Advice: S2 head overhaul Fulvia coupe 1.3S

[tool]

Thank you very much for very valuable answers.

I took a picture of the stud and the nut. I thought the stud might have an internal allen head, but I could detect it. I haven't seen a nut with a cut, like this one, so I was curious of the purpose.

I have used a "fuel stabilizer", that should contain a lead replacement, and cleaning additive, but I will look for a single purpose valve cleaning liquid. I have just driven 2500 km with the car, so the compression leak has probably developed over a longer period.

I will check the bolts carefully. As I understand from your reply, it doesn't make any sense to replace with reinforced bolts.

I will replace the valves, as you suggest.

Rgds
Tom

[Huib]

Wait a minute. There is a good chance there is a depositie on the valves caused by the additives.
Do NOT use any additives. Fulvia's run very well on unleaded. Stop using the additive. Try to clean valves by running the car on Euro98 from a reliable source. Run the car. If you like with a bit of engine cleaner. There is a good chance compression goes back to normal.