spark plugs

I know that if ya run either hotter or colder spark plugs it gives ya a little more punch(good use of a retro word!!lol).
Now my question is :which one hotter or colder? And i'm running a 400 sbc, with i think"RS44"s( not sure, too lazy to go look) So what would be hotter? RS43 or RS 45?.
and would the 43 be colder or hotter?
thanks
JimV

 

Hotter plugs are good if you are having your plugs foul. Colder plugs are good if your plugs are melting the electrodes slightly or you may be getting some preignition. If none of these things are happening, I wouldn't expect a preformance gain from a plug change.

 

RS45 hotter

 

i agree,,,,i "think" the 43 is cooler

 

Ditto. If your plugs look good, a change either way would very likely be a mistake.

 

My buddy was running a Tbucket with a blown 350 in it & he went to a hotter or colder( he can't rememebr ) plug & it made a big differance!! i drve in it & i couldn't believe it either.
JimV

 

Jim,
Changing your spark plug heat range is only nessesary when your engine combination has been modified to need it. If you change to 1 step hotter than the factory rating, you will have the potential of helping create detination in the cylinders = Bad.
If you change to 1 step colder, you run the risk of the plug possibly fowling, since it will cool quicker, which is not good.
The point of plug heat ranges are based on compression, fuel types, boost pressure, and cylinder turbulence.
And to address plug gap, wider is not always better. Keep it at .035 unless your running a totally different than stock configuration.
If you have any other questions, feel free to ask.

 

Ok cool, thank you
JimV

 

If your buddy did better by changing plugs he prouably was to rich and went hotter to keep it from fouling in stead of going leaner to not be rich. Or maybe whoever built the engine went two steps colder for a blow motor in case he was going to race it and it would see lots of WOT. So your bud went hotter to work better with what he is actually doing. If its firing on all eight now your bud did the right thing.

 

The ONLY way that could have happened was if his heat range was so far off the plugs were fouling and therefore the motor was not firing solidly on all 8. There is no magic horsepower gain with spark plugs, Dyno guys will tell you that a heat range change to get it right is worth very minor power differences unless it wasn't in the ball park to start with. It's done to make sure the heat range is hot enough to fire the mixture without burning up the tip of the plug. Cold plugs won't properly fire the mixture Hot ones won't last.
Pretty sure if you have RS44 in your 400SBC now changing to 45's or 43's will not be a perceptible difference.