Spark Plugs?

[earlbrown]

Spark plug heat range has nothing to do with coolant temp, head temp, or cylinder temp.

It's just a description of how thermally coupled/decoupled it is from the 'cold' cylinder head.   A hotter plug has an electrode that's hanging out like a big ass heat absorbing heat sink.  A 'cold' plug has a very short projection.  It's just a description of the physical layout.


The only reason the adjustability is there is to fine tune around the exact engine and usage.  Too cold, and the plug can't get got enough to burn off the carbon. Carbon is conductive, so as soon as a path from the center electrode hits ground, the plug is shorted and can't fire.   Too hot, and the spark plug suddenly starts acting like a glow plug.  Also not good.


The window is pretty wide between those two extremes.   Since we're hotrodders and push our engines to around double the factory HP, the window gets narrower  (and spark plug QC becomes much much more important).


Picking out the heat range is easy. Put in a new set of plugs, kick the shit out of it, pull the plugs and look at the first few threads. You only want a couple of threads looking dull and 'burnt'. If 6 or 7 threads are obviously color changed from heat, you need a colder plug.


 There should be a color change band right in the curve of the side electrode.  That show timing, but this thread doesn't pertain to timing....

[Scoobum]

43's worked fine from idle to 28 PSI. I have a friend that wrenches on a Super Stock car. Think it runs 9's and is NA. On back to back dyno runs changing the gap made no difference in HP.

[nocooler]

http://www.ngksparkplugs.ca/tech-info-spark-plugs.cfm

Plugs remove heat from combustion chambers...... or so says ngk.

[Steve Wood]

A wide gap seems to improve idle and increase plug life on longer cammed, rich idle car and reduces plug fouling.  Multi-spark ignition does the same thing.  Better burn, better emissions.

All these high voltage, plasma, or whatever ignitions seem to do nothing for hp as long as the spark is adequate to light the mixture.

[earlbrown]

Yep. It's a binary thing.   The plug either lights off the mixture correctly, or it doesn't.


If you're already lighting it off correctly, you can't light it off 'even more correctly' and see a HP gain.

[Steve Wood]

Looks like NGK UR-5s are the choice by far

[Just a Six?]

Good reading material, I'm starting to get ready for my spring time oil change & see what's up with the plugs. I think I have some Delco & maybe some NGK from years ago but I don't know for sure. I'm also going to try the Restore Oil Additive for before & after compression numbers. I'll start a new thread when I'm done but work hasn't slowed down during this Virus so it may take a while. 
Cheers & Happy Hot Rodding!   

[Tim Hensley]

I have ran the autolite 25 heat range and life was good. I did try a set of NGK UR-5 ran good but the heat rang just a tad bit cold. Nothing to worry about, found that the Autolite 24 is in between the UR4 and 5  the Ur 4 is the NGK plug for our Buick. I hope the 24 it’s a good fit. My 25 wasn’t really to hot but it wouldn’t hurt if it was a little cooler

[Steve Wood]

From autolite, I like the 23 and the 23 racing.  Seems to work well with all boosts.  I always thought the NGK UR5 was good, but, but the 4 is even warmer. 

[Scoobum]

CR 43 TS from your friendly GM dealer.

[Just a Six?]

After the winter car cover came off I started the car to get oil pressure but only ran it a minute so engine was cold when testing.
I pulled all plugs out & did my compression check & this is what I got. I'm going to check them again so I'm sure of the numbers now that I've been for a drive. After that I'll add the Restore & see what happens. 
   

#1  145                    #2  155                       
#3  145                    #4  145
#5  145                    #6  155

[Steve Wood]

that will be interesting!  those numbers are not bad at all

[daveismissing]

David, you've changed.
I'm sure there was a time when you would have yanked that engine out for a 10lb spread!

[Scoobum]

Good numbers.

[Just a Six?]

Steve you know me too well  it's actually been on my mind since the engine is over 10 years old now & has a few of the typical leaks & it's pretty dirty. My back is feeling half decent so I figure it might be a now or never kind of thing? Probably take me a couple months & my only concern is getting the trans back in with motor installed. Mike login "TType White?? with the White T that runs 9's or 8's? was always my go to guy to come over & muscle it in but we haven't spoken since the last install. Maybe one of the younger guys wants to make some $$ to take the family out for dinner? What to do what to do?