Much like many others on this sight I am having engine knock problems. I rebuilt the head this summer and now the compression is rather high and probably uneven between the cylenders as the head was warped very severly and I had the thing milled far beyond volvo's recommended safe maximum. The car ran fine during warm weather but now that it is about 8 degrees here in Pittsburgh, cold starting is an issue. the engine seems to knock for the first 20 sec or so when it is started in the cold. I retarded the timing down to 8 degrees btdc, but it has had only a tiny effect. I am afraid that if I retard it any more that I will have a terrible loss of power as the already underpowered and aging engine is not exactly zippy around town. The engine only knocks upon start-up below about 20 degrees F. There has been no decline in fuel economy and no incidence of knock under load (once warmed up) even when cold outside. I never run any thing other than premium fuel and keep the car well maintained, but this is driving me nuts. Any idea of what an appropriate degree of advancement should be?