What spark plugs?

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mshred

mshred

The Green Manalishi
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just wondering what some of you guys are using for sparkplugs on your smallblocks.

my car is a mild 340 combo and right now im trying to get the carb tuned properly from reading the plugs, but so far its telling me i need a hotter plug...i figure before i do anything to the carb, get the hotter plugs and then see what the jetting reading looks like on them...im currently running champion p#RN12YC which are stock replacement plugs for the sbm

What plug do you guys recommend? how far up in the heat range should i go? also, i always thought that a performance engine would want a colder plug generally, or is that only in boosted/nitrous apps?

all suggestions appreciated
thanks!
 
i should also mention that i have them gapped at .40 to try and take advantage of the extra spark on my mallory 685 box
 
Try a set of the NGK BKR5E-11. They are pregapped at .045. Perfect for a CD type ignition box.
 
redfastback said:
Try a set of the NGK BKR5E-11. They are pregapped at .045. Perfect for a CD type ignition box.
Click to expand...

will do....are these plugs hotter or colder than what i was using? was the method i was using for checking the plugs correct, or would you do it another way?
 
You check the strap. But you need to install the .045 gapped plugs first, THEN after a WOT blast, check the plugs.

Actually, my bad. The plugs you have transfer over to a GR4. A colder plug would be a GR5.
 
Autolite 3924's gap them at 040...champions are for lawnmowers..
 
stroked 340 said:
Autolite 3924's gap them at 040...champions are for lawnmowers..
Click to expand...

yea i know the champions are stinky...i had em lying around though, so i thought id use them since pockets are so deep these days

as far as heat ranges go though, are the plugs you guys recommending colder or hotter than what i currently have?
 
mshred said:
just wondering what some of you guys are using for sparkplugs on your smallblocks.

my car is a mild 340 combo and right now im trying to get the carb tuned properly from reading the plugs, but so far its telling me i need a hotter plug...i figure before i do anything to the carb, get the hotter plugs and then see what the jetting reading looks like on them...im currently running champion p#RN12YC which are stock replacement plugs for the sbm

What plug do you guys recommend? how far up in the heat range should i go? also, i always thought that a performance engine would want a colder plug generally, or is that only in boosted/nitrous apps?

all suggestions appreciated
thanks!
Click to expand...

..............Actually the stock champion is a RN9YC 4 a 340.............kim.........
 
oldkimmer said:
..............Actually the stock champion is a RN9YC 4 a 340.............kim.........
Click to expand...

well, when i went to the champion site and did the plug search for my car it gave me the plugs i already had at home for a 340
 
NGK R5671A-7. I would use a -8 or -9 for bottle feed cars.
 
hey guys,

turns out i was reading the plugs wrong...here are some pics of them...they look like i need a colder plug after all...however, how many steps should i go down? is the one enough? please take a look and let me know what you think

IMG_1162.jpg


IMG_1163.jpg


IMG_1164.jpg


IMG_1165.jpg
 
I think they look pretty good ,other then the oil from a valve cover leak i think you have.
It's hard to read a plug sometimes when your getting close to a perfect tune,but when you get that close,you start jetting for the kind of weather that your running in ,or as a good rule to follow,just jet the car to run leaner in the heat.
When it starts to get colder in the fall ,bump your jets up for the fall air.
You can hear the differance in a motor thats to rich.
It will not rev-up as fast under throtle and will act lazy and run not as smooth in the upper rpm's.
The engine with to lean of a jet, will do the same kind of thing as far as reving slow ,but will just not pull any rpm but will sound pretty smooth.
You want to keep the motor as fast reving as possible under throtle.
When you start to get to rich it will start slowing down on how fast it rev's up when going threw the gears.
If you go to the track,your mph is a good indicator of horse power.
 
looks like a tad too much total timing by the way the tang looks.

maybe try 32* total, initial don't look bad, not to say you couldn't run a lil more.

yellowing on the tang from heat/or some kind of fuel deposit.

if you look down into the plug, what color is it where the ceramic meets the steel body?
you may be a lil rich in the primary.
you could go 2 steps lower in the primary and see if it surges at 50 mph cruise, if not go another jet down till it just starts to surge, then go back up 2 jets.
 
Hey Guys thanks for the responses!

yes i did have a valve cover leak! lol
as far as timing goes, right now its 16 initial, 36 total, but i want to turn up the initial and lower the total and see what happens...however for now im going to keep it this way. Tommorow i am going to the track with it to see how it runs, will be trying different launch points and bringing a jet kit with me to see what the car likes as far as jetting goes...i thougt as well that the plugs looked a tad rich, so ill try jetting down and see what happens

I dont have a spark plug reader so its a bit hard to see in where the ceramic meets the steel.

As far as heat range goes though, does this plugs heat range look okay or should i go colder? one step? two steps? id like to go buy a set of plugs tonight so i can bring em to the track and do a fresh plug reading after a pass

thanks for all the help so far guys
 
I would go at least 1 step colder, if you look close, at least from what i see, those plugs are "glazeing", thats normally from rappid excell. & too hot a plug, remember this, a plugs heat range is based on how fast it transfer heat "away" from it, not the opposite, another strong indication is the amount of the plugs strap is clean, notice how far down "too the threads" is clean, it should be right in the middle. Plugs too hot!! My 2 cents
 
heat range, too cold-it can't clean itself and fouls,
too hot- can cause pre ignition from the plugs 'excessive heat' preigniting the fuel before spark even happens.
it's a cleaning thing.jmo

and heat range does not change the mixture, it just fools some tuners into thinking it does by either being too cold and showing rich/fouling or too hot and cleaning itself of any mix trace giving the impression of lean. jmo

the timing is shown on the strap, it being clean makes no diff to me, it's the white shadow marks left from the total & initial timing, the total being way down the tang almost to the base ring shows a lot of total while the upper portion shows initial which is a lil low but not bad.jmo
 
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