Missing on the 6,8 I have done everything. Please help

[datguysaL]

i believe u can test for the this. when i had the same problem with my truck, the misfire at 6 and 8, i was told to get piston 6 and 8 in compression stoke, thats where both intake and exhaust valves are closed, and to use a threaded fitting to put in place of the spark plug and supply air, only this is that i dont rmember how much air i was told to supply. the guy had told me to listen for air coming out the intake, exhaust and bubbles in the coolant.

i didnt have to do any of this becuz it just turned out being my carb being dirty.

somebody on the board might know what test im talkn about. maybe they can explain how it goes.

[Corts60]

If it turns out that the head gaskets are fine, the only other thing I can think of would be a flat cam. Do the noises you currently hear sound like valve train noise?

A quick way to see if that is the issue is to pull the valve cover, start the engine and look to see if the rockers on those two cylinders look like they are not lifting as much as the rest.

[billnorman]

I think your friend was right. He was checking the valves and pistons for seal and the head gaskets. I'd use shop air pressure because the piston pumps up to 200 pounds so 140-180 shouldn't hurt anything. Chevy doesn't use replaceable valve seats in their older motors or I'd think he had a loose one. He might check for loose valve guides if they have been installed by a machine shop. He may have some bent or flexing pushrods, or valve stems eating rocker arms. They will eat into the rockers specially if the valve geometry is bad. He says he's set the valves, so they must be solids. One must watch the valves, chevy will eat the lobes off of the cam if it wants to.

[billnorman]

I just read Fireball's previous entry. Aluminum heads. Then they DO have valve seat inserts. One could have come loose, it's not unheard of. Then your static compression will be fairly good, but when running it can rattle around. $ounds like it's gonna be expen$ive.