Originally Posted by
Walter Atkinson
If one insists that EGT is a factor, please reconcile the preignition DATA that Jabba posted. We have a bucket full of these files and in every case, it is the same. Falling EGT, rapidly rising CHT. How can one with intellectual honesty suggest that during pre-ignition that the valve is running cooler because the EGT is falling?
It IS a factor, just NOT THE ONLY ONE... In the pre-ignition case considerably more heat energy is transferred to both valve and cylinder head and less is available in the exhaust gas, that is demonstrable. The heat is both generated and transferred to the cylinder head and valve earlier in the engine cycle.
The post from Jabawocky does not present any data with valve temps...