Fuel in oil.

With maybe 15 passes on it, the oil in my heap is pretty murky looking and has a distinct smell of gas. Is this a sign that I might still be way rich (76 primary, 84 secondary in a 780), or am I finally to a point where there's enough blow-by that I just really need to plan for a tear down? Compression is great 205-215 psi cranking pressure, cold.

If you're concerned about compression, do a leak-down test and check your fuel system, especially if you have one of the cheap fuel regulators. I had one that had a leaky diaphragm that ended up with approx 1 qrt of race fuel in my crankcase. The day before going to a test session I had a very hard start and even though I kept smelling gas, I hadn't done basic inspection (look down the throttle bores with the electric pump running) and almost hydrauliced (sic?) a cylinder. The next day I noticed bubbles coming out of the front corner of the oil pan (crankcase pressure) and oil on the trailer deck! So much for that test session, back to the shop! The following day I drained the oil and noticed not only the strong odor of fuel but it was also diluted with gas in the oil pan; glad I didn't make any passes on that fresh engine! Needless to say, I pulled the engine and discovered washed bearings, scuffed cylinder walls but saved myself a big bill from catastrophic engine failure...it's always the little things. Not saying anything about your situation other than, make sure of what you do know so it doesn't bite you!

The jetting seems kinda big for a 780 Holley.

If you have a mechanical pump, I’d could have a diaphragm that’s failing and letting fuel pass through it.

If electric, what’s the pressure set at?

Electric pump. 7-8 psi.

Drop it to 5.5 to 6psi.
Secondaries seem too rich. Check your #5;6,7,8 plugs

You would have to have a massive issue in the motor for unburnt liquid fuel to get in the oil from the intake system

I don't have a power valve on the secondaries, hence the staggered jetting. I think I'll drop two more, and see if anything happens. Cab, are you thinking just regular blow-by? I haven't leak-downed this thing in a while. Last time it was around 8%, and that was probably 60-70 passes ago.

x2

Check your float levels in the carb. If too high it will continue to dump fuel into the intake after shutoff.

Also check needles and seats. Turn on fuel pump with engine off and look down carb to see if there's any dripping. After you shut engine off after a pass there is still pressure in the fuel line, it will drip quite a lot of gas into your engine. Gas drips into intake and then finds an open valve.