oil leakage question

[TrollFromDownBelow]

She doesn't leak (or I guess more accurately, drips) driving her around town, short trips, etc.However, if I'm on the expressway driving her at 65 mph for an hour or more, I'll get a nice sized spot (about the size of a big silver dollar) at the front of the engine .... I'm guessing the main seal (Colin and I replaced this about 4k ago). It's weird how it doesn't leak/drip otherwise.... even after a 32 mile hwy trip from work won't do it. Any suggestions?

[Amskeptic]

She doesn't leak (or I guess more accurately, drips) driving her around town, short trips, etc.However, if I'm on the expressway driving her at 65 mph for an hour or more, I'll get a nice sized spot (about the size of a big silver dollar) at the front of the engine .... I'm guessing the main seal (Colin and I replaced this about 4k ago). It's weird how it doesn't leak/drip otherwise.... even after a 32 mile hwy trip from work won't do it. Any suggestions?

That is much more a gallery plug symptom, leaking only under full pressure ....
Colin

[TrollFromDownBelow]

I'd much rather it be a galley plug than a main seal .... it means that the lower end is good, and I can proceed with my top end rebuild with new heads. :)

[Amskeptic]

I'd much rather it be a galley plug than a main seal .... it means that the lower end is good, and I can proceed with my top end rebuild with new heads. :)

Not so fast. Your lower end will tell you if it is good only after both crankshaft and camshaft endplay checks and a plastigage check of the rod bearings and a visual on the cam lobes ... Gallery plugs that have loosened can cause catastrophic engine failure within a second or so at highway speed. The proper repair involves drilling and tapping the gallery plug hole which must be done with a fully split and disassembled case.
I got off with an Idiot's Free Pass in Winnie Texas when I JB Welded the fallen off gallery plug back into the case, but ... the engine was mortally wounded.
Colin