i bought for one of my daughters a 940 wagon which the po had had a new head gasket installed because it overheated. the car was/is a 93 regina wagon.

the car was in really fine condition when i went to look at it for inspection to perhaps buy it.

it ran beautifully and passed every one of my prebuy inspection points.

long story short my daughter asked me a 2 months after owning to come and listen for strange sound in the timing belt area. sure enough it was subtle but not what i epected to hear.

i removed the upper cover and lo and behold there it was. the po had not only replaced the head gasket he had replaced the head as well with one from a PRE 93 model. the mechanic who did the work neglected to change cam sprockets so her car had a round tooth crank and intermediate sprocket and sqaure tooth cam sprocket and a square tooth belt.

she had put on 5000 miles on this setup with no loss of power of anything other than this odd sound and the fact the t belt was riding very close to the front edge of the cam sprocket.

i changed out the cam sprocket with correct one and replaced the belt as well with round tooth and the sound disappeared.

the point of all this is simple. these engines are so well designed and essentially in balance you can do some strange things to the timing setup and they will still run damn well in spite of it.