I have a slightly rough running 306 with about 5k miles on the build. I recently pulled plugs and found #3 to be black with some oil on the piston when peaking in with a borescope. Engine does seem to consume a bit of oil and I do run an oil separator that picks up a small amount, but upon removing the upper I see a fairly dry intake tract. No oil puddle in the plenum and just the smallest trace of oily film in the lower runners. Prior to removing the upper I did a leakdown test and all cylinders were between 4 to 9% loss. #3 was 7% so no smoking gun there.
I checked the torque of the lower intake and some bolts were about 1/2 to 3/4 of a turn loose, so I thought perhaps it could be a leaky intake gasket. I torqued it back down and was going to botton things up but thought I’d take a peak under the valve covers.
Some witness marks look ok, but a few show signs of a valve rotating with 2 distinct lines forming an x, and #3 exhaust shows no distinct line at all. When removing rockers and pushrods for inspection, they all look good with no wear or contact marks, but when pushing down on the roller lifters (Ford H version) with a pushrod, all will collapse except #3 exhaust. It is either pumped up and not releasing, or is bottomed out.
Is there any relationship to this possible failed lifter, and oil in the cylinder. I’m not connecting the dots here.
Next step is to remove the lower.
For reference, the build is a stock block bored to a 306, Ed cam, AFR165’s looked over by Ed, Tmoss’d Explorer lower, 30lb injectors, Quarterhorse tuned by Decipha.
Thanks.
I checked the torque of the lower intake and some bolts were about 1/2 to 3/4 of a turn loose, so I thought perhaps it could be a leaky intake gasket. I torqued it back down and was going to botton things up but thought I’d take a peak under the valve covers.
Some witness marks look ok, but a few show signs of a valve rotating with 2 distinct lines forming an x, and #3 exhaust shows no distinct line at all. When removing rockers and pushrods for inspection, they all look good with no wear or contact marks, but when pushing down on the roller lifters (Ford H version) with a pushrod, all will collapse except #3 exhaust. It is either pumped up and not releasing, or is bottomed out.
Is there any relationship to this possible failed lifter, and oil in the cylinder. I’m not connecting the dots here.
Next step is to remove the lower.
For reference, the build is a stock block bored to a 306, Ed cam, AFR165’s looked over by Ed, Tmoss’d Explorer lower, 30lb injectors, Quarterhorse tuned by Decipha.
Thanks.
