time. The myth that colder plugs mean more power. Drives me crazy.
 

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I used to catch heck when I'd show up to the dyno with my normal hot extended tip A/C street plugs in my 871 HP 555" pump gas motor. They never fouled even with the Dominator putting around on the street and I'd leave them in there forever. Never made any difference when we'd try NGK -8's. I tend to like hotter plugs also.

JIM
 

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He'll I run -8 heat range ngks on shit with over 15.0:1 compression and 8500 rpm.... LOL

I ran -9's on my stuff (16.5:1), then ran -8's when I ran out of the 9's because I had them in the trailer. They actually looked a lot better than the 9's after one pass, and showed tuning changes a little better on motor alone....
 

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Yep, you want the hottest, not the coldest, plug that the engine will tolerate without causing pre-ignition.
 

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Discussion Starter #12
I get it (Thanks!) BUT was wondering if increasing the timing a couple of degrees would offset the effects of the cooler plug in a positive way? (Such as increased HP with the minor increase in timing?) Dumb idea?
 

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I used Autolite plugs in a 630 hp bbc and had specs on porcelain and thought I was lean until I looked at plugs coming out of box and they had same specs!
 

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I get it (Thanks!) BUT was wondering if increasing the timing a couple of degrees would offset the effects of the cooler plug in a positive way? (Such as increased HP with the minor increase in timing?) Dumb idea?
The answer is .....N O
 

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100LL Av Gas is better than any pump gas and not expensive for competition use. Just not legal on the street because of no road use taxes paid. Not for use with cat converters though.
 
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