Right cylinder bank runs super lean on 2.0l Type IV /PDSIT carbs

[DrElch]

Hi folks,

I've been facing a series of issues with my 2.0l stock CU engine. It was refitted and I've made 5000km on it so far.
It ran quite well. Had plenty of oil pressure, oil temp always fine and my afr gauge told me everything to be fine around 14.

But then all of a sudden things turned really bad. I heard a loud noise like a clicking valve (I've got hydros) and the engine started to run really bad with low power, very rough and with one cylinder less.
Mind you that the engine wasn't running super hot or anything.

Also my afr gauge started to be all over the place. The clicking valve noise vanished very quickly and I was able to drive it home.

I did some analyzing and I've found the following: afr gauge tells me, the engine is way too lean. Gauge goes beyond 18. one cylinder is so lean, that if you pull the spark cable from it, the engine keeps running at the same revs. Pulling the cable from the other cylinders causes lower readings.
Also I wasn't able to affect the idle speed a lot with the central idle circuit of the pdsit carbs. This didn't do much

Since then I've tried all sorts of stuff:

- Replaced all spark plugs, cables, cap, finger
- Rebuilt carbs
- replaced gaskets beween carbs and manifold
- tightened all screws
- checked for air leaks several time, but couldn't find anything. I've checked manifold, carbs, central idle connections
- checked for exhaust manifold leaks
- compression test 8-9 bars on all cylinders
- pressure leakage test on the cylinder in question: around 20% loss, which is still within the tolerance
- and last but not least: vacuum test. This test told me a lot about my engine. Instead of explaining it, let a video do the talking.

I'm really running out of ideas.
My next step would be to remove the cylinder head. Anybody got a few cents to add?

[GARRICK.CLARK]

did you put a carb rebuild kit on the carb. Like replace all the gaskets and o rings on the carb. I did this to a set of pdsit carbs and the gasket between the carb body and the butterfly body was missing a pressed hole in the new gasket . This missing hole in the gasket was a fuel hole. No hole in gasket equaled no fuel to 1 and 2 cylinder.

[Fiatdude]

One quick way would be to switch sides with the carbs and see if your troubles switch sides too.....

If not, then I would put a dial indicator on the valves on the 'bad' side and measure lift as you turn the engine thru 2 revolutions -- the intakes valves should have the same reading and exhaust valves should be equal, the intake and the exhaust might not be the same, you'd have to check your cam spec's ..... Since the leak down and the compression are all about the same, and if the carb switch doesn't point to something, I'm guessing that one of you lifters has failed and this would show up in the above test as one of the valves is not opening very much.... drain your oil and check for lifter chunks too....

[Piledriver]

An issue like that that fixes itself can also be a loose seat that popped back in.

Another issue is if the "ball" type swivel feet are installed, the balls have been known to come off the flats under certain circumstances, and remove all lash, then fix themselves.

Swivel feet are incompatible with hydraulic lifters, tho, they will die quickly due to lack of lash not allowing oiling.