I plan on having ~450rwhp with my solidroller/LT4 headed 396 setup. I did a search and choosing the proper heat range for plugs on an LT1 doesnt seem to be all that popular of an idea. Ive always been told to decrease a heat range after an increase of 50hp NA. So at that rate Id need a plug thats 5 heat ranges lower for my NA 396?

What do you guys think/what have you found? I cant see the sense of running a stock plug in a motor like this.

 

I'm saying leave er' alone.. Go colder if your sprayin'.. thats what i've heard anyway.. I'm no expert.. you'll be fine w/ a stock plug..

 

I run an AutoLite 103 on the street.... 2 steps colder than stock. That's with about 500flywheelHP.

 

Is that for spraying as well? or just N/A?

 

Thanks for your input Fred. Why does spark selection seem to be such a minor detail with LT1 guys?

 

Ive been wondering about plugs too for my new 383 (500-525 fwhp). I have a new set of stock replacement AC platnum plugs, but wasnt sure if they would be the right ones to use or not.

 

Any increase in cylinder pressures whether they come from nitrous, forced induction or hp increase due to modifications will probably require the use of a colder plug. That's no big secret.

The question is, "How cold a plug?" and you're going to have to try a bit of experimenting to determine that. I'd experiment around with a set of plugs 2 heat ranges colder than stock to start. Don't buy expensive platinum or iridium plugs cause you may be chunking them in the garbage. Since we're talking street car here, that's where you want to test. Then pull a plug or two and check them out. There are guides online for plug reading if you don't know how. That will let you know which direction you need to go.
If you're pushing the limits on compression... weather is hot out, whatever, changing to a colder plug is a good change as long as the plug can run hot enough to stay "clean".

I run a Champion C59YC in my car, but the cylinder head is a "race" head used in class racing. That's the "starting" plug recommendation for these heads and going to a colder C57YC cause some fouling. But these are heads generally used in engines making 750+ hp so the C59YC is more than adequate with my ~550rwhp motor.

Good luck.

-Mindgame

 

Thanks for the repsonse mindgame.

 

NA only. When I spray the full 300-shot, I run Champion S57YC, but they are so cold they will carbon up in the staging lanes if I sit there too long with the engine running.