exhaust popping

[jdl71]

They are all gapped at .035. They are a medium brownish color, they have very few miles on them. I also shut the doors, turned the lights off and ran the engine, did not see any arcing anywhere. I've pulled plug wires off one at a time while the engine was running and each time I could tell a definite difference so I believe they are all firing.

[TJ's Chevy]

Good to know, that means you can almost put ignition out of the picture. All wires are in proper order...plugs are firing and in the correct gap range. Valves are adjusted, but have not been tested for leakage? I would assume the valves are ok as it is not back firing through the carb...the only thing it is doing is popping out the exhaust. Does it spit and sputter when you stomp on the throttle? If so you can count on valves not seating or being to tight or a vacuum leak of some kind. I have an exhaust leak on my GMC's 305 V6 at the gasket between the flange and exhaust pipe. Still smooth as silk out the exhaust except you can here poofing under acceleration. I doubt an exhaust leak would cause that major amount of popping. If a cam has gone flat it can cause popping as well. My 292's cam went flat from what I could tell and it popped at idle and when you reved it. Before you do a compression check...fire the motor and let it get hot...then pull the dipstick. If a ton and a half of smoke and air comes out then you know you have problems with the rings. That's the way I've done it.

[jdl71]

It does not spit and sputter if you mean like it's going to lay down, it revs up fairly smoothly. There is still popping. Does not backfire through the carb. It does pop at idle, I can hear it while under load, and when decel it's considerable. I did a compression check on it last year and it seemed ok, but I did not try pressurizing the cylinders. Earlier this morning when I was fiddling with the valves I closed it up and ran into town, and I apparently left one too loose, so I ran through them again with the engine running until I found the one causing the clatter. After that it seems like the popping is worse, but I don't know I may just be imagining it also. I could tell that I was gaining and losing rpm while adjusting them though.

[TJ's Chevy]

Originally Posted by jdl71

It does not spit and sputter if you mean like it's going to lay down, it revs up fairly smoothly. There is still popping. Does not backfire through the carb. It does pop at idle, I can hear it while under load, and when decel it's considerable. I did a compression check on it last year and it seemed ok, but I did not try pressurizing the cylinders. Earlier this morning when I was fiddling with the valves I closed it up and ran into town, and I apparently left one too loose, so I ran through them again with the engine running until I found the one causing the clatter. After that it seems like the popping is worse, but I don't know I may just be imagining it also. I could tell that I was gaining and losing rpm while adjusting them though.

You might try adjusting then once more...this time with .006 clearance. I did this on my 292 and it had more power than ever. Reason being was because it had recessed valves. The popping was less and it pulled better. But shortly after I had the whole truck apart. You can adjust to clearance with the motor running and you'll be fine...if it makes no difference put them back where you're happy and move on.

[jdl71]

Ran a compression test.

1 120
2 180
3 180
4 180
5 175
6 165

Adding oil to #1 brought it to 135ish. So looks like valves and rings in that hole. I have another head from another 230 that was running well until the timing gears chipped a few teeth and started slipping. I took it off this afternoon and the valves "look" ok, not terribly carboned up but is there anyway I can tell if it has hardened seats? I assume I would have to get one of the valves open or pull one out and look for a ring around the seat?

[jdl71]

#1 pressurized to about 150psi, both valves closed (or at least should be) obvious slack in rockers:

https://www.youtube.com/watch?v=kefTrDiNG0w

My apologies for the poor videography

[TJ's Chevy]

Valves look to be the issue there!

[TopFuel1966]

Bingo!!

[jdl71]

Ok, so here is the head I just pulled off



This is the offending cylinder



I guess I was expecting something more obvious, like being able to see daylight under the valve or something, idk. Here is the spare head I have been filled with diesel for about 2 hrs now so far, no leaks



I'm sure this is not the most scientific method, but if I go out and check in the morning and the chambers are still full can I assume the valves are probably seating properly?

BTW the bottom end looks pretty good, next to no ridge on the cylinder walls.