305 missing

Have a problem that I can't quite figure out. This is the 2nd time it's happened. Started my 305 up this afternoon as I was going to take it for a last spin before it's put away for the winter. It started up ok and I let it warm up and then had to shut it down to help my wife. Came back about 2 hrs. later and started it up and it was missing on # 3 & 7 cylinders, the same as last year and I had to replace those plugs. Pulled the plugs and they were wet with gas. Put new ones in and they worked fine. Now these excel shorty plugs have only 1,000 miles on them and except for # 3 & 7, the others have 5,000 miles on them and there OK. The plugs were black and as I said before soaked with gas. What would make these plugs go bad. One thing I do have a problem with is it's very hard to start as the carb looses gas in its bowl overnight. Really have to pump gas pedal to start it especially after sitting for a week. Any comments??

man that sounds real familiar.....before i ripped mine completely apart I had the nearly exact same symptoms as you are experiencing....dejavu or what......It was a mystery that I could not solve, My carb was getting fuel, but I noticed that my spark was weak, and sometimes non existant.....the only conclusion that made sense was the coil had crapped out at the end but from sitting for a while the wires looked corroded at the plug ends and maybe the wires were also shot, I just turfed them. I ended up in the end to just completely rip into the motor and make it race ready....I never did resolve that issue, but your problem is the same as I was having......if you are running the hei, might be the coil and or the wires. When I park mine for the winter I noe remove the wires and the cap and rotor and put it in the house to keep the moisture away from it......When you find the culprit please let us know...thanks

Took my Hei off and ran MSD with coil. Always had a good spark with both HEI and MSD. Spark tester show good spark so I don't think thats the problem.

i have a 1998 chevy cavalier with twin cams and i have a bad miss from the exhaust and is backfiring when you turn the heat on what does this sound like to you?

if you are runing a holley and the power valve is out .it will dump the fuel down the intake but will run bad may be float

I read of a problem similar to this. If I remember right, that person was running a carb much to big for his motor. The idle circuits discharge ports were making 2 of his cylinders run really rich. Hope this helps.

I had a similar problem! I have MSD HEI upgrade kit, brand new plugs and wires, etc. I started the 85 C10 up (it has a 305 too) and moved it in the driveway. It ran fine. I cut it out, pulled the 66 out and then went to put the 85 back about 10 minutes later. I start it and sounds like water in the cap and not firing right or cylinders were out. Well I didn't check the plugs but a guy told me to. Instead I just started it, it idled like it was way off timing and didn't idle too long. I started it again and help the gas and let it sit reving for about 3 minutes to clear it out. Left to help a guy build a 302 and probably 5 hours later came home and it started fine. No problems anymore. The guy I bought it from says it fouls plugs....