Does this look like it could be a front seal leak?
I checked the oil cooler seals and they're dry (replaced them anyway, torqued to 7 ft/lbs)
Push rod seals don't appear to be leaking, nor valve cover gaskets.

Thanks.

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Here's another view

Here's another view
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Most likely the front seal ,they get dry and leak in a used motor motor with some miles behind it.
Really you should clean it down as it is pretty crappy ,after a good clean you can put a piece of white cardboard under the motor and trace the leaks upwards,worked for me for years.
Works better with a warm engine however but not sure you are in that position ?.
Cleaning the case helps you find leaks and help it to run cooler hence the fins cast on the lower engine case.

I gotta go against the grain.

It doesn't look like a front seal leak to me. Oil is too evenly distributed and too far back on engine and case. Air from fan primarily blows from top down. Sure there is some leakage around the fan shroud but really not enough to blow oil that far rearward. Plus it is a very thin dirty film. Unless you cleaned the oil pump off, I'd expect to see a lot more oil directly below the front main seal if that seal were leaking.

Appears to be coming from above. Most of the oil residue appears to be older.

Can be a variety of sources:

Bad oil temp sender that is leaking - this usually runs down on oil cooler. Since you said those were dry I suspect this isn't it.
Could have been leaky cooler seals that someone replaced but didn't clean up the mess.
Can be weeping between base of cylinders and the case.
Can be bad PCV valve causing pressure inside case. Though this usually shows up as leaksage under the oil filler tower / breather assy at the gasket between the case and the breather.
Can be the gasket to the oil filter tower. If you have engine out and easy access I'd at least put a wrench on the nuts and/or replace that gasket while you have easy access.

Do agree that cleaning the case and monitoring it and/or using UV dye is best way to ID the source.

Agree, a good cleaning is in order. I took the photo in this state to see if anyone recognizes this type of mess. Thanks for the reply.

Superhawk996, thanks for the input.
I'll double check the sender.
I replaced cooler seals (previously) in '98 maybe 7k ago and cleaned entire engine then.
Cylinders look a little dirty and need to be cleaned - not sure what would cause any weeping between cylinders and block. Might just be oil blown by impeller.
It's a 76 so no PVC valve (breather vented to air box) but I note air filter seems a bit oilier than I would expect. The breather always seems to have a film of oil on the front side so it could be the base of the breather box.
Will definitely check/replace the oil filter tower gasket - good idea.
Yep, gonna clean it all up again.

Thanks,
Alan B

@TX914

Cylinder registers are known to deform over time and/or were never machined completely flat to start with at time of manufacture. Not enough to cause reliability issues but they will weep.

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I have two engines that were out of flat by about 0.004".

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Not enough to cause any sort of reliability issue but they were both showing heavy oil build up at base of cylinders at time of disassembly. I machined each by about 0.010" to returnt to flat.

Here is a partial cut still showing that more clean up is still needed

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And full cleanup at 0.010" taken off

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Also recently had a /6 Mag case machined by Ollies. Cylinder registers had "sunk" and needed to be welded up and then remachined to flat. Unfortunatly I had to pay for the /6 case work that I can't do for myself.

Very cool. What sort of parts washer do you own? Sparkly clean.

too much credit. Hot tanking is one of the things I trust my local FLAPS to do. $30 well spent to get major gunk off! Afterwards I still do several scrubdowns with S100 cleaner and various small scrub brushes to get it to that point.

@Superhawk996 Thanks for the explanation and pics. That is one clean case!
I removed the cooling tins in prep for cleaning top of engine. There was a light film of oil on top of the case at top of cooling tin but the oil pressure sensor switch is dry. Base of the intake runner is a bit wet/oily. Gasket or injector might have begun to weep a little. Cleaning everything and sent injectors off to Mr Injector.
Going to replace these seals while accessible:
- front seal
- oil filter console seal
- dizzy o-ring
- breather box gasket
- oil pressure sensor

I thought I'd have the engine out about a week to do engine bay seals and a few maintenance items... I've owned this car long enough to know better!

FLAP does the deed in house or farms out? Here, you're lucky if the oil disposal tank has room so you don't have to haul the still pretty full bucket home.

In house. FLAPS in front, machine shop in back. We are the Motor City afterall though I'm beginning to doubt that with transition to EV's.