HELP w/ 340+6 T/A Engine dropping a cylinder under load

[jimynick]

Does your dyno guy run EGT sensors in each header pipe? Shouldn't the A/F readings have been giving a clue as well? BSFC/VE too? Just curious. What led you to the conclusion? 

[Cuda Cody]

Yes, each exhaust pipe has a sensor.  That's how we knew one of the cylinders went dead under load.  Watch the first video on page one and you'll seethe temps drop in cylinder #8 from 1200 to 1400 down to under 700 in a few seconds.  It doesn't lean out, it just shut off and went cold dead / no fire at all.  We were ready to tear the engine open and go through it. Put in all new lifters and make sure everything was working. But we moved the front carb to the rear and the rear carb to the front. The dead cylinder (under load) followed the carb. That's when we knew we were close and starting looking in the carb. 

When the car was on the Chassis Dyno I could not see what was happening with each cylinder and only knew it was super lean under load.  That's why I built the 2nd engine when I did.  It gave me a chance to test all the components (distributor, carbs, wires, and stuff) on an Engine Dyno.

Does your dyno guy run EGT sensors in each header pipe? Shouldn't the A/F readings have been giving a clue as well? BSFC/VE too? Just curious. What led you to the conclusion? 

[61K T/A]

Which lifter type did you use?

We're thinking it might be a bad lifter?     They are new Johnson lifters.  If I replace the lifters in the 8 cylinder do I need to replace the cam?  I can use new lifters and it should be fine, right?  @Chryco Psycho

[Chryco Psycho]

new lifters on a used cam is no issue , once the am is broken in the risk is gone but you still need to use proper oil for flat tappet cams or the cam can get eaten up

[Cuda Cody]

I would have to look at the box for the exact number (I think it was 2011), but yes they are flat tappet.  Glad it wasn't the issue and it was only the carbs.

Which lifter type did you use?

We're thinking it might be a bad lifter?     They are new Johnson lifters.  If I replace the lifters in the 8 cylinder do I need to replace the cam?  I can use new lifters and it should be fine, right?  @Chryco Psycho

[Chryco Psycho]

I agree the carb is a lot more servicable