[Jim Wahl]

Originally Posted by Adger Smith

Advanced cam opens the ex valve earlier. If it is still hot in the chamber that earlier opening will usually let hotter gases into the ex pipe. Try retarding the timing and watch the ex gas temp go up, but don't try advancing the timing until the EGT cools down. You will end up with melted/broken parts in the cylinder/engine. There are quite a few variables that affect ex temps. I know I'll get some flack for this statement, but there is no "one" ideal ex gas temp for every engine combination. There will be an ideal temp for "each" engine combination that is tuned correctly. The engine will tell you what it is. I get a smug smile when someone tells me they can tune by just ex gas temp. It helps to know them and plot the changes, but EGT isn't what makes a tune up correct.

Especially important in a turbo engine! Jim

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