I have an older 360 with low miles, 75,000. It was very original and leaked oil everywhere. I pulled the motor out and cleaned everything, added new seals and gaskets, along with new umbrella valve seals. I put it back together and it runs great but uses oil. I assumed my usage was leakage. The car smokes slightly on start up but doesn't seem to while driving, or so say my friends who were following me. The leaking is minimal now. So where is the oil going? It's been suggested that the valve guides may be bad, stuck rings, I'm not fouling plugs. I don't know where to look. Any ideas or magic you guys can share?

Did you replace the valve guide SEALS?

They usually get brittle and fall apart.

If you did and it still smoke on start up then I'd look at guides.

Yes I replaced the old seals. The reminded me of pecan shells. Very hard, broken up, and brittle. I bought seals and gaskets at the same time and the new valve seals were part of the stuff I bought. The new seals very unlike the old ones, resembling umbrellas. No more than it smokes, I can't see it being burnt. But it's not leaking. It's going someplace.

How much oil consumption are we talking about? When you can see smoke on start up, the valve guids can account for a quart in 1,000 miles by them selves. Enough oil burning to show up out the tail pipes is pretty bad oil use, it can burn a lot of oil and not be visible at the tail pipe. Do a compression test and a leak down test. Gene

Are any of the spark plugs shiny? If so look at two things to start with, intake manifold gaskets sealed up properly and or stuck rings or loose valve guides or both
If no shiny spark plugs look at the rings and guides first If it was a around town car with very little highway driving it may be stuck or gummed up rings or worn out due to being driven mainly when cold
As already suggested, do the compression test both wet and dry to see what that shows you

OK, I got some direction to go in. As for amount, I drove over 2 hrs to the mopar nats and used about 1/2 a qt. Ran great. Around town, short trips and such, it uses more. With cold weather coming on and not driving it as much, I should have time to do a compression check and a few other checks. Thanks guys.

My thoughts. I think the rings/cyls are worn especially the oil rings which might show bad on a compression test. the valve stem seals were that brittle after only 75K?? I think it has had a very hard life. EDIT meant to say "might NOT show on a compression test"

You can try heavier oil 20-50 wt or even 30-40 in summer unless you are racing and like work just add the oil. I have found most of oil uses on small blocks are poor intake manifold seal or the valve seals lifting up on guide and actually pushing the oil threw the guides. By the way try High mileage oil works great on oil leakers

Too many folks get caught up with the drama of lets rebuild it and fail miserably Car ran before and used oil, but ran, now its a hunk of crap in the garage waiting the scrapper. I saw a 70 firebird 400 that was painted but had a imperfect tint to owner who stripped it down again and left car in standard primer sitting outside 4 years rusted badly and scrapped it after hundreds of hours of body work. Whats that got to do with oil leaker? If you don't intend to finish car immediately leave it alone!

I agree. I'd rather it use a little oil and run good than open the lid on too big a can of worms. This motor is a 75 model and very original with exception to a cam swap I did while it was out. I had thought to try a different oil as that was a fairly inexpensive thing to try. Lots of good thoughts. Thanks folks.

Fwiw, my 77 Wagoneer is my winter daily. Its literally a fill the oil check the gas vehicle.

It burns a quart every hundred.

Doesn't worry me a bit as it doesn't ping and HSS good oil pressure.

If it's burning a quart every hundred miles you must have zero mosquitoes near you. I had a 63 BelAir that went thru a quart about every 50 miles, but it was a leak. Timing chain was so sloppy it wore a hole in the cover. But what do you expect for a $250 beater?

The 440 in my '67 Imperial would use a quart every 150-200 miles on the freeway, and it never visibly smoked. When it was rebuilt it was clear the valve guides were most of the problem.

I'm leaning towards the guides, it's a 41 yr old motor. I want to try a different weight oil first just to see what happens before I get too crazy. Thing is, with winter coming on, my window of experimenting is closing. I have this car for sale and don't want to sell it this way. It just runs too good to be anything serious, and not a big enough issue to warrant a full rebuild. I'm also leaning towards a set of the refurbished Aeroheads from Indy. $499 for new valves, guides, sprigs, decked and ready to go. Or, I'll just knock $499 off the price. That would fix the guide issue, if that's my problem, and give me some extras as well.

My 2006 Magnum with the 3.5 v6 uses a quart between oil changes. It has done this since new - and currently has 212,000 on it. I just add oil in the middle of the oil change mileage.

Pretty sloppy guides will seal with new seals for awhile. My bet is the intake gaskets leak or the oil rings are gummed up and stuck in the grooves.
Doug

Knock the $500 off the price. Installing new heads on a 75,000 short block opens up the chance of pulling oil up past the rings. Tell the buyer the car burns oil, most somewhat expect old cars to use oil. Gene

Stock iron heads and a stock iron square bore intake. I never even considered that my intake might be leaking. I'll look into that.