I recently finished an almost two decade restoration process on my 67 with a 400 engine which involved replacing or rebuilding everything. The car was missing a lot when I got it. I replaced the 326 with a 400 and rebuilt that. It already had a TH400 so I rebuilt that. Bought a stock type intake and carb on ebay. Carb is a quadrajet off a 1969 428 Bonneville which I've rebuilt and think it's working pretty well. It idles well with like 19" vacuum and drives great. Stock type mechanical fuel pump. Engine runs well and I can spin the tires pretty easy which is fun.
The engine cranks fast and easy hot or cold so no issues there. I put in a high torque starter, 750 CCA battery, and 2awg cables which all together completely fixed up the slow/no-cranking-when-hot problem I had before.
My carb is one with a divorced choke coil in the intake manifold exhaust crossover which you can see in the attached pic. Accelerator pump works. Choke works. Generally the carb is all good I believe. It idles at like 900 in Park fully warmed up which drops to maybe 750rpm in gear while holding the brakes.
This is the only carbureted car I've ever owned so I have very little experience. To start I'll give the accelerator pedal a press or two to the floor then release and crank the engine with foot off the accelerator pedal. When cold it fires right up immediately to like 1500 rpm high idle. Sounds robust, engine speed flare up when it fires off is great.
My issue is actually when the engine is hot. I do the same procedure pump the accel pedal once or twice then crank with my foot off the pedal. As I said the starter spins the engine over very well so no problem there with cranking speed. It will light off right away but engine speed only rises for a second to like a few hundred rpm then it falls back down to cranking and will start after a few seconds of cranking. When it does start it's like a very weak start that does not flare up at all. The engine sort of sputters up to idle speed but it is not a robust start. You know on a new car whenever you start it the engine will flare up over like 1000rpm then fall back down to the idle speed, that flare up is really what I'm missing here but I don't know what is normal operationally or behaviorally for an old car like this.
My question is what do you all do with the accelerator pedal when starting cold and hot? Should I expect a robust engine start when hot with the engine speed flaring up to say 1000rpm before falling down? Am I supposed to be holding down the pedal halfway when hot or something to make up for the high idle speed cam not engaging when it's hot?
