[david.skinner]

Thank you everyone - very much appreciated. I've run some more tests this afternoon. I've removed all 16 of the inlet manifold bolts and re-torqued them to 25 ftpounds after removing the spring washers that were under bolt heads. They measured a bit short to me - I checked each for bottoming out first. so I think the manifold is bolted down well. I then disconnected the front manifold vacuum port which drives the advance (?) on the distributor and plugged it to isolate the distributor as a source of the leak. I checked all the mounting bolts and carb section bolts and tightened most of them and was a bit surprised that they seemed to be looser than I had set them. Maybe a few heat cycles can loosen them? Then started the engine. At 850 still about 14" and stable although as the engine starts to die so does the vacuum. At 1100 stable from memory about 16" vacuum. Interestingly at 850 it would slowly die to almost no vacuum and then pick back up again from very low revs - never seen an engine do that. Flatheadmurre, I looked carefully at the throttle shaft when I reassembled it and there was some very small but still noticeable lateral play in the RHS of the shaft to housing fitting. I had assumed it ok but maybe not. Thanks again.

PS if I disconnected the (electric) fuel pump and cranked the engine for a while should I expect to get 19" of vacuum if I didn't have any leaks and had the main butterfly valves closed?