Misfire and rough idle 327 small block

[mrdave03]

Hi All, I'm looking for more pointers on this mystery issue. The other night I was driving my 65 c10 with a 327 small block with Rochester 4bbl carb and after a short drive.. a mile or two..upon accelerating and lifting off the gas to slow down.. the truck coasted at idle a moment then upon accelerating again it began to smoke and miss terribly. I parked it at a cruise night and a buddy hopped in fired it up and it seemed a tad rough but pretty much ok. Checked the choke it was open as it should be. We adjusted the carb and it seemed fine. later that eve I went to head home and the truck was stuck at a high idle and within a minute began misfiring and smoking badly again. I limped it home. Parked it as it filled the garage with the smell of rich exhaust. Yesterday I started it and it seems to run fine again I drove it a few miles no issues other than it idles a bit rougher and has a tiny bit of greyish rich fuel smelling smoke. I checked the dwell it was 40 I set it to 30. I dropped the timing from 12 to 10 BDTC. I readjusted the idle to 500rpm and adjusted both carb valves till it hit the sweet spot on both. It accelerates fine and seems good other than it now sputters more at idle. I'm still confused as to what the mystery issue was two nights ago. Could it be a failing coil or any other ideas? I'll pull the plugs today see how they look. I'm going to check the electrical from the coil for any possible shorts. Also going to spray the vac lines with carb cleaner looking for a leak. Any thoughts are welcome. If I come across anything else today I'll post back.

[joedoh]

if you snapped the throttle shut on your acceleration run, you probably pulled some trash through the carb. I dont know exactly how you were driving, but if you lift off the throttle quickly the throttle plates close, the engine vacuum is still really high, and the engine tries to pull air from anywhere it can, raising the chance of dislodging some long hidden gunk.

I had a little 4 cylinder with a weber that I trusted but shouldnt have, after a fast run up the onramp I snapped off teh throttle and coasted a bit and found I only had secondaries after that. Webers are really easy to take apart, so with a butter knife on the side of the road I pulled the carb top and found an ancient fly wing clogging the main jet.

[mrdave03]

I'll see if I can see anything carb wise. I was driving normally other than upon making a right hand turn I squeezed the pedal just cuz it sounds nice and then realized I was in a 25mph zone and lifted quickly but had only hit 25 by the time I did.. but you may have a point. I pulled all the plugs. The number 7 plug was only gapped at 0.10 so reset it to .035. There was a tiny bit of oil on all the plug threads but that could be from oil on the block although the motor is a complete rebuild along with the carb last summer.. maybe 1000 miles ago.

[vgnope]

it sounds like a little trip down "take it all apart, then put it back together" lane.. maybe u did clogg a metering jet w som carbon debres..but if it is a recent rebuild, that shouldn't be the problem..junk from fuel tank??filter would catch it..
I myself am running into it aswell.. truck turns over, but no spark.. tested all elc connections,hei components..spent bout 4 hrs doin so.. everything checked out ok..put it back together,, fired right up...