cylinders 5 and 6 not firing
 

new rebuild on 2.4 w/zeinth carbs. I was running the car in 2 nd gear @5k rpms when it started to not fire on 5 & 6. leakdown for both cylinders cold is 0%. I got spark and fuel. I know i did not overrev the engine. and it happened suddenly. what could it be other than a bent valve.

When you say 0% leakdown, do you mean it's holding 100%, or it's losing 100%?

If they are holding full pressure, then it would have to be fouled plugs.

Or flooding float bowl, since those two cylinders share a common float chamber. If the stuck, or the needle and seat aren't sealing, it would flood those two cylinders and fuel foul the plugs.

I've never seen "0" leakage before. Are you sure?

It turns out that their was debris in the jets to those cylinders. It now fires on all pistons but running rough. slight miss thorugh out the rpm range. It miss's less when I get on the throttle hard.