Joe, you should start with 2 heat ranges COLDER and if it works, stay there. If they foul after a few hundred miles of putting around, back up one heat range.

Messing with heat ranges might seem like a lot of trouble sinnce our plugs can be a bear to change, but you will learn to do it better during that time

 

Kevin, Thanks for the info. I'm looking to use NGK Heat range of 7. Regarding my earlier post above which wasn't really phrased right, I was wondering how much affect N20 had on plug selection. If I add N20 on a boosted engine, how much colder should I go? If I remove the N20, how much warmer should I go? Assuming I decide to use a 75 shot. One or two heat ranges? It seems to me that the use of N20 requires a colder plug than the same HP level of boost. ps. thanks to the original poster for bringing this subject up.

 

There are some other threads about plugs worth searching & reading. With Nitrous you still need about 1 heat range colder per extra 75-100 hp over stock just like for boost, but you also should switch to a non-projected tip design. You should run the coldest plug that will not foul out. These are just rules of thumb which are published by the plug manufacturers.

 

NGK from hot too cold


hottest
TR5
TR6
BP7EFS
R5724-8
R5724-9
R5724-10
coldest

THE -9 works well on high compression 12.9:1 and a 250 shot with total timing in the 23 degree area

 

Have any of you ever used one of these spark plug heat range tools that was featured in a tech article in the Aug. issue of High Perf Pontiac ( www.determinator.net ) ?

 

That thing looks like a $129 piece of crap to me.

 

yea, I couldn't figure out why I think it was bohanz did an artical about it and was so excited... as far as I can tell it's just a mechanical depth guage that reads out on a scale (hot to cold) vs an actual depth, measuring the center ectrode... I don't know how that could accurately tell you heat range.

 

But, for your $129, you also get a spare cover for it... That alone almost makes it worth the purchase price :blah:

I'll tell you, I'd be one pissed **** if I bought one of those things thinking I was getting some kind of hi-tech plug analyzing instrument and found out it was just a stupid depth gauge with a book telling you how to read plugs, which is basically the same info that is in every ignition and car manual and is available in any spark plug catalog or web site for free. They got a lot of ***** selling those for that much money cause they're going to have some really pissed off customers that didn't bother to watch the whole agonizing video to see how the POS actually works.

It's almost comical to look at the examples they give of the plug with the ground electrode melted off and one with the porcelain insulator cracked off "This plug is too hot. You need to select a colder plug" Well no SHT. They make the guy selling the TB Bypass Kits on Ebay look like a saint.

 

Reprint from HSW posted at LS1 Tech

Thread – 14mm
Reach - .708”
Socket – 5/8 hex
Seat - Taper
Stock Heat Range: 5
Gap: .060
Plug: NGK TR55 (stock number 3951); NGK TR55IX (stock number 7164); Autolite 764; Denso IT-16 (stock number 5325)

Nitrous (one step colder)
Heat Range: 6
Gap: .035 - .038
Plug: NGK TR6 (stock number 4177); NGK TR6IX (stock number 3689); Autolite 103; Denso IT-20 (stock number 5326)

Nitrous (two steps colder)
Heat Range: 7
Gap: Consult
Plug: NGK BR7EF (stock number 3346); NGK TR7IX (stock number 3690); Autolite AR94; Denso IT22 (stock number 5327)

Nitrous (two and a half steps colder)
Heat Range: 8
Gap: Consult
Plug: NGK R5724-8 (stock number 7317); NGK TR8IX (part number 3691); Denso IT-24 (stock number 5328)

Nitrous (three steps colder)
Heat Range: 9
Gap: Consult
Plug: NGK R5724-9 (stock number 7891); Autolite AR93; Denso IT-27

Nitrous (four steps colder)
Heat Range: 10
Gap: Consult
Plug: NGK R5724-10 (stock number 7993); Autolite AR92



I am running AR 94s N/A and AR93s for juice(200 shot). My Ignition is VERY hot with Four MSD coils and a DIS-4 Plus box running wasted spark. Just in case I always have plugs heat range 5 to 11 on hand Some one ALWAYS needs a set!

 

Hey Ellis, I'd be interested to know if you see any longer term wear on your plugs from switching polarity on them for wasted spark. If you see anything wierd like ground electrode wear, let us know, OK?

On the other hand, maybe you change plugs frequently enough that you don't have wear on them...

 

You bet Kevin. we are still getting all the bugg's out. I have heard the plugs will stay cleaner with wasted spark but run much hotter needing the hotter plugs.

Once we finally get the bug's out we may need to go up one more heat range on both N/A and N2O

I can tell you this. Hard as hell to tell when one of the coils is un-plugged at an idle some times