Contour Enthusiasts Group Archives Forums Modifications Zetec Performance milled head=knock when cold

i have a 97 contour zetec engine. i milled the head not long ago because it got warped. runs great when the engine is warm or its warm outside but when its a cold engine and cold outside it runs like crap. it will make a knocking sound until it warms up...the colder it is outside the louder the sound. also the lower the octane gas i use the louder the sound. i know milling the head causes the compression ratio to go up...is there a mod to do to compensate for this?

does it sound like i need to retard or advance the timing?

is there a way to fool the engine into thinking the air temperture is different from what it really is?

any suggestions


Thanks

What does it do when you run premium fuel. I suspect that by milling the head you've upped your compression ratio and few tenths and put yourself into the premium range. The only solution to that is to put a thicker head gasket on to lower the CR.

I milled my head, also due to warpage, and I've gotten along okay by just always using premium gas.

How much did you mill the head ?? Milling 0.023-0.024" will bump the CR from 9.6 to 1 to approximately 10.2 to 1.

Oh, mine got milled a lot more than that. The CR is probably close to 11.

I have a 96 Mystique that was making a hell of a racket, it turned out that the timing belt was hitting the inside of the cover. I had to replace the tensioner and the timing belt (150,000km's). Runs great now. Just take off the cover and start it up, you'll see it. Good Luck.