so my 86 f150 (300ci) is burning a lot of oil. I think its the valve stem seals but I'm not sure. the pcv system is good. it leaks a little bit of oil nothing to bad. I hope it don't need piston rings. what do yall think?

 

I think you are asking people who don't have enough info to give a reasonable answer. But the classic signs of valve stem seal leaks is a puff of smoke when you start up, and smoking when you let off the gas, like when going down a long hill. In startup the smoke comes from burning oil that ran into the cylinders with engine off. In coasting it comes from very high vacuum in the cylinders sucking oil past the guides and seals. So, is that when your engine smokes?

 

You must be referring to an intake or exhaust valve seal?

Valve stems are these:

 

the engine smokes when I start it and when I give it gas. the smoke is a blueish gray color. it doesn't seem to smoke when I drive it but then again I really don't pay attention to it

 

okay so my dad said when he drove it it smoked when he let of the gas

 

Those are classic signs of the seals and/or the guides to be bad. But, before spending money on the seals you need to ascertain the overall condition of the engine as it may not be worth spending money on the seals.

 

whats the valve guide?

 

I know what the valve stem seals are

 

Here's a link to an overview of internal combustion engines. Page 16 has a cutaway drawing and Item D is the valve guide, which is the relatively soft piece that is pressed into the head and which "guides" the valve to center up in the seat. These wear and allow the valves to rock as they close and that frequently prevents the valve from seating correctly in the head. That allows leakage and that then allows the valve to burn if it is an exhaust valve. In addition, the rocking causes excessive wear in the seals.

So, just replacing the seals might be short-lived if the guides are bad. And bad guides can lead to burned valves. But, frequently the rest of the engine is well worn when the guides go. So, don't fix one thing without finding out the condition of everything as it can easily be a fruitless exercise.