Pressure

[Mudtub]

Why is there crankcase pressure. cylinder 1,2,3 are 120 psi, #4 is 110. oil vapor, pressure also in or coming from valve cover. What is going on? Thanks

[I Leak Oil]

Why is there crankcase pressure. cylinder 1,2,3 are 120 psi, #4 is 110. oil vapor, pressure also in or coming from valve cover. What is going on? Thanks

Did you forget what you started here?????
http://www.roversnorth.com/forums/showthread.php?t=10063

Did you do a leak down test? That will atleast isolate the cylinder(s) that are problematic. You'll most likely need to start tearing it down to find out anyway.

[Tim Smith]

I'm in the same boat as you. I haven't done the leak down test as I'm now 110% sure my rings are shot. I've been chasing the crankcase vapor for a long time and if memory serves, my compression numbers were about the same as yours.

I did try the Marvel Mystery Oil trick which gave me some boosted performance and a couple of thousand more miles of burning *less oil than before but now it seems I'm back to where I was six months ago. If you want to avoid tearing into it for a while, try it for your self. I can't see any harm in adding a quart of MMO to the crank case for 500 miles. If there is possible harm in this then some one tell me know. I've been advocating this for the last six months or so and would hate to point someone in the wrong direction.

In the end though Mudtub, you'll probably be looking at a ring job at the least.

[Mudtub]

so we brought #1 to TDC and put some air to it, she did not hold pressure. added oil, all kinds of pressure. So she needs rings. what is the best way to replace the rings? total rebuild or can it be done without removing the head. remove the pan and go from the underside. thanks again

[Tim Smith]

I presume you want to do this with the engine in the truck.

You will need to pull the head and the pan. Undo the connecting rods and pull the pistons out the top. Hone out the cylinders, place new rings and then insert the pistons back again through the top with a ring compressor. Clean off the crank shaft and the cylinders of any debris from the honing before reconnecting the con rods or placing the pistons back in. Reassemble the head, con rods and the pan with the con rods being first on the list. Then you are all set for your first startup after reconnecting the down pipe and carb.

Only special tools needed are a hone and the ring compressor but those can be gotten at just about any decent parts store. It can be done in a day if you have the tools and parts on hand and don't get stuck with little details like why the old rings won't come out without a punch. You can leave the header and intake manifold in place for this job but make sure the down pipe nuts will come off with liberal amounts of PB blaster for a few days before the job.