The auto transmission is playing up scince i have put a different manifold on my 1200.

The vaccume lines for the auto only plug into one side of the manifold (two cylinders) and I was thinking that now the vaccume is not strong enough to change the gears properly
Can I get a more sensative vaccume switch for the auto?

Or any sujestions?

It may be easier to plumb the signal to a second nipple on the other two cylinders, so it gets all four again.

You can get adjustable vacume modulators go to an auto specialist to get one dont go to auto parts shop they wont no much. You can also change the modulator pin length but make sure you no what you are doing if you do that

Thanks Ill see an auto place about it.

V-A-C-U-U-M,... Vacuum

The E49 Valiant chargers from the 70's didn't use power brake boosters. Why?... With triple Webbers, they just didn't develop any significant vacuum signal, so the booster was just extra weight to cary.
This engine used over 88 cubic inches of swept volume to draw air from one Webber while even an A15 uses only about 46 cubic inches.

The Datsuns auto trans was designed to work with the vacuum signal that is generated by a standard engine. If one fits dual Webbers [or similar] the vacuum signal is significantly reduced, throwing all the shift characteristics out the window, which is what is being experienced here. Hooking the signal from the other two cylinders into the line should help, but probably not by much. A hot cam will just about destroy any vacuum signal completely.

Talk to a savvy trans specialist & rebuild the box with stronger components where available, see if there is a fix for the vacuum modulator problem & this may mean a full manual over-ride, & use a higher stall torque covverter to allow the engine to devlop a little torque before you launch.

I suspect that about $1000 should go a long way towards making it all work.