help rquired mk1 golf gti

hi if anyone can help it would be very much appreciated i have got a mk1 golf gti 8v k-jet car is running slightly rough i have had timing set it is spot on changed the usual thing new plugs,leads dizzy coil pack but still the same but when car has been running for a while i took oil cap off top of engine and alot of air come out has anyone had this before or does anyone know what the cause could be got told it could be head gasket or could need new piston rings can anyone help thanks craig

If the oil level is dropping, and smoke out the exhaust, it is possible that ring.

injector test and/or compression test would get you started

done a pressure test and he said seems ok but did a test on engine block and he said that there is 80% leakage and he said could only presume that it is leaking through piston rings

That's what I thought, now it's starting to open the head and block and exchange rings, and exchange takes the valves retainers and other fasteners that are resected by chance.

Most 1.8 gti engines breath heavily....if you can smell exhaust fumes then you may have a ring issue, I would be more inclined to spray easi start at the back of the engine where the injectors are and look for possible air leaks....

anyway, if air leaks will have to open the engine to replace the gaskets. So I'd already opened it all at once, changing the ring and possible leaks, and all seals that can be resected and old …