Head temp differences, How big is too big? Options

[lapuwali]

I recently fit a CHT gauge, and originally put the sender under the #4 plug. Readings were in line with what I've read here: idled at 300dF, cruised at 325-350dF, touched 400dF under heavy load (lots of long uphill grades here).

I moved the sender to the #1 plug yesterday, and the temps are as much as 50dF lower across the board. Idles at 250dF, cruise about 300dF, never exceeds 350dF even pulling up a long hill.

I expected a difference, but not 50dF (20%!) between heads. I'm running Webers, so it's possible I have completely different mixtures for each cylinder. I presume cooler head temps would usually mean richer? This would be in line with plug colors (blacker on the 1/2 head, tanner on the 3/4 head). Hmmm....

[Jake Raby]

Bank to bank... meaning:

cylinders 1-2 are a pair..
cylinders 3-4 are a pair.. I'm speaking of differences from bank to bank.

When you install a CHT on all 4 cylinders you'll see that both on the same side run within 5-10 degrees of each other and the rear cylinder is a tad hotter..

Even on a Harley this happens with the rear cylinder, its being cooled by preheated air from the forward cylinder.

I have been working on cooling system stuff for 2 solid years, and intensely for the last year... All I have really learned is until you have 9PSI, the air inside the plenums cannot be directed.. Thats the only general rule so far... everything is dependant upon something else!