Captain Obvious

I agree with Patcon. I'd cap off everything you don't really need right now, including the brake booster and the transmission. And yes, I think a vacuum gauge could be helpful. You should be in the 17-20 inches of vacuum at idle. If you're at 10, there's a leak somewhere. I also think pics could be helpful.

Oh, and I'd be hard pressed to believe it's a malfunctioning check valve. If you're off the gas pedal when you're on the brakes (as you most likely are), the check valve won't really matter because the manifold vacuum is high (because you're off the gas pedal). Does the idle go up a little bit when you press the brakes sitting at idle? That's a typical sign of a torn diaphragm.

The reaction disk won't just fall out all by it's own. If this problem occurred all of a sudden, it's not the disk. A torn booster diaphragm will cause a hard pedal, and so will a malfunctioning poppet valve inside the booster. Either way, you're opening or replacing the booster.

Hahahaha!! It's true!!

Couple comments to hopefully help the process... So I don't know exactly how you are handling the choke lever, but the typical process is to give it a good pull, crank the motor, and then as soon as it starts, push the choke lever forward "some, but not all the way off". It's not unusual to need partial choke for several minutes to keep the engine running smooth when cold. If you're pushing the choke all the way off immediately as soon as the engine starts, you are probably moving too fast. Give it some time to warm up with partial choke before you try to get the engine to run with no choke at all. Engines don't like to run cold. and engines that have sit for decades are usually grumpy about being woke up from their sleep. It'll probably get better as you get more time running, but first bunch of minutes on an engine that hasn't run in a long time? Don't expect perfection. Next is there's no way you should need to be running five turns down on a stock motor. If you're thinking you need five turns down, there's something wrong somewhere. I'm hoping that it's as simple as you need to leave the choke on partially for five minutes, but if the engine is warm and you need five turns.... There's something wrong. And that "lifter" on the bottom of the carb does not make things richer on that carb, and in fact, it does the opposite. When you lift the piston like that, it completely disables the carb by making it super lean.

Haha!! Not sure. Who would I ask for confirmation? ☺️

Spot The Bot!! ☺️

In all seriousness, I alllllllmost flagged him earlier today before he even ever posted. I think there was about an hour between him joining the forum and his first post. I should have followed my gut and done it. Would have looked like a master bot—spotter. Bonus points for those who see what I did there. Hahaha!

The flat top fuel rail should be perfectly fine to use with round tops. It has a restrictor orifice in the return line just like the rail used with the round tops. Other than the relocation of the outlet nipples that lead to the carbs, they are interchangeable. The engine uses a small amount of fuel at idle. In fact, if the carbs are tuned properly, the engine should idle for about 30 seconds or so just consuming what is in the bowls. No fuel pump supplying fuel necessary. So you should be fine running off the bowls until the pump turns on. It'll run for a surprisingly long time. First thing I'd do is look for vacuum leaks. A hose you forgot to connect, or a nipple you forgot to block off? If no joy there and you're double dog sure you have no vacuum leaks, I'd drain the bowls (disconnect the tube on the bottom and let the fuel run into a cup) and then refill the carbs with known good fuel. You can easily do that by disconnecting the inlet fuel line and sticking a small funnel into the hose. Pour fresh fuel in from a little cup until the carbs won't take any more. At that point, your bowl levels should be good and you should have 30 seconds of fresh fuel. Maybe disconnect the fuel pump so it doesn't push any more questionable fuel back into the carbs.

Two-fer! LOL!!! @siteunseen

Time to play "Spot The Bot!" @siteunseen It's a two-fer. >> https://www.classiczcars.com/forums/topic/58853-if-its-good-enough-for-a-sema-car-then/#comment-680341 I'm totally winning this round! Hahahaha!!!

Excellent! Glad it's working. And I agree with the assessment that it was either the second ballast resistor or just a bad connection. And the schematic sketch you posted looks good. It's the same thing as suggested earlier with the inclusion of the tach (blue) wire connection. Glad that worked out as well!

Sorry, but I kinda lost sight of the moving target... Can you make up a fresh picture sketch schematic of how you have things connected right now? Make sure to show both sides of the stock original four pin (not three?) connector. And include wire colors on everything?

Excellent analogy. That's a great philosophical thought exercise. Wonder what the right answer is.........

Gotcha. In that case, try this. The tach won't work, but the car should run. If this works, we'll deal with the tach next.