I have a 72 Cheyenne with some smoking problems. Engine is a 402 with about 10,000 mi on the rebuild. The truck sat for about 5 years, but I recently have started to work on it. The passenger side exhaust is putting out blue smoke only after getting warmed up, not on start up. Compression is normal on that side. Maybe an oil ring stuck after so much time sitting? Or maybe a valve seat dried up? Any help would be appreciated

 

That'd be my guess.

 

Valve seals-but do both sides.

 

I was thinking valve seals, but it doesn't smoke at all upon start up. Blue smoke starts to appear after about 4-5 minutes or when engine is warmed up. Pulled plugs again today to check cylinders, all clean. I'm not sure where to go from here.

 

Your compression is good, I'd again think valve seals. Even though your not experiencing smoke when first started dosen't mean what I believe you're thinking that it should leak "cold", think of it just the opposite if thats what you are thinking. Used to be a fitting you could plug into the spark plug hole to pressurize the cylinder to remove the valve springs to replace the seals without pulling the heads.

 

You surely can replace the valve seals while the heads are on,but it is tons better to take them off and if needed replace the valve guides that once hot show as bad.Pull both heads and have them checked out by your local trusted machine shop.

 

before you get to carryed away have some one oull a percentage leak down test to see if it is the top end or the bottom end causing the smoking problem ,seal's can dry up but after five minute's running and starts smoking ,it kinda sound's like the bottom end ,rings not seated or stuck .

 

That is a very valid point.Tests could lead you to the right repair for the issue your having.Consider taking apart a engine to find a needed repair like bad valve guides and seals.You do that and it still does the same thing.Then you still chasing the problem and what is the repair.So in the end the guides and seals where needed,but the oil rings where the issue.

I think that you can test as much as you like,but in the end it all leads to disassemble and close inspection.So I suggest you test to a point of somewhat isolating the problem and then stop there to take it apart.

Good stuff Old Dog.

 

So what exactly is a percentage leak down test? Is that something I could do, or do I need to take it to a shop to diagnose.

 

it is what the name say's ,it tells you how much compression leak's past the ring's and the valve seat's .they use it a lot in drag racing to check the condition of the engine so they can plan the service needed to be done .
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