Hello Tim,
Have had the cylinder off and it appears to be the correct one,but I can't see a number stamped on it. It has two bypass ports but they are parallel at the top, I believe the venom (?) has a stepped top to the ports. The exhaust port is the large single slot rather than the later dual slit type. The barrel and piston are in excellent condition with no sign of any scoring, even the normal pattern that you would see after light running. The copper plated top of the piston is shiny bright. There is a head gasket in place and looks good, the head and barrel were tight. So it all looks good, rightdown to the sub piston induction
The only problem that is apparent is a slack ball joint. I have had this problem with the later Estes assembled product engines that were being sold for $4.95 a year or two back, but never with a genuine Cox assembled engine. I realise that a slack ball joint points to the engine having been run, but in all honesty this does not appear to be the case here.
My hearing isn't that good, but I can maybe hear a slight leak when turning over by hand, but I can't be absolutely sure of this (old age has its problems!).
It all looks as though this is a "real" Black Widow and not one of the later Estes so called Black Widows. Maybe I just have a dud engine, I suppose it did happen with Cox, but fortunately this is the only case I have come across. I will check with some soap solution to see if the head glow seal is OK and also around the head gasket. If this doesn't show anything up then it must be a poor selection of piston and cylinder. I will try some spare pistons that I have around somewhere. Other than that I will try running it in and see if it does get better, but like you, I have my doubts!
Thanks,
Andrew.