[oak29]

I'm helping a friend with his A. We've had to replace the head gasket - it was blown - recon the distributor (cam and bearings shot) and rebuild the carb (jets missing from original!). It's running loads better but there's an underlying misfire and she's slow in pulling under load. We've timed the engine with a timing gun against one of those graduated scales bolted to the block, and it staying solid and the adv/retard lever is working fine. We've replaced plugs, dist cap and rotor with known working parts to eliminate any shorts on the electrics. We've done a compression test and all 4 pots are fine at c65 with a variance of 2 between them.
We've put a vacuum guage on and the readings, like freak's above, are flickering between 17 and 23. When you open the throttle and hold it at higher revs, it drops and stays between 10 and 17. When you read the diagnostic charts for what the readouts mean, it says a flickering reading like this indicates worn valve guides or head gasket issues. Two questions. 1.if you had a head gasket issue, wouldn't it show up in the compression test? 2. is the flickering needle perhaps a 'feature' of a cheaper guage? 3. I've been been reading about leak down tests. Could you use a pressure limited (say to 70) compressor to pressurise each cylinder (at TDC) to do the leak test; if not else what could you use? (a tyre pump?).
We're working on the car again tomorrow so any quick advice - particularly on Q3 - would be welcome. Thanks John