Did another compression check today to see if there was an improvement on cylinder number #1 after the approximately 550 kilometres I drove the car last weekend. With all spark plugs removed one thing that became clear immediately was the fact that, compared to last Saturday, they were all closer in colour. But with #1 still being notably richer, all four are (far) to lean.
The compression test itself didn't reveal anything new, with #1 still approximately 20% lower compared to the other three. As I did have an assistant this time we noticed that #1 needs a few extra piston strokes to built up the pressure compared to the other three. This might point to a small leak somewhere. On the other hand it shouldn't be that much of a surprise. The engine actually performed pretty well since it was installed well over 17 years and 110.000 kilometres ago. And most of those kilometres have been pretty hard, with the best bit probably being a blast up the Stelvio in the summer of 2002 in a little over 15 minutes (yes no traffic at all), with the engine constantly between 5000 and 7000 rpm in first, second and third gear.
So time to stop tinkering and pension of the engine, or go for a complete overhaul. I had hoped I could use this engine with some minor work for the FHC I am currently restoring, but that isn't to be. But I did have some foresight here, as I already have been in touch with an engine builder for a new and more powerful Sprint engine for 't Kreng (aim is ±220 BHP with a rev limit around 8500 rpm) and this work was scheduled for next year anyway.
But I will probably first start with removing the head, maybe it is something simple like a sticky or burned valve. And did I mention the carburettors need a full service? As you can see in the picture above #1 is clearly richer compared to the others. And this carburettor barrel used to feed cylinder #3, coincidence? At least I don't need to worry I'll bore myself to death this winter ...