What is the rule of thumb ? Compression goes up does heat range go cooler ? How many of us use the oem heat range, after bumping up the compression.
CK5
Register an account today to become a member! Once signed in, you'll be able to participate on this site by adding your own topics and posts, as well as connect with other members.
plug heat range and compression ?
- Thread starter Wes Harden
- Start date
Iirc, as performance goes up (significantly) the heat range comes down a little.
I'm not running anything real spicy but at 9.5 comp I still run an Autolite 26 / Delco R45TS plug.
I'm not running anything real spicy but at 9.5 comp I still run an Autolite 26 / Delco R45TS plug.
A general rule we went by at the speed shop was one step colder on the plug for every full dynamic point in compression.
Fuel type would play into this as well as if it was turbocharged or blown and N.O.S. brought a whole bunch of rules and theory’s to the game.
Keep that chamber temp as hot as possible w/o creating an overheating condition - so don’t go too cold.
On a street/trail motor the cam profile can alter the heat range choice v/s a motor that is usually gett’n plenty of airflow like fly’n down the track and being allowed to cool off.
Fuel type would play into this as well as if it was turbocharged or blown and N.O.S. brought a whole bunch of rules and theory’s to the game.
Keep that chamber temp as hot as possible w/o creating an overheating condition - so don’t go too cold.
On a street/trail motor the cam profile can alter the heat range choice v/s a motor that is usually gett’n plenty of airflow like fly’n down the track and being allowed to cool off.
Attached is a chart of spark plug recommendations for Dart heads. The interesting thing is you can see how their recommendations change for compression ratio.
Is that chart from Dart? If so, it appears their go to brand is NGK and not any typical American plug.
Seems like I remember a David Freiburger video where he said that from his Engine Masters experience they preferred NGK or Denso plugs. I was surprised because for years folks were hot for Autolite but I guess they lost quality somewhere. The same video also discussed how to tell the difference between US vs foreign made AC Delco plugs. I need to find that video for a refresher.
Seems like I remember a David Freiburger video where he said that from his Engine Masters experience they preferred NGK or Denso plugs. I was surprised because for years folks were hot for Autolite but I guess they lost quality somewhere. The same video also discussed how to tell the difference between US vs foreign made AC Delco plugs. I need to find that video for a refresher.
Yes. Here's the link: https://www.dartheads.com/wp-content/uploads/2024/02/Dart-Spark-Plug-Application-Sheet.pdf I just found that recently because I needed to change the plugs in the C10.
I've been using NGK at @folkenheath's recommendation. Otherwise I've never been married to a particular brand.
NGK and ND make a fine plug!
Not sure I am sold on the NGK UR split tip.
Don't remember which plugs I have in the burb atm either R45ts or R43ts, it's due for some. Since my swag compression math has mine between 9.5 and 10, I was thinking of going cooler
Don't remember which plugs I have in the burb atm either R45ts or R43ts, it's due for some. Since my swag compression math has mine between 9.5 and 10, I was thinking of going cooler
This is an interesting topic that I never thought of.
I just bought new plugs for my burb and recently went from about 9.5 to 10.7.
I'm not even sure if the heat range I got is even close to the ones I had...
Just looked up and ls3 vehicle on rockauto and picked a set of delcos.
I just bought new plugs for my burb and recently went from about 9.5 to 10.7.
I'm not even sure if the heat range I got is even close to the ones I had...
Just looked up and ls3 vehicle on rockauto and picked a set of delcos.
Higher compression creates higher Temps. The need for a hotter plug wouldn't be as critical as say a low compression smog engine, in my view
I’m not certain but heat range choice might be different from old school heads compared to an LS with an entirely different cooling flow system that allows such high compression on pump gas.
The chamber gets cooled by much cooler water on LS type engines.
I’d do some specific LS plug heat range investigating instead of comparing what old dinosaur engine methods are.
I noticed with the new setup, I can start my engine, pull out of my spot at work and within a half mile I'm over 130*. That surprised me.
you have tight tolerances helping build heat, it will lessen as it breaks in.
I am thinking about trying NGK UR6IX in my gen 1, iridium. NGK the high number is cooler
Yes in general hotter compression needs a cooler plug to avoid detonation from too hot of plug tip, up up a point of compression usually means dropping one plug temp at least in NGK terms.
I prefer NGK because there plating/coating on the plug is less likely to seize in an aluminum head. I've had other plugs try to seize on me even with antisieze on the plug, I have not had that feeling with NGK thus far, and I have been using them for years.
Plus I called NGK 7 years ago about my 11:1 big block that I add nitrous, and they told me exactly what heat range to run and what plug gap with each nitrous level and NA, tech didn't even think about it, just spouted it out right away like he does it 10 times a day.
I prefer NGK because there plating/coating on the plug is less likely to seize in an aluminum head. I've had other plugs try to seize on me even with antisieze on the plug, I have not had that feeling with NGK thus far, and I have been using them for years.
Plus I called NGK 7 years ago about my 11:1 big block that I add nitrous, and they told me exactly what heat range to run and what plug gap with each nitrous level and NA, tech didn't even think about it, just spouted it out right away like he does it 10 times a day.
So Ngk UR4-5 is stock smog or normal compression, the a 6 would be a reasonable choice
He probably does
