OK, I am going to play real stupid. I have been using a little oil in my 460 which is a 18000# motorhome. However yesterday, I went for a 150 mile ride and I really used some oil. I checked the oil before I left the house and it was full.

When I was on the freeway, I turn 3250 RPM to run 60 MPH. I used 2 quarts of oil in 100 miles and I also noticed that I was reaching temperatures of over 212*f. I also had smoke coming out the dipstick tube when I checked it out. So I went to the secondary roads and ran 40-45 MPH after topping off the oil. When I got back to the house, I checked the oil and found that I was down another 1 1/2 quarts. I did not notice any smoke coming out the dipstick tube, but it was dark. The engine also ran about 5-10* cooler on the way home after slowing down. I also noticed that over the last month, that the vacuum has dropped from 18" down to 16". I also detected a very slight miss at idle.

I see no smoke normally and I have no leaks. I have seen some smoke at the exhaust on heavy acceleration. I am going to check the sparkplug wires and see if that is where the very minor miss is at idle.

Now I can not remember how to check to see if the valve guide seals are bad. I am going to pull the sparkplugs later this week to read them, when I return from a business trip.

#2, I had someone tell me that there was a possibility that since this coach sat for quite a while, there is a possibility that the oil return holes in the heads could be blocked. This would cause the oil to sit around the valveguides and not be pulled back to the crankcase and allow the oil to get sucked past the seals.

This coach runs strong and solid while I was on the freeway. The vacuum gauge is also very steady unless I have to accelerate on an incline. When I decelerate, I am seeing over 20" of vacuum.

One other thing, when I pull the dipstick, one side reads 1/2 quart lower than the other after I have driven it. At oil change, I see a smaller difference in the readings. I can't believe that this engine only takes 5 quarts to fill up to the full mark with a filter change when I service the motor. Is there a part number to verify the oilpan so that I can make sure of the oil capacity? I might have the wrong dipstick?

"Doc"

 

I would run a compression check. If this thing sits a lot you could have a frozen piston ring which would cause both a miss, and oil consumption. also pull the valve covers if there is a lot of sludge then yes the oil return holes may be plugged.
You didn't say how old it is, but I would bet on the valve seals bieng bad, but this usually just causes oil smoke on start up, and little else (most SBC don't have any valve seals after the first year yet they don't burn that much oil because of it)

 

Opps, this is a 1990 460 EFI and it is in a motorhome.

I think that by SBC, you are referring to a Small Block Chevy. I have built many of them, and unless I use a mushroom style of seal, it uses an "O" ring style.

I know that the "O" ring just causes the oil to not run down the side of the valve stem. I have never been inside a 460 and I am not sure what style seal they are using.

OK, I guess I have to order up a set of
Valve cover gaskets
Sparkplugs
Sparkplug wires (went out tonight and the AM radio is terrible with spark ticking)

I think that I might also need a starter, as when I got it warm tonight, it really did not want to turn over. After I let it sit for a while and cool off, it turned right over. I checked the battery (new last month) just to be sure and it had a full charge.

Lots of work to be done in this coach during the next two weeks.

"Doc"