What plugs are my fellow racers using in their (drag) race engines in the 11+ SCR range?

225 cuin
11.37 computed SCR (using actual measured specs)
Cam intake .540 lift and 286* duration
Cam exhaust .516 and 278* duration
lobe separation 105*
oversized valves in mildly ported head.
4 bbl carb and headers
HEI ignition

I put a set of NGK ZFR5N (3459)
I have yet to fire up the engine to see if any changes/adjustments need to be made.

Just curious as to what others are using.

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-MattMan
LEANED & MEAN

I advise you to NOT use an extended tip plug in a high compression or boosted motor. IIRC, the plugs you list are extended tip. These are really for emissions and MPG and I think the gains even there are minor (with modern ignition systems). These plugs can heat up locally and cause detonation. A few hi perf/racer Slanters have damaged motors using these and had no trouble after switching to a standard tip plug. In my peanut plug heads, at 11:1 with a cam about that big I have been using NGKs in the 5-7 heat range. UR5, maybe? I am not at home until tomorrow night, so will have to look when I get back. There are threads on this site, so try a search. In a Champion plug you want a 9 heat range or so. In Autolite, you want a 3 heat range.

That is exciting that you are about to fire up your new and long-planned engine. Congrats!

Lou

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Home of Slant6-powered fun machines

I can look and tell you what is in my 11.5 to race motor. It is the old drool tube head. I also have a chart somewhere that the engine builder gave me. They only use NGK in their race motors.

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2 Mopars come with Spark plug tubes. One is a world class, racing machine. The other is a 426 CI. boat anchor!

12.70 @ 104.6

B6ES or B7ES. 7 is a bit colder.

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Part of Tyrde-Browne Racing

Yes, I am really excited to hear this thing run. I was a little leery of the NGK plugs I put in it. They seem to be more extended than I am used to.

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-MattMan
LEANED & MEAN

I think CJ has posted what I have in my car. To clarify, you have a drool head or peanut head?

Lou

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Home of Slant6-powered fun machines

NGK B7ES, sound great. I can now run the same plugs in my Dart, D150, Aermacchi Harley-Davidson Sprint and Yamaha XS2!

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“Buy the ticket, take the ride.”
― Hunter S. Thompson

Yes, it is a drool plug head. From a 73 slant.

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-MattMan
LEANED & MEAN

Just my personal preference, but I wouldn't put an NGK plug in a freaking weed whacker. I just have never had any luck with them.

IIRC, I have Autolite 25's in my junk.

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Official Cookie and Mater Tormentor.

Myself, I have had just the oposit (sp) result. I used to use autolite plugs, but years ago they started making them in China. I had bad results with them (blowing the porcilin out of the shell). Some are made in Mexico, and they seem ok. So my advice, is to check the box, and see where they are made.

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Charrlie_S
65 Valiant 100 2dr post 170 turbo
66 Valiant Signet 225 nitrous
64 Valiant Signet
64 Valiant 4dr 170

So, disregarding Brand names, high compression NA engines do not particularly 'like' extended tip plugs. So, the style is basically a stock style plug in the heat range the engine likes?
I'll just start with the stock style and go from there, unless anyone can recommend what works for them in a similarly configured engine.

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-MattMan
LEANED & MEAN

To confuse things some more.

There's at least 2 types of extended tips.

Normal plug (NGK B7ES) (and BR7ES for resistor plug)




Slighty extended (NGK BP7ES) (BPR7ES)




Super extended (Autolite 985) (resistor)




I can see the super extended having problems in a high performance engine, but the slighty extended I would think would be fine.

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Ed
64 Valiant 225 / 904 / 42:1 manual steering / 9" drum brakes

If you look at the ground electrode on the b7es and the bp7es, the b7es is shorter. Being shorter, it will conduct the heat away from the end of the electrode faster, and run cooler (the electrode not the plug heat range). In a boosted or nitrous application this can be critical. Even if the plug heat range is cool enough, the ground electrode can get hot enough to "glow", and that can cause preignition. It will act just like a glow plug. I have even gone as far as cutting the ground strap shorter, bending it down, and "firing" from the side of the center electrode, to the ground strap.

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Charrlie_S
65 Valiant 100 2dr post 170 turbo
66 Valiant Signet 225 nitrous
64 Valiant Signet
64 Valiant 4dr 170

Well, the NGK ZFR5N looks like a 'super' extended tip. That is why I was asking. I typically have had good results with extended tip plugs on big blocks. I am still learning what a hot slant will like.

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-MattMan
LEANED & MEAN

The super extended plug is not good for a race motor from what I'm told.

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2 Mopars come with Spark plug tubes. One is a world class, racing machine. The other is a 426 CI. boat anchor!

12.70 @ 104.6