I put a vacuum pump on my motor and the max vacuum it would pull was 3 - 4 inches. I called the manufacturer and he said based on where I have the pressure relief set it should be making 25 inches. Obviously I have a major leak.

So I smoked the motor and discovered that my awesome indy billet rear main seal cap was the culprit. I pulled the engine to reseal and the smoke no longer comes out around the cap but it is sneaking out past the actual top half of the seal. I am hoping that will seal up a little better when the engine is actually running but i guess we will see.

Any hints or tips on sealing up a big dodge for a vacuum pump???

WE install our rear main seals backwards.

I have heard that. I just did not have the cachonies to try it!

I did it on my SB... but the seals now days
you can get away without doing it... unless
you pull big vac and you dont want to do that
because it can pull oil from the wrist pins..
the most I ran was 14"hg.. I could pull that
much with just the dry sump pump

my rear main seal is installed the std way around. i have 5" vac on idle cold with an aluminium block. when my rings were tired my vac was low but on a fresh build its all good.

So how many inches of vacuum should you run an engine at? Aerospace says 10/12 is where it should be so who is telling you 25?

When I talked to Reher-Morrison(sp) they said 14"-16" max
for what we do(we dont pull the engine down every 5 runs)
I was normally max of 12"-13"... understand thats inches
of merc (HG).. thats a lot of vac
EDIT
run 25"HG and you will crush a 55 gal drum into
a pancake