After repairing a timing chain and doing a valve job on left head, the #4 plug gas fouls almost instantly upon startup, I have double checked timing of valves and ignition, swapped injectors, swapped wires, ran compression tests, even swapped pipes from injection dist from cyl 3 to 4. The trouble always returns to cylinder 4. I removed the intake manifold to see if there was an error in installation. Looks right and the gasket is well imprinted. Any ideas?

I'm not an expert, but it sounds like either you're getting no spark or air in Cyl #4. How many cylinders do you have? If you have 8, maybe you're running on 7 without knowing. Depending on your car, it may be possible to see whether the spark plugs work by putting the ground electrode on your engine head while someone cranks the ignition a few turns. If you are getting spark, then you're probably not getting any air.

Btw, by gas fouling, are you talking about wet, clear fuel? Or are are you talking about a form of carbon fouling--wet or dry black soot? If it's carbon fouling, then none of what I said above applies....

It would help a great deal, if you provide us with the year & model of your car.

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2007 C 230 Sport.

Check the cap and the plug connector/resistor at 4

ok, it is a 1985 380 se. V8. the cylinder in question is on the passenger side closest to the firewall. I did not mention new wires etc as that seemed the simple first step. there is indeed spark and even new plugs do not fire. when pulled out they reek of gas and are soaked in the stuff. The valves do indeed open and close. I do have a bit of experience with engines and it seems to me it should run. A bit of a puzzler.??

Different info..
Your first post indicated you are having a #4 problem on passenger side and you did the head on the left side?
Now, you say all the plugs on that side are fuel fouled or is it still just #4 ?

What did you have on your comp readings?