I've been trying to get my oil pan to fit my block, I've been testing 2 gasket types (1 piece, and traditional), and 2 oil pans (Original 3 tab and Canton). The original pan and a traditional gasket has been used on this block before, but I had to remove to fix an oil pressure issue. When putting the block back together I noticed that the original pan did not sit flush, it rocked diagonally from passenger side rear, to driver side front by about 1/8th in.. So I tried to gently massage it to fit, and no change. I ordered a new pan and 1 piece gasket. Here's the results of what I've got. Looking for recommendations.

1. Original Pan + Traditional gasket: Rear seal fits tight, but I can slip a .01 gauge between a couple of areas.

2. Original Pan + 1 piece gasket: Rear Seal gap is .022. I can also slip a .01 gauge between several areas. Also, very difficult to get the holes to line up between the pan, gasket, and block.

3. Canton Pan + 1 piece gasket: Rear seal gap is .056. I can visibly see between the rear main cap and gasket. I can also slip a .01 gauge between several areas.

If I use some gasket sealer, (ultra gray, or ultra black), will the original pan and traditional gasket seal?

Let me offer some advice straight from BOP about the 1-piece gasket.

But first I have to assume that these measurements you speak of above are with the pan and gasket just sitting on the block (upside down) or is this with the bolts in and snugged down????

Anyway - BOP says glue the rear section of the 1-piece gasket to the oil pan using super weatherstrip adhesive. The curved rear section is the only part without the metal reinforcement built in. I found that I had to carry the glue past the 1st back corner bolt holes. Painters tape to hold the rest of the gasket to the pan was also helpful.

Then snug the pan to the engine with the bolts (snug, NOT fully torqued) and wait 24 hours for the glue to dry.

Then remove the bolts, apply a dab of silicone in the rear corners where the rear bearing cap thrust block meets the pan (where the oil pan seals to) and then bolt the pan on and torque down the bolts.

All tests done were done with the pan bolted and torqued appropriately down.

Something is totally rotten in the State of Denmark! An object (like maybe the oil pump pickup tube) is holding your pan away from the block.

I was using a Milodon stock replacement pan.

I does not appear to be, I've checked the pickup tube and I have 3/8 in. clearance. I'll have to recheck,

Could the pickup tube be slighly off and hitting internal pan baffles?

I don't believe so. Right now I'm on travel, so I can't go out and re-check. I'm adding it to my list though. I took great care when installing the pump and pickup to ensure nothing was in the way. But something is obviously amiss.