72 340 - What Did We Miss

I'm guessing your manifold vacuum is very low.What is your idle vacuum and at what rpm?
> make sure the secondaries are closed, pinch off the booster hose, and make sure the PCV is working correctly and is plumbed to the base of the carb on the nipple provided for it.
I would suspect a vacuum leak. It may be sucking air from the crankcase. Put a vacuum/fuel-pump tester gauge on the dipstick, and disable the PCV, and seal the crankcase, then start her up. The engine should now immediately begin to build pressure, NOT VACUUM. Do not let the pressure exceed 4 psi, it could start blowing out seals or gaskets.Don't panic, it doesn't build pressure that fast unless you have really poor ring-seal. If it registers a vacuum, then your intake is sucking from the bottom of the intake ports.
>If it's not there, then
Do a Leakdown test. Your valves may not be closing, possibly because of too long pushrods. This would produce a very low manifold vacuum.
In the event of a large LD number,back off the rocker shafts and retest. You can do the LD test now with the pistons at the bottom, to make it easier on yourself. Still a large number; might require pulling the engine down for inspection.
>And yes it could be cam timing,as mentioned, but ....... You wouldda had to have really messed up. There is a quick test for this called checking split overlap, which should occur within a few degrees of TDC.
>If the engine runs and revs up, it almost doesn't matter where the D is installed. You can make it run in any of however many teeth the I-shaft has. The only issue you will run into is with where the Vcan ends up, and it's adjustability between hitting the firewall and hitting something else. And of course you have to re-clock the wires, and sometimes custom wires have to be shuffled around to fit again. I wouldn't spend a lot of time on that, if it runs and revs up.
>Pick-up polarity is another issue, but this is also not your problem. If your polarity is reversed, you can still set the base timing exactly as normal, and it will idle exactly as normal; it just won't take revs very well, and the timing light will show a highly unstable advance system , plus numerous random misfires and skipped strobes, it's crazy to see.