Need help to set idle

[david.skinner]

More info and I feel like Alice going down the rabbit hole....

Changed the distributor, coil, and checked the plugs - bit dirty but I think ok so I'm going to rule out electrical.

When I rev the engine up and then release the throttle I get just over 20" of vacuum while the engine is slowing up. Once it reaches idle the vacuum drops to between 14" and 16" depending on what idle revs I've set. Does the fact that it will hold 20" for a few seconds mean that its less likely to be a leak?

2nd gotcha and this one might make you laugh (or cry). I disconnected the vacuum feed to the distributor and plugged in my gauge there and guess what - no vacuum at all. I think the feed has been drilled in the wrong place in the manifold and has never worked. You can see the vacuum port for my gauge in the base of the generator mount immediately in front of the oil filler in Picture 1.

Long shot from my limited experience but could the inability to set idle relate to the fact that the distributor has no vacuum at idle?.

Picture 2 shows the two existing vacuum ports on the manifold under the rear of the carburettor. They are two different sizes. Perhaps I could use the smaller one as the feed to the distributor?

I have many photos of the carb in pieces and as I reassembled it in case this was useful. I did notice a slight difference between the two idle tube (jets?) in that the top hole was in line with the screwdriver slot on one and perpendicular on the other. Couldn't see any difference otherwise (pic 3).

I had thought that perhaps needing to idle the engine so high that the idle mixtures would not be active but in fact I can easily get a stumble on both sides so its clear that they are having some effect. Over to you... Thanks