Oil Leak! HELP!!!!!

Iron block sbc. Changed the rear main seal 4 times pan gasket 6 times 3 different pans. Keeps leaking in rear near the back bolts and in the center of the pan saddle. Crank is dry. Brand New crank by the way.
Tried both the one piece felpro and the old cork style.

Also unbolted the tranny and checked the cam plug and restictor plugs. All dry

Checked for excessive crankcase pressure nothing out of breathers also pulled the blower and manifold and re checked intake gaskets. OK. Also checked compression and leak down. All cylinders at 1 percent #4 leaks a little more but nothing bad.

Any ideas? I'm pulling the rear main cap
and magnafluxing it tomorrow.

 

350 are 400 main size? If it's a 400 that has been align bored are a aftermarket 400 block, felpro has a different part number.

 

I know you stated three different pans were tried--- I always tried the pan on the block without the gaskets first--- to assess the quality and fit of the pan--- alot of manufactured pans are crooked , twisted.
Sometimes they could be fixed, sometimes they were sold or trashed ---

 

It's a 350 block.

I have noticed the difference in pan rails but it's real hard to determine the saddle area. All three pans are different there.

In case you're wondering why the 350 block. It's kind of a training motor while we get another trans. We have a real nice piece on the stand waiting to go in but the trans we have won't hold it and my driver is very green. I want to take baby steps first.

 

Are you using a "glue" to put the deal over the rear cap, or silicone ?

 

Over the rear cap? I'm only using silicone. I put some on the block cap mating surface near the rear seal and a few dabs in the corners where the tits of the gasket fit along side the main cap.

 

Trying using a glue to hold the seal firmly on the cap when you assemble the pan onto the block--- give it time to set up---- using silicone to keep a seal in place lets it move .
Try a 3 M weather adhesive or a permatex glue ----

 

Thanks, Mark. I'll try that.

 

OK - this is a very crude way to fix it but worked for me....I put a 502 crate motor in my 1969 Chevelle and swapped pans to fit the A-body....darn think dripped just a little and I was trying to avoid lifting the motor to replace the gasket...
Bruce at Advance Transmission in Knoxville, IA mentioned that he worked at a Chevrolet dealer in the late 1970's.....they had rear pan leaks on Monte Carlos and after multiple warranty pan and gasket replacements he made a tool to reform the rear pan rail around the main cap....
I went to the hardware store and bought a very large chisel....rounded it off to fit the rear pan contour and pushed the pan rail tight to the gasket with a hammer and the home made tool....had to also beat on the lip just a little to "roll" the rail into the gasket....worked like a charm.....no drips!

 

you could also check the 3/8 bolt hole at the front by where block off plate for fuel pump goes. I have seen the oil run out there along the pan rail and out the back of the motor. Could also explain the leak in middle.