Vacuum trouble?

[johngmm7]

Having very rough idling on my 65 deville.  Plugs are new, HT leads new(ISH), carb rebuilt, new distributor cap and everything else I was able to think of is new and set properly but the idle is terrible.  It's worse when put in drive or reverse and sometimes engine cuts out.  I am now considering trouble with the vac system as a last resort.  Being somewhat of a dummy on where to start, I thought I'd replace every hose/tube or whatever as I don't fancy being charged an arm and a leg for diagnoses. Sensible??  Are there any complete vac kits on the market so I can just simply exchange old for new and save any aggro.

[savemy67]

Hello John,

Before researching/replacing vacuum hoses etc., perhaps you could disconnect the hoses from, and block off, the sources of vacuum for all vacuum actuated systems - at the intake manifold and carburetor.  See how this affects idle and off-idle performance.  While at this diagnostic step, you might want to check the distributor mechanical advance if you have a timing light.

If idle improves, a vacuum leak somewhere is a likely culprit.  If no improvement is noted, a mis-adjusted carburetor might be your next area of diagnosis.

Respectfully submitted,
Christopher Winter

[fishnjim]

Put a vacuum gauge in line before you get too far ahead of yourself, suspecting it's a vacuum issue.   
The other reply is on track.
If too much air leaks in it'll kill the fuel mixture and die out.   If the carb has a vacuum port, plug it off, and see if it idles out.   It could still be leaking air, if the rebuild wasn't proper.   (always keep a spare carb that is in working order for swopping out.)
Is there any other vacuum system problems, like with the "power" brakes?   
It'll run/idle without the vacuum advance, but it could leak air in if diaphragm is shot.  That's a small tubing usually, so not as suspect.
I'm pretty sure by '67 there was no pump just manifold. 
Make sure the timing is checked at the proper rpm and with the vacuum advance plugged off.   A golf tee was a tool box staple in '67.   It'd be hard to get right if it won't idle.   Check the points with dwell meter.   
Worst case; Depending on how many miles it could be blowby and that won't get fixed with tubing.   But should have had the same problem before you worked on it.
Trouble shoot 101: Always suspect something that's been recently changed, if it was OK before the work was done.   eg, all the plugs firing, etc.   Everything installed correctly and tight.   Recheck all the adjustment screws.