sump tank pressurized

[66-68shelby]

My oil tank pressurized on my 68 2.0 and pumped oil into my air cleaners. I did a leak down and #5 was leaking 50% in to the crank case. All other cylinders within 10%. Pulled motor down and found no problem with the rings or piston in #5. The rings were free, not broken, and no crack or hole in piston. Pistons and cylinder within spec. Made a steel plate to seal head and pressurized combustion chamber. No crack or leak in head was found. Engine was rebuilt by someone about 1500 miles ago. Had bad ignition and jetted too rich when I got the car. Driven about 300 miles since jetting to factory specs. and adding MSD. Piston tops and combustion chambers full of carbon. Am I missing something here? Really don't want to finish rebuild without finding a cause of compression loss.

[911quest]

If it was running rich it probably washed the cylinders down with gas and the rings never seated.

[Gearbox]

Check oil level, you may have it a bit too high. I had to keep the level just on the tip of the dip stick to keep it from filling up the air filter when hot. Gauge reads 6-7 quarts.

[66-68shelby]

Thanks for the replies. After the first time the oil pumped out oil was at at bottom of dip stick. Cleaned engine and exhaust up and drove 5 miles and it pumped so much oil out I thought it would catch fire. Still searching for reason.

[Eric911S]

Hello: How much oil do you have in the system? Sounds like you may have overfilled it. Thanks Eric

[66-68shelby]

When both sump and tank were drained it was 10 quarts. Still trying to find reason for 50% leak down in #5.

[Eric911S]

Hello: On your #5 cylinder where is it leaking from? Exhaust=exhaust valve, intake=intake valve or out of the oil tank or top of engine=rings or cylinder. If it is leaking from the valves loosen them off and see if the leakdown changes. If it still is leaking from the valves you may have carbon under the valve seat or a bent valve. If it is carbon tap the end of the valve with a hammer and let it pop back. You have to remove the rocker to do this right. If it still leaks from the valve then you have a burnt or bent valve. Hope this helps. Thanks Eric

[66-68shelby]

Thanks Eric. The valves on number 5 we fine. The air was going into the sump tank. I did have ongoing carbon under the valves. The pistons, cylinders, and exhaust ports were packed with carbon. Looked like an old Onan 2 cylinder RV generator that had never been decarboned.

[911pcars]

"Still trying to find reason for 50% leak down in #5."

During the leakdown test, if you leaned real close to the oil filler tube and felt your hair wave in the breeze, then it's no. 5 piston/cylinder.

Take no. 5 to someone who can visually inspect. Sounds like the rings didn't seat, rings installed upside down, wrong size, or something. Did you put this back together after inspecting? Could have tried new rings and scuffed the cylinders if smooth.

Sherwood