I just rebuilt my 87' f-250 460, I used as follows:
Mellings oil pump, TRW Forged pistons, 9.2-1 comp.,
Edelbrock rpm heads, comp cams extreme 4x4 cam, lifters,
pushrods and roller tip rockers, stock intake, stock holley 600 carb with lighter secondary springs and a little richer on main
and secondaries, K&N airfilter (stock replacement) sealed power gaskets, and 21/2 dual exhaust out of stock exhaust manifolds into flowmasters 40s and out ( no cats). I have 500 miles on the motor and I notice a very small lek coming out of the rear main seal, I chcked the back of the manifold and oil sender so I Know it is from the rear main, When I installed the 2 peice seal I made sure to put gasket sealer on both sides of the cap corners
and a little more up to the seal, but not where it butts, I then
left a little of both sides up out of the seat on opposite side of the cap and block just like the manual said and I checked ten times to make sure the seal was not in backwards and I also lubed
it with oil before assembly, now after all that you would think this thing wouldnt leak! but it does,not at idle but above 2500
rpms, I did notice that my dipstick comes out a 1/4 inch after
I take the truck out which indicates a lot of crancase pressure
but I have all the stock pcv in place and it works, I also used gasket sealer on both the cam freeze plug and also the oil galley plugs. The truck reallllly hauls, but I can't figure out this leak, maybe the rings haven't broken in yet and I am getting blow by? But I do'nt notice any oil burning. If any of you people can figure this one out I really would appreciate it>
Thanks Lee

 

I am not an expert so fair warning. I do like the Melling oil pumps, used them on an old D#$%# B engine way back. Did you use the high volume or high pressure pump? Probably wouldn't make a difference on the rear seal, but like I said, don't know Ford engines that well. High pressure pumps occasionally will cause leaks and blow out seals, I prefer the high volume pump, besides I am pretty sure you can up the pressure of any pump with just a different spring.

I think your thought about crank case pressure is probably the clue. I would break in the engine for perhaps a thousand miles and then check to see whats up. BTW did you grease up the crank journals and the seal when you installed them? You can develop a leak if you run the seal dry for any length of time.

Did you use a fresh PCV and did you put it in the right direction? Dumb questions, I know but I have been known to do dumb things so it doesn't hurt to ask. You might want to look at getting a tighter dip stick if it keeps popping out.

Good Luck.

Jim Henderson

 

Thanks Jim,

I really hope it is crankcase pressure from blowby, but you know,
every time I get a leak, be it cars or plumbing in homes it always gets worse, it just hits home when you get everything perfect and then the worst seal to replace leaks, and after you know it is a potential problem and try to take evey precaution.
well I guess the worst thing is that sometime this summer I will crawl under this truck, remove the motor mounts, jack it up,
take off the pan and rear cap and fix it! I reaalllly hope it fixes it self! Thanks for the reply, Lee

 

Since you did such a good job on the seal installation, I'm wondering if maybe it might be the rear oil pan seal. Just a thought.

 

>I just rebuilt my 87' f-250
>460, I used as follows:
>
>Mellings oil pump, TRW Forged pistons,
>9.2-1 comp.,
>Edelbrock rpm heads, comp cams extreme
>4x4 cam, lifters,
>pushrods and roller tip rockers, stock
>intake, stock holley 600 carb
>with lighter secondary springs and
>a little richer on main
>
>and secondaries, K&N airfilter (stock replacement)
>sealed power gaskets, and 21/2
>dual exhaust out of stock
>exhaust manifolds into flowmasters 40s
>and out ( no cats).
>I have 500 miles on
>the motor and I notice
>a very small lek coming
>out of the rear main
>seal, I chcked the back
>of the manifold and oil
>sender so I Know it
>is from the rear main,

i don't understand your problem. you answered your own question, if you know it's the rear main, fix it.