Okay, I put over 100 miles on the new 428. Everything seemed fine. Then it started missing and smoking a bit. I found the two rear plugs fouled. It's also used about 1-1/2 quarts of oil. The break-in smoke had stopped some time before as the rings seated.
I suspected an intake leak so I checked the bolts. 3 of the 4 rear bolts and 1 of the front ones came loose with less than 10 ft/lbs. The other bolts were slightly tighter. Okay, so I thought that must be it. The rear cylinders were sucking oil into the chamber from the valley. Changed plugs and tightened down intake to 30 ft/lbs. Motor starts and has no miss. Still smoking lightly, though. I take the car for a drive and after a few minutes it's really smoking again.
At this point I did a leak down test and compression test on all cylinders.
Leakdown was 3-4% for all cylinders. Sounds great so far. Cranking compression was 185-195 psi on the front 6 cylinders, but 212-215 psi on the rear two cylinders. Kinda weird, but I thought the rear two cylinders might have some oil in them which would affect the cranking compression?? Also, checked valve lash on all cylinders. It was A-OK.
Okay, so now I'm thinking short block is fine and I'm either still getting oil past the intake gasket into the rear cylinders or maybe it's coming down past a valve stem seal. Kinda weird it would happen on the back two cylinders at the same time, but who knows?
I took off the intake expecting to find some tell-tale sign of leakage at the intake gasket and/or in the intake ports. Everything looked fine, though. The gasket was positioned correctly and didn't have any obvious place it was leaking. The cylinder head ports look very clean as does the valve stem. Now I'm confused.
It could be that oil was in fact leaking past the intake gasket, but the only evidence is lightly torqued intake bolts.
Could I have overfilled the oil pan? I put 8 quarts total (7 plus filter)in my Milodon pan. I now think 7 total is correct. Could oil have backed up in the shallow back part of the pan and got into the rear cylinders from below?
Where else could oil be getting into the rear cylinders?
Any thoughts or ideas appreciated,
Paul
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