Spark Plug Heat Range

[flyin ryan]

well, again, understand there is no definitive good, better or best, lots of ways to skin a cat as it were. everybody that comes to me all want that perfect combination & i tell them the same thing, it depends. lots of factors involved, LOTS. that's why those desk top dyno things don't work. i just want to make it clear i'm not saying what you're doing is wrong & what i'm saying is right, i want to help best i can but i have minimal information about your deal to be fair. based on my testing & what my friends in the engine building world are using these days i'd stick closer to .035"-.040". now for the E-3's? i'm a loyal NGK guy, never heard of these? don't know anything about them. i'm chasing power in a lot of areas but spark plugs are not one of them lately.

[XfireZ51]

FR,

Not a problem. Fully appreciate your help or anyone else's on this forum.
As part of tuning the motor, I wanted to make cetain I had the proper heat range plug in the motor. With the right heat range, you can tune the motor with greater accuracy. Having read quite a bit on the subject, heat range for a plug is determined by looking at the ground strap and seeing where the color change appears on it. Too close to the tip of the ground strap, plug is too cold, too close to the base ring of the plug, then its too hot. My color change on the AC 41-602 were right at the base ring. I'm going thru explaining this for the benefit of some of the others, not necessarily you.
The 7 heat range plug, based on how to read the ground strap, seems to be closer to the arc of the ground strap and so closer to correct.
Having said that, I now find that I have a problem with a Code 55 or Lean exhaust. Something is causing the injectors to drop out and therefore a lean condition. I have a scan on it. Lgaff and myself checked the fuel pumps and they both turn on to 48psi then drop off to 42 with Key on, motor off.
I am currently suspecting a flaky TPS or something having to do with timing. Its not the Port Throttle. No code and it has the right signal to stay on. Something else caused the injectors to close down at around 7100rpm. When it went lean, that set the code and so the ECM disabled secondary. My only other suspicion is the Fuel Kill which was set at 7175.
I'm also going to close the gap on the plugs on the off chance the wider gap is taxing the coils.

[flyin ryan]

can't hurt to try might help. interesting problem

[jonszr1]

maybe i am nuts but i just love trying things when tuning to try to get as much as possible out of the combo. cant do a throw a cam in it like a standard small blk chev. so trying things tune wise keeps an ole guy happy

[ZWILD1]

I use AC rapid fire #8's gapped to .045 th. I changed over to NGK BKR5EIX's . I wanted to go back to the rapid fires and I get tappered seats no washers. I swore the #8's I had before had washers. I accidently threw the old ones out. Am I crazy or just mistaken.

[Aurora40]

You need #5's not #8's for a '90-92. Why would you want to go back to them from iridium plugs, though?

[ZWILD1]

Eights are one range colder and seemed to work good for me. I posted a new problem though have you had problems with rough idle and lose of power with your car.