I’m at my wits end. Parked the '70 'vert with 351C a month ago and it was running like a top. Now it barely starts, idles like crap, and bogs so badly I can’t drive it. Here’s what I’ve tried:
New plugs, new Pertronix II module (I had a known good spare), new coil, plug wires, visual inspection of cap and rotor (neither more than 3k miles), checked fuel filter screen, removed and verified movement of both float needle valves. I replaced the vacuum line to the distributor because it had a junction in it that looked iffy. Can’t find any other vacuum leaks.
Carb is a 5 yr old Holley Street Warrior that has been absolutely rock solid and totally dialed in until I parked it a month ago.
Sometimes it will start and drop into a great idle. Sometimes it runs rough has hell and stalls repeatedly requiring starter fluid to get started. Then it idles fine again but feels like it’s missing when you goose the throttle.
Is there anyone in the DFW area that might be willing to take a look? I’d come to you but the can’t be driven. I’ve got all the tools including a timing light but I’ve never touched the distributor.
That certainly sounds frustrating…
Based on your list of checked and/or replaced items, I would suggest consideration of a carb rebuild. And, also checking the distributor vacuum advance to see if it is functioning properly.
Hope you are able to get the situation solved.
I know I probably sound like a broken record on here, but I fought that same thing for months on my 70 351C. My problem was scale and rust in the original fuel tank. Fuel filter was always ok when you blow through it, but the sediment was fine enough to get through it and plug the carb passages. Carb rebuild fixed it for a few months, and then it returned. Had to replace the entire fuel system to get it fixed.
I hate to see parts thrown at a problem. So many variables are now involved that it gets harder to troubleshoot. We all tend towards the similar issues that we have seen. However the best way to approach it is by testing.
Is it running incredibly rich? Black exhaust and even spitting water from the exhaust? Is it too lean? If you manually close the choke does it clean up? Is the gas more than three months old?
Thanks for all the good advice. I did notice something else - fuel spitting out of the front vent tube on the carb. I pulled the float needle valves again and they are worse than I thought. The front one especially was sticking. Those are cheap, so I’m going to replace them and re-adjust the floats. I’ll see how things go from there. It may be carb rebuild time. I’ve tried to run ethanol free as much as possible lately but that wasn’t an option the first 2-3 years this carb was on the car.
fuel these days is horrible I run Lucas in everything it helps a lot on all my stuff also octane booster is not a bad idea add a few extra filters that will help keep out rust if you see it but don’t just replace tank you can actually drain it and seal it in place I have done several may not be perfect but so far I have not gotten any more rust if you want to try contact me I will explain