hi everyone.

can anyone give me any info on spark plug heat ranges and proper gaps?

somewhere in the last 30 years, the heads were replaced on my car.  i don't know much about them except they are "double hump", 2.02 heads. (not really sure what that even means ) anyway, the plugs i am currently running are AC DELCO R45S.  (these were in the car when i got it and decided to use the same when i changed plugs). The car seems to run fine but how do i know if they are the correct heat range or if i have them gapped properly?  i have them gapped to .035

who knows.  if i went to a different plug, the car might run better than i can imagine.  i just don't know how to determine what plug may be best.

thanks.

jeff

 

Well, from what I see in the ol' tune up specs a '74 vette (all engines) used a R44T plug with a .035" gap. I'm assuming that you are still running the original breaker/points distributor. Or did you convert it over to HEI?

'75-76 vettes used a R44TX W/ .060 gap plug. Then '77-'82 used a R45TS W/ .045 gap plug.

How do the tips of the plugs look? Light tan, sooty black, ash deposits, blistered, yellowish, melted?

Brownish/ light tan is good.

Sarge

Sarge,

the car had been switched over to an HEI distributor.

my plugs vary. 

#1 plug is almost always somewhat wet with oil deposits (blowby in that cylinder maybe?)  i have a couple plugs that are sooty black but the rest are brownish tan and seem to be running well.

you mentioned that 75-76 vettes had a gap of .060.  that seems pretty drastic,  that's where i'm confused.  why would one plug be gapped to .035 an another be .060??

maybe this is just too much for my feeble mind...

The HEI('75-up) systems will use a much larger gap. .060 would be about right on the early HEIs. You could probably get away with running R43's if you wanted to do a little high speed runnin. The R44s would be better. Just be sure, whatever heat range you run, get the "Extended tip"(signified by the "X" in the part #) plugs, so you'll be able to run the wider gaps.
Your "feeble mind" is OK...just needs a tune-up!!!

thanks for the info guys!

i'll try to pick up a set of the r44s with an "x".

do you suggest i go with .060 gap with them?  what happens it i have the gap too large or to small? 

if i didn't have you guys to ask, i'd probably never know what plug or gap to go with.  is there some "secret society" that is hiding this info from me and the rest of the world?

I'd start with a .045 gap. The original HEI systems used a larger gap, but then it went to a .045 once they realized it would work just as well. Do that, and make sure your wires/cap/rotor are all in good condition.

The .060 plugs did have problems.  They created enough resistance that the car had a tendence you burn the dist cap, and actually burn through the rotor, causing the rotor to short out and the car lose spark.  There were several TSBs recommending that the .060 plugs be replaced with the .045 plugs to correct these problems.  It was also found with the smaller gap, there was a longer spark duration, making the engine operate just a bit better under some conditions.

i don't have headers.

you know, that's a good question.  i don't know what the "s" is for. but i went to autozone to look at the extended tip plugs and they look at least 3/8" longer in the threads than the R45S that i'm using.  heck, they look like the piston will bang into them

[QUOTE=Hmel '74]

Sarge,

the car had been switched over to an HEI distributor.

my plugs vary. 

#1 plug is almost always somewhat wet with oil deposits , why would one plug be gapped to .035 an another be .060

[/QUOTE]

Maybe that was a quick road side fix when a plug fouled out.