928 problem

[bennytech]

1985 928s lost compresion on 4 cylinders on left side,suspected head gaskets ,remuved and resufaced heads new gaskets,no visible damage,on pistons or valves,reinstall and still no compresion,,help

[Opelotus]

Is your 1985 928 a 16 valve engine? Or 32 valve? For one bank of cylinders to lose all compression, it sounds like a camshaft issue. If it's a 16 valve engine, look for a broken camshaft.

[honerboys]

i think the 32 valve is an interference engine - i think you would have noticed valve damage - broken/spinning timing belt sprocket on that side?? - or the broken cam ^^^^^

[honerboys]

there are woodruff keys on the camshaft - nos. 10 and 21 in picture - if they sheared it could cause what you're describing

[mch3jsb]

How did you verify no valve damage? Best practice I’ve found is when the head is off, set it up so you can pour some mineral spirits into the intake ports and see if it comes out around the valves, then repeat the same process on the exhaust ports. You can have valves that “look” good and still not seal.