A slow death

[Fleetlover]

Have a problem with the 250 in my 71 that I can't seem to correct . bought the truck about a year ago and drove it some but not a lot . Always needed to be choked and accelerator pumped to start and would not run decent until warmed up . When warm it ran ok but no powerhouse . Also many times if accelerator was releasedquickly it would stall . I attributed this to worn carb . Over last month or so has gotten progressively worse . Will start but can't be driven. Acts like advance is not working . PO installed HEI . Mechanical weights are free and Vacuum canister looks good . Pulled three plugs randomly and all were perfect coloration . HAs new carb fuel pump cap rotor and ignition module . Yesterday while looking things over again and hoping for divime inspiration I noticed that three of the manifold bolts had not been fully tightened In fact one was barely in the head and thought it was stripped but replaced and got them all tight . Could I still have a vacuum leak from running like that which would be great enough to affect the vacuum advance ? Burnt valve crossed my mind but seems would still start and run but skip if that was case . Would sure like to take a drive . Any help would be greatly appreciated . Thanks George