Still periodically trying to get the '55 GMC 503 started. Most things appear to be fine: good spark, decent compression, but possibly a fuel issue? I posted earlier about the unusual Holley 885-JJG carb with governor - rebuilt it following the manual (looked clean and correct, best I could tell). Fuel is getting to the carb as seen thru visible filter just before it. But no pop, backfire, dampness on plugs, nothing. Also no response to a few squirts of starting fluid. It's not a carb that you can look inside to see accelerator pump action; and I'm not sure, due to the unique design, if starting fluid has a direct path to manifold as in most carbs. I wonder if somehow the vacuum controlled butterfly is not open or opening correctly. The mechanical response when applying the gas pedal is directly to the accelerator pump but not directly connected to the butterflies. BUT I'm not 100% sure it's a fuel issue. Murphy has taught me that what seems like one thing may actually be something quite unrelated. Your ideas?
