[SailorJ]

Hello I'm new to the group and I need to pick your brains! I have a 1964 GMC 3/4 ton with the 305 V6. I have been refurbishing this truck since last summer and finally have it all back together with the exception of a few minor things. About a month or so ago, I was idling the truck in the driveway to try and get my lights going as I didn't want to do it on the battery alone since my battery was old and dying out. On about the 5th time idling the truck I heard the rpm getting slower like it was going to die so I gave it a bit of throttle and BAM! It back fired and died. I let it cool down thinking maybe I had overheated it and attempted to start it the next day. It started but was rough. I asked my dad what he thought it might be and he said maybe since the battery was no good that it didn't have enough juice for the coil to provide strong spark. So I bought a new battery. Problem was still there. Then I noticed two plug leads were swapped to the wrong cylinders so I fixed that. (Don't know how because I never messed with them.) Opened brand new distributor cap that I had replaced and adjusted rotor tang and cleaned all arc areas. Truck fires great! My parents came to visit about 2-3 weeks later and I wanted to start it up for my dad so he could see it run. Once I started it, it idled for a minute and then started knocking! That was surprising as it had never done that before! So my Dad and I proceeded to remove the oil pan to check internals as I thought it might be a rod. Boy that was a chore! I had to cut my exhaust crossover off just to slip the pan out! I couldn't see ANY problems in side the bottom half. Rods, crank, cylinders, pistons all looked fine from what I could see. I took the plate off of the bottom of the oil pump to check if internals were good and it looked fine as well. The oil pump is pretty stout so I couldn't imagine it breaking! I have run the motor with oil pan off also for a minute to possibly hear something but that was a no go. I waited for two days for the new gasket to come in and I installed the pan and poured in new oil. The knock is still there but it only seems to happen once the engine starts to warm up. I ran the motor with the valve covers off and everything is moving and is intact. I have run the motor while using a large screwdriver or metal broom handle as a stethoscope listening in all areas. NOTHING! Also, I have taken the dust cover off of the bottom of the tranny to check the flex plate and torque converter bolts as I was told they could come loose. I can't find anything!!! Please give me some pointers if you have any idea of what this could be! Thank you!