I just rebuilt my 502 and cant figure out why all my plugs on one side are very rich (2,4,6,8) and the plugs on the other side are everything else but rich. #1 looks lean, #3 looks normal, #5 looks like its really black, #7 looks normal but rusty. (no evidence of water other then the rust) plus when I look thru the spark plug hole in #7 I see droplets on top of piston. could that be gas or would that be water? Im going to go run it it again with new plugs Instead of Champions I'm going to try AC Delco.

What exhaust system do you have? Could it be an internal leak just into #7? I had that trouble with my Gils. It was repairable.

Other than that, it sounds like very uneven fuel distribtion. What carb and intake do you ahve?

Exhaust is Revolution Marine, stock manifold with stock weber carb. It a 1992 502 Mag. everything stock except for exhaust and a mild cam 139721 crane cam. Should of gone bigger on cam also changed over to roller. I just rebuilt the carb. What could cause uneven fuel?

How do you like the Revolution exhaust? Did you install prior to engine mods? If so, any performance difference? I hear some say yes, others say no, looking for first hand experiences....

Thanks and good luck!

Unfortunately I installed at the time of rebuild, so I cant really tell you. Sounds better. Could even be louder to tell you the truth.

heres a great lin for reading plugs, caveman gave it to me. spak plug reading 101 good luck

As you know mixture robbing takes places amongst cylinders. Some intake manifolds or ecm calibrations compensate for this well.

That is why you are seeing mixed results from cylinder to cylinder.

I would suspect that your problem is a leaking intake manifold. If the gasket is not quite right on the side thats running lean it could suck air. Also the water in cylinder could be from coolant/raw water from crossover in manifold.

Make sure that if you are running it on the trailer that you have the tongue high. Could be just flowing back.

and get those Champion plugs out of there, from my experience those are the worst plugs made. Go with either Ac/delco or Auto lites, Auto lite makes a great racing plug that uses a stainless end that I like for one it doesn't rust up in a marine environment. Not saying that is your problem but could be later. Champion's are known to blow the porcelain out of the head of the plug leaving that cylinder open and sounds like a blown engine. I have even had this happen with the only set of Champions I ever bought. I know quite a few people that have had the same issue with Champions so it isn't a one time thing.