Compression coming back thru intake

[EO2NMCB]

Been using the TM-34, also did a search, but did not find much. When the truck was running it sounded like compression coming back thru the intake. Also alot of blue smoke out of the even cycls. Pulled the intake and vavle covers, all valves moving, push rod and rockers arm look good. When cranking with intake off, pink wire pulled, did not feel or hear compression coming back up? The rubber in the torsional damper looks good, did not look out of round when cranking. Any ideals before I have to pull the engine?

thanks all in advance.

 

[85-m1028]

not sure what you mean when you say "compression coming back through the intake" the intake is wide open and can sound very throaty or growly.

off the top off my head I'd say bad valve seals, posibly head gasket.
cracked head or pre cup..

you could pull the bad head and inspect it..

 

[dilvoy]

A compression test should tell you if you have any bad valves.

 

[dependable]

Compression test may also tell about head gasket.

 

[THEROAD]

Sounds like headgasket. She is leaking between two adjacent cylinders.

 

[EO2NMCB]

Update, ran a compression test this morring, #6 cyl about 50lbs lower than all others. Glow plow was oil fouled, all other GP's clean and normal. Went back to GP in # 6 after just cranking was fouled again. So bad head gasket or some thing in the head or does this sound like something in the lower end??

 

[underdog]

A compression test will do what you have done, locate a bad cylinder or cylinders. But does not do a very good job a diagnosing the problem.
A leak down test on the bad cylinder will show you the problem.
My 2 Cents = Do a leak down test on the problem cylinder.
http://www.carcraft.com/techarticles/116_0406_cylinder_leakdown_tester/index.html
http://www.vmaxoutlaw.com/tech/leakdown_tester.htm