Going from race gas to alky...is it IMPERATIVE to change plugs, i.e., colder? 10.8 to 1, sbf, 480 HP. Up to now, 3924 Autolites are working just fine. Nice tan color and never a problem. Why should I change?

I would use 1 heat range hotter than required for gas/compression and .030 gap

What Bart said. ^^^^^

Why would you go hotter than your gas set up???

I would go one step colder with methanol.

Why hotter?

Why colder?

Like to know your reasoning. I run same with gas or alcohol but have not done any testing with it.

I would "think" hotter. People are always complaining about being able to build heat in an alcohol engine, starting it on gas. If you're not putting as much heat in the cooling system you must not be building as much heat in the combustion chamber. But that just logic, those that run alcohol will know better.

I believe you run hotter to keep plugs from fouling. Plugs foul easier on alky than gas from what I hear.

spark plug heat range has little to do with actual engine temperature; lots to do with how well the spark plug dissipates heat. Read your plugs and they will tell you if you need hotter or colder. Mine didn't want anything different than it did with gas, similar experiences with many other cars but everyone's stuff is different.

Guys here is a really good read.

https://www.enginebuildermag.c...ark-plug-heat-range/

I have been running alky since the early 90's and have had probabally 10 different combos. 388 small block to 572 big block. Carburated and injected and chased the plug heat range thing. I found little if none in performance gains. Nothing big at all. Now all the combos were from 13.5 to 14.8 compression, 110 to 114 lobe separation cams and 6300 plus converters. NGK, Autolite,Accell,AC delco and Champion. Now I did find that some combs liked projected tip better and go figure one more step as I hed to index the plugs on those motors. Also timming between 28 and 34 degrees. But I hope more people respond as this was just my own experience and no dyno time just on the track. There has to be some on here that have hours of dyno experience in this area that can shed light in this area.

IM WITH SLICKSTER ON THIS ONE SAME KIND OF EXSPERIENCE WITH DIFF COMBOS AND PLUGS

What I've been told is to run the coldest plug I can that will still fire the mixture.....

Just for everyones information alcohol does not foul plugs. It carries electricity. Gas does not.

quote:

Originally posted by irf3:
Just for everyones information alcohol does not foul plugs. It carries electricity. Gas does not.

I am sure to most of us if the plug isn’t firing then it is considered fouled. A soaking wet plug is considered fouled in my book.
A hotter plug will stay dry better and keep firing properly. Too hot of plug can cause destination by firing the mixture before the plug fires.

Methanol A/F is richer and a tighter plug gap works better in my experience. .022-.024 works for us with the GRID and 8261 coil.

Our A/f on the RP is approximately 5.0 using a NGK -7 plug 13.5cr with Enderle fuel injection.

The OPs CR is on the low side so i would error a little hotter.

Now throw in the discussion on water temp with this too.

quote:

Originally posted by mavman:
spark plug heat range has little to do with actual engine temperature; lots to do with how well the spark plug dissipates heat. Read your plugs and they will tell you if you need hotter or colder. Mine didn't want anything different than it did with gas, similar experiences with many other cars but everyone's stuff is different.

.......Exactly.....

quote:

Originally posted by Coloradoracer:
What I've been told is to run the coldest plug I can that will still fire the mixture.....

.......Wrong direction...

quote:

Originally posted by 62Galaxie:
Going from race gas to alky...is it IMPERATIVE to change plugs, i.e., colder? 10.8 to 1, sbf, 480 HP. Up to now, 3924 Autolites are working just fine. Nice tan color and never a problem. Why should I change?

Depends on the octane of the gasoline. Colder plug makes for a larger window to advance the timing. Methanol, power is heat in the chamber. The engine you're working with is low compression, so what fuel did you use to produce the current plug reading you're basing your question on?

quote:

Originally posted by Mike Rietow:

quote:

Originally posted by 62Galaxie:
Going from race gas to alky...is it IMPERATIVE to change plugs, i.e., colder? 10.8 to 1, sbf, 480 HP. Up to now, 3924 Autolites are working just fine. Nice tan color and never a problem. Why should I change?

Colder plug makes for a larger window to advance the timing

.....I would have a different opinion on that.