On my '56 gmc 270 six,I'm trying to figure out why it is running rough, popping and hesitating on acceleration, and seeming to have less power. I checked the compression when I got access to an assistant, and the readings were #1- 153, #2- 74/72, #3 155, #4 152, #5 158, and #6 155. Something is up with cylinder #2. Vacuum running was 20" with a steady 1/2" pulse. As noted in another thread, I recently blew up the muffler with an overly rich idle, and that is when this rough running started. I set the timing with the vacuum advance connected, and I think I need to try timing it with the advance disconnected and vacuum plugged, as common wisdom seems to be to disconnect it while setting timing. Also, when timing, the ball was below the pointer, and when I moved the distributor to line the ball up with the pointer, the engine would almost die. So I left it below the pointer, still visible in the flywheel window. It still often almost dies when you hit the gas, but not always. The #2 plug had fluffy black deposits. The heat riser was stuck on, now I got it stuck off. I replaced the coil and condenser, (points are new) and replaced the ballast to coil and coil to distributor wires, which seemed funky. It runs a little smoother now. I'm particularly interested in the next steps to figure out what is up with Cylinder #2, and then I should know if driving it will damage things, and how to fix it. It seems I should pull the valve cover and watch what happens, but I am not sure what to look for, and whether to look while cranking or running. I also would like to know what those compression readings mean in terms of performance- for example if I get the carb and timing right, should it be driveable?
Last edited by Dave Douglas 56; 07/26/2011 11:52 PM. Reason: added question
