Cylinder head temp gauge

Mainly running thermocouples to a bolt on the head. Most billet hemi heads have a threaded bolt hole in the middle of the head near the deck below the headers. Very important data to monitor in my opinion. EGT's definitely don't tell the whole 'tale.'

 

Methanol loves pressure and hates heat. Years ago racers ran a real hot head temp because the ignition systems needed some help. For comparison a MSD 12 amp mag has about the same output as a 6-AL MSD box.

Depending on your application, will dictate what you can get away with. It is going to be directly correlated to your idle flow. If you are dial in or index racing and not pushing the envelope, you can run a leaner idle and a little warmer head temp. If you are running heads up, I like to run it cooler. A hot head temp will give you a very responsive/aggressive horsepower off the line, but you can't push the tune up as hard down track without risking getting into detonation due to the warm cylinder head temp. Running a cool head will puke the oil up quite a bit more. When I'm running heads up, my goal is win lights, not to see how many runs I can get on the oil. I see a lot of folks base their idle mixture, and therefore the tune up, around what does or doesn't puke the oil so they can get 2, 3, 4+ runs out of the oil.

Where the bung is located is going to be relative to what kind of head temp range. You don't want to get too close to an exhaust port. On my hemi stuff with the central location, I don't want to exceed 165 in any application. Heads up 'well' below that. I reference the number right before stage. It rarely changes down track and does not respond quick enough to be a real tuning tool down track. It's all about where it is going into stage.

That said, when you are lean enough that you are going into stage 170+, your stage head temp is going to be increasingly sensitive to run time. So if your opponent takes their time, instead of 170, you might have 185, 190. 5 degrees change is noticeable. 10 degrees may be the difference in a tune up making it and not.