Engine:
87 305 LB9, 110Kmiles, as far as I can tell stock.

It’s clearly burning oil, but only when it’s warm/hot, and the only time you really see it is if you let it sit running but not moving for a few minutes and then pull off, none of the typical puff of smoke at startup, when you go to coast, at WOT, or blow by (no chugging out the oil fill cap), at least not enough to notice.

Even stranger, I took it to the track a couple of Fridays ago, and after a few passes it seemed to stop burning oil, and AAMOF, I drove it a hundred or so miles since then before it started noticeably burning oil again.

The only other thing to note is that it has what I think is an exhaust leak, a ticking noise that you can clearly on the driver’s side, only under load (a tick can be a lot of things, but usually you hear it at idle/all the time if it’s valve train or bearings).

Anyone have a guess what’s causing the oil burning?

 

It's probably valve stem seals.

 

What do the plugs look like?

How much does it use?

Maybe time for compression check?

High cylinder/ring loads (track) would tend to seat or unstick the rings.

A qt of atf in the motor oil would help stuck rings.

 

It seems like half the answers I get are “valvestems” but for the life of me I couldn’t explain the symptoms that I’m getting if it was valve stems. OTOH, if you give me a good reason I love that answer since I originally bought the car to swap another drivetrain into but after seeing a reasonably well running 305 I decided that I’ll make the 305 run fast first, and I have another set of stock heads sitting around, so that would be an easy solution.

Stuck or a broken ring has crossed my mind because of the fact that it changed, but again, I don’t know that I can explain the rest of the symptoms. I would have expected to see visible blow by out the fill cap if that was the case.

How much oil? Donno really, the car is new to me and I haven’t even done an oil change on it yet, same with the plugs. Don’t have a compression tester but I do have a leakdown tester, and I’ll probably give that a try if/when I get around to pulling the plugs.

To be honest, I was hoping for a “I know exactly what that is,” or a “my car did that,” since if it’s rings, a ring land, pretty much anything in the bottom end I might as well not even waste my time diagnosing it and just pull it.

 

All the bad valve seals that I have ever had, always gave a little puff when starting. Usually it had to set for a day or so. New seals and/or guides fixed.
These were some high mile 350's, carbed and 100,000 plus.

The only broken ring symptom was high vacuum smoke, like get on it, rev high, then just lift the gas peddle. Looked like fogging for bugs. Big ridge on cylinders, it was a cobbed up motor.

Had a 4.3 vortex that sucked oil up past the intake bolts. It gave a big puff of smoke at start but at random. Changed the intake gaskets and sealed the bolts, all was fine.

I would still try the atf, "it won't hurt anything" (sofakingdom) just might help. If that car had been babied (little ol lady) stuck rings are a real possiblity.

Is there any gunk that you can see inside the valve covers?

 

Won’t hurt anything….

You know, I’ve never actually tried it, I know the reasoning (the fact that ATF is much heavier in detergents than any other lubricant and is a reasonable weight for something to be in the crankcase), but never had anything that I felt needed it.

Anyway, looking in the filler, it’s not _that_ dirty, I mean, it’s not clean like the cars that I’ve owned from new and have always had mobile 1 or other quality oil in them, but not dirty like it hasn’t been maintained, somewhere in the middle.

Anyway, I had some conventional mobil ATF and dumped a quart in and went for about a 1/2hour drive, the whole time, nothing out the exhaust, no smell of oil burning. Parked the car, went inside, came back out about ½ an hour later (still warm but mostly not hot at all, warm day), started it… holy crap, big cloud of smoke, something on the order of almost as bad as running some top end cleaner through the car and restarting it (might not have been _quite_ that bad, there was a bit of an embarrassment factor considering I was at a shop that I used to work at, but it was a BIG cloud of smoke). The next few stops that I pulled away from, another good size cloud of smoke, which gradually got better and went away by the time I made the roughly 40minute trip home.

I’m not sure what the deal there was, the strange thing was that I didn’t smell the oil smoke in the exhaust like I did before, and that smell hasn’t come back since the track. I also didn’t get a chance to pull any plugs, just as I got home and got the hood open it started raining.

Man, this is getting more strange the longer/more I think about it…

 

Wasn't a SBC, but I had one that never puffed on start-up, but sit idling at a stop light, and it would kill all mosquitoes in a quarter mile radius.

Had the head worked, including new seals (guides were fine), completely fixed the smoke and oil consumption issues.

 

Sorry about the embarrassing moment.

ATF will smoke more when burned. I seem to remember when that TH400 modulator valve ruptured that there was a lot of smoke while the ATF was being sucked into the engine.

I would pull the PCV valve, out of the valve cover and see if the smoking changed. There are only a few paths for oil to get to the intake.

The guides in one of those engines was worn to the .010 mark. Still just a little puff on start.