Our 912 engine has been a real mess lately.
Its always run a little rough, lots of spitting, popping, backfires... we thought it was ignition so we went with Pertronics and a new coil.
The Solex carbs were giving us trouble so we swapped in a set of Delorto's. We found a leaky accel jet, bad float bowl adjustment, and we made sure to swap in the correct main jets.
After all that, it never ran worse. The car was undrivable. The syncrometer said that the back throats were pulling much less than the fronts, on both sides of the engine and a compression test showed the passenger-side back cylinder was ~90psi where the others were ~120. I decided to pull the motor and pull off the heads.
So here we are, heads are off, and pulled the exhaust valve out of the passenger side rear and it looks fine, not fried. It does look like the valve guides on the exhaust valves are starting to leak, but other than that I can see no issue. Note that each head has an exhaust valve that is dark and one that is tan. Also note that the 2 of the pistons have shiny clean areas where the other two are full dark. I also noticed that the cylinders had just a touch of scoring and i can clearly see a cross-hatch pattern, like someone took a grape hone to them.
I honestly don't know what to do from here. Im planning to hot tank the heads and get them all cleaned up, but where do I go from here?
Thoughts? Suggestions? HELP!
Pistons: Mahle 82,46
Intake ports: roughly oval 32x34mm
Engine code: 32984 729/1
