One header pipe HOT,,,others NOT...

[65Val]

OK, this isn't a Mopar problem, but the principle applies to Mopars as well.....

My son's off-brand(Ch*vy) small block develops one really hot header pipe right after start-up (250*+), whereas the other 7 are quite cool (~100*) at that time. We have backed off the exhaust rocker for that cylinder until it clacks good (thinking lifter pump-up) , but the problem still happens. I'm thinking that combustion gases are being pumped directly into the header because that exhaust valve not actually closing completely, or could we have a burnt valve?

Any input is appreciated....

 

[67Dart273]

That cylinder running lean?

 

[65Val]

That cylinder running lean?

Could be. The engine also has a distinct miss in it as well, probably from the lean cylinder?

We tried spraying carb cleaner around the intake manifold gaskets, and got no change in engine RPM or sound, so we didn't think that the problem was a vac. leak.

 

[Inertia]

which cylinder,, I'm guessing #5 or 8.. modulator hose???

 

[65Val]

which cylinder,, I'm guessing #5 or 8.. modulator hose???

It's #6...3rd one back on the pass.side. Mod.hose is hooked into the full-time port on the baseplate of the Holley carb.

He's got a wideband 02 sensor on that bank and it says the things' lean all the time, even though we've jetted the primaries up 2 or 3 sizes.