I went out and drove my truck today. When I started it up, i noticed it was missing. So I figured that maybe if i blew it out, it would help. I tried to blow it out and didnt work. So i started taking spark plugs out and cleaning them. #3 was extremely wet and fouled out. The rest of them were perfect. I put a new spark plug in and it stopped missing. It runs perfect now, except now there is blue smoke coming out of the exhaust pipe on that side. does anyone know what the problem is?

 

You have a bad cylinder.
To find out exactly what the problem is, you will have to run some diagnostics and, or, take it apart.

 

id start with a compression test.

 

If you do a compression test be sure to remove ALL the spark plugs. Now, if you are seeing "blue smoke" then you are seeing oil being burned. Oil pretty much has to pass the piston rings to enter the combustion chamber. It is possible for oil to pass by valve seals but that causes start up smoke that soon diminishes.

You seem to have this narrowed down to a particular cylinder so I really see no need for a compression check. You replaced the fowled plug and the engine runs normally. Now you have an oil burning problem. Hmmmm.. I wonder what caused the initial skip in the first place? If by "blowing it out" you mean romping it down the highway wide open (or even close to it) then you must erase the belief that this will help anything from your mind. That idea could be why you are seeing the smoke.

A cylinder that has a dead skip is filling with unburned fuel. That fuel can strip the cylinder walls of lubrication. The rest speaks for its self.

Letting an engine do what it was meant to do (work) or "blowing it out" is an ok idea for a properly funtioning engine. It will not fix anything. It is just exercise for the engine. I hope my theory is not true as far as what may have happened to your engine. I would do an oil change and run it easy for a while and see if the smoking persists. Reason for the oil change is A. I dont know how long it has been. B. The "blowing out" fuel may have thinned your oil, however if this were the WHOLE problem the smoke would come out both sides. Just dont want to do any more damage.

Hope some of this is of use to you...

 

Most of these old trucks have been well abused before we get them. I know because I was guilty of not changing oil, powerbraking, overloading, overtowing , bat turns ,etc most of the vehicles I owned. I used to love jumping the RR tracks in our small town. Those trucks can get some air let me tell you. Out of all the POS vehicles I have owned since my teen years the FORD truck has lasted me the longest. I had a 78 f150 that was once underwater. I drained everything and cleaned it up it run great for a while. I forgot to drain the water out of the axle and it froze cracking the housing! I junked it like a dummy but that was one tough truck. The 71 I am fixing up will be my last. I don't like the new bodies.

 

well assuming this is a fe enigne i would pull the valve cover and look for missing valve stem seals they will break off and plug the oil return holes which builds up oil which is then sucked in the cylinder. also the intake gaskets start to leak sometimes.

 

I would have to agree with 390gashog. I have repaired a few 360s that done this. Those intakes and stem seals are troublesome. I had to pull the pan on a neglected 352 engine and remove "sludge" inside the pan and under the v/c. This stuff will keep circulating around inside the engine usually ending up in the return holes.

 

I have a built 302. It only has 5000 miles on it. The exhaust has quit smoking, it was the carburetor. I had too much fuel and not enough air. Thanks yall.

 

And by the way, oil bypassing valve seals does not soon diminish after starting. My truck didn't have a valve seal. All had disintegrated and my truck failed emissions cause of visible smoke.