97 4.0 starting to puff some blue smoke after just moving off. I've replaced the pass head over time but still on the original drivers head. Has anyone changed the stem seals using compressed air with engine in the van drivers side only

 

I have no idea how you would be able to put new valve stem seals in without removing the heads., especially sense you have NO overhead room to work on those.

 

The trick is to install an air adapter in the spark plug hole and pressurize it to keep the springs from falling in. But you're right; you'd be hard pressed to get any valve spring compressors to fit in the engine compartment.

 

Faster and easier to pull the head. Also gives an opportunity to examine valves, valve seats and heads for any cracks and measure valve stems/valve guides for wear.
With the head off, good time to pull and examine roller lifters for wear or damage.

 

I meant to keep the valves from falling in...

Yes, better to pull the heads for a thorough examination of all related parts.