I had this in another post but it wasnt the main question so it never really got answered. My 73 F100 302 that I have been messing with sometimes smells like its burning oil. Noticed at start up and when reved it. No oil at all on plugs though. Gas is rotten and needs to be treated, could be part of problem.


Every spark plug looks like this. Only thing I know is maybe valve seals bad. Engine is all original with 51,000 miles. All cylinders tested between 140-150psi.

 

Looks like normal to me so far, like they were put in recently.

But the pic isn't focused on the plug...

 

Plugs have been in since May. It has been driven quite a bit and has set and idled alot. It has set and idled 20-30minutes many times to burn out the old gas. Even when it idles that long if I take plugs out they are still white inside and caramel colored on the end. I would think oil would show up by now?

 

Then count your blessings, your rings are fine!

Poor rings foul plugs with oil in no time at all.

This is what you want to look for when you pull the plugs off, all clean with a tan deposit. This means it's been operating properly.

 

So more than likely Its a combination of bad gas and valve seals worn? The valve guides wouldnt be worn to the point of being out of spec with only 51,000 miles would they? Original owner was 90yrs old and confirmed its never been apart. Might help to add also that this is the most its been ran in the last twenty years. It sat in a barn. Original muffler also, so no telling what is collected in it.

 

Are you completely sure it's been burning oil? Perhaps you have an external leak, like a dried up gasket.

Worn/dried-up seals will give a snort of blue smoke on startup after sitting for a good portion of time (like overnight). Reposition the passenger side mirror till you can see the exhaust tip. Then start the cold engine while looking at the exhaust tip. That's the only time it will burn oil.

 

Well now that you said that. There is no oil on the ground and the dipstick is showing full(I havent added any oil either, since May). I can see it at start up or when I rev it up. Might just be smoke from the nasty old gas. Im not real good at distinguishing colors, it looks bluish/blackish to me. Maybe Ill get a friend to look at the smoke at start up next time to get a new set of eyes lookin at it.

 

That is exactly the reason... The guides might be OK, but the little rubber O-ring designed to keep the oil out of the cylinder, is leaking.

When you shut the engine off, the oil slides down the valve stem, and instead of into the head, down the passages and into the block, to be pumped again, it slides down the valve, sits on the valve head, when you start it up, the valve opens, and the oil goes into the cylinder. At high RPMS there is so much oil being pumped in the valve train, it also gets in...

The Plugs look fine... My opinion? Run it. Those plugs are to nice to dig into an old engine. It really wont hurt anything either.

 

A small puff of BLUE SMOKE at start up only means the valve seals are worn/dried-up. Not a big deal.

But when you say it puffs smoke when you rev it...which color is it?

BLACK, MISTY SMOKE = unburnt fuel, indicating too rich.

BLUE, THICK SMOKE = oil burning in engine.

WHITE, THICK SMOKE = coolant burning in engine.

Having a buddy look at it with is great. Two heads.

 

The smoke is pretty thick when I rev it. Smoke looks a little blue, mostly more of a grey. Spark plugs are spotless though, they are extremley clean. Inside of plug is still white and tip is caramel color.


Found out something else today that is adding to the problem, may be the problem. I need a new fuel pump, noticed the smell of gas in the oil.

 

Bad Fuel pump leaking gas into the oil, would do all those things you describe.

Fuel dilutes oil, and lets it pass through the seals and rings easier.

Don't drive it untill you change the fuel pump (If it's bad), and change the oil and filter, along with the new fuel pump. Then check back with us if it's fixed or not.

Good luck.

 

I havent got to changing the oil yet. It will be a few days before I have time to mess with it again. I did have time earlier to change the fuel pump so it is new.

I am thinking about using 15w40 Rotella for the upcoming oil change. Anybody see a problem with doing that?

 

No problem at all, it's a diesel rated oil, high zinc content, great oil, i've always used it in all my trucks, never had any issues with it.

 

Got the oil changed in the truck. I havent driven it much(had a belt brake in one of the back tires). The oil I drained out ran out almost like water. Now most of the smoke smells like the engine is getting to much fuel instead of oil. I noticed that I still have a vaccum leak(When I rev the engine up I can see smoke come out from around the egr plate area. Its probably just the gasket that I have used more than once so I will get another one. I think I have a crappy reman carb to so I am going to take it back and get another one just to see.