I've got a '73 460 that was originally in a Lincoln. It's in my 1988 F-350 (and has been for 15 years). I don't know the mileage on the engine, but I would guess around 100k in it's lifetime. To my knowledge, the crank, pistons, & rings have never been touched. It burns oil in one cylinder (#3). All of the other spark plugs burn clean and look yellow/tan like they should, but one cruds up really bad from oil. The only time I see it smoke is when I start it (only when sitting for at least 15 minutes), or just slightly after sitting and idling at a traffic light for a few minutes. Never smokes on acceleration, hard or soft.

It burns about a quart every 750-800 highway miles or every 600 50/50 city/highway miles. Consumption hasn't seemed to get worse since I've owned it (almost exactly a year, & 8k miles). I'd guess that all of the cylinders burn a little oil, but they're all at acceptable consumption except for the "problem cylinder." The bank of cylinders 5, 6, 7, & 8 never smokes at all, not even a little (I can tell them apart with my dual exhaust).

I've replaced a few valve guide seals on the bank that has the "problem cylinder." Haven't had the time to do all of them yet (since I drive the truck every day), but I got to replacing the take and exhaust valve seals on cylinders 1 & 2, and I did the intake seal on #3 (the oily cylinder). Most of the seals came out okay and still had some rubbery feel to them but were a little on the hard side.
The worst one so far was the intake valve seal on cylinder #3. It fell out in 3 pieces, and was hard like plastic:


I hope to replace the exhaust valve seal on cylinder #3 soon to see what it looks like. It may be contributing to oil burning if it's as bad as the intake seal.

Haven't done a compression check yet to see what it says across cylinders. I'd guess the compression is still fairly decent on that cylinder, because engine RPM drops exactly the same when I unhook that spark plug wire as when I unhook any other plug wire.

Other than the oil consumption of that one cylinder, I can't find another thing wrong with the engine. It's just one of those little things that bugs me.

What would you guys do in my case? Prepare for swap or rebuild? Just keep running it? Any other ideas? Could it be a head gasket issue (doesn't use any coolant, & no oil in coolant)? I don't think that much oil could be slipping past valve seals, but I also don't know why that piston ring would be giving any trouble when the rest of the cylinders hardly burn any oil at all.

I'm halfway thinking of getting another 460 to build and have on hand incase this one goes further south.

I can post video of the oil smoke on start up, and no smoke while running/accelerating if it would help you guys give me advice.

I need some opinions...

 

Well, one thing that I rely on that is a simple way to determine engine wear and how "good" everything is still sealing is blowby. Cover all but one hole in the ventilation of the engine and see how much it is ouffing out of the crank case. If none, or little, then I assume your engine is still doing what it can, if a lot, you have a problem.

Next is a compression check. See what this says.

If by now you have found no problems, check oil pressure with a good gauge, if good, then keep driving it , or I would at least.

If a lot of blowby, you know compression is escaping and going out the bottom or into the valve cover.

Low oil pressure, bad bearings

Compression, low bad valves/rings/cylinders/head gaskets

Run a fewtests and see what it yields. Watch for symptoms other than the oil that lead to worn out engine.

 

Blowby is not bad at all. Hardly any.

Hoping to get this done tomorrow. I'll report back on the results.

Oil pressure is at:
60 PSI cold @1000 RPM high idle
40 PSI hot (running for at least 20 minutes after some highway time) @ 1000 RPM, & add about 5 PSI per 1k RPM.
About 25 PSI hot @750 RPM (normal warm idle)
Oil pressure is solid, not jumpy at all

Like I said, I see no signs of wear other than this one cylinder that burns a lot of oil. A quart to every 600-800 miles is a lot when only 1 cylinder is doing most of the burning... It smokes a lot from that cylinder on startup. I'll try to post a pic of the spark plugs when I take them out for compression testing. Like I said before, 7 of them burn nicely and the other one will crud up really bad in 1,000 miles.

Also, there's a "ticking" noise that seems to be originating from that cylinder. Not a knocking noise, just a light tapping noise (like valve train noise).

Could it be one bad ring? I don't really mind pulling the engine to replace it. I don't know too much about the history of this engine. I know that there was a new camshaft put in it (high torque "RV" cam) and an intake put on it 15 years ago, and I think the guy did what he considered a "rebuild". Not sure what the "rebuild" consisted of. Not sure if he did bearings or rings or if he only messed with the top end. I'm starting to wonder if he installed a ring wrong and he either never worried about it or it just failed after a couple years. I'm the 3rd owner since the "rebuild" of this '73 engine. 1st was the guy that "rebuilt" the engine and swapped it in (I've never talked to him, though I'd like to find out who he is), and the 2nd guy said it burned oil in that cylinder the whole time he had it. The guy who swapped the engine into the truck ran Cam 2 race fuel in it at 104 octane, not sure what his purposes were with the truck but it's pretty dang fast on just 93 octane with the little 600 CFM carb I'm running.

 

Got the compression check done:
#1: 161 PSI
#2: 150 PSI
#3: 155 PSI
#4: 160 PSI
#5: 158 PSI
#6: 160 PSI
#7: 152 PSI
#8: 158 PSI

Seems pretty decent to me