Hey /r/cartalk,

Came here a while back getting advice on getting my 1976 Malibu past emissions- ended up having it tinkered with by a mechanic specializing in restorations (he replaced the jets in the carb), and it passed. I was able to get it from Denver, CO down to Tuscaloosa, AL with nary a problem. I'm just a 4 hour jaunt from my final destination, staying with friends for a couple days before I start a new job, and I ran into an issue while driving around town today.

Basically, the car will accelerate up to 35ish and then stop accelerating. If I push on the gas, it slows the car down at this point. Idle is VERY high in neutral/park, and VERY low in drive. At first I thought I'd lost a gear or something, but when I asked my Uncle Doug about it (he's the car guy in my family), he told me he thought it was probably something wrong with the accelerator pump in the carburetor (the logic being that enough idle fuel was getting in to get it up to 35, but that when I pushed the accelerator to let in more gas, it was increasing the air in the system without opening up the holes in the bowl, causing it to drag) and gave me some steps to open it up and get at the part in question.

My question is, what am I looking for? I have a pretty ok idea of where the part's located and what is wrong, but I don't know what particular failure in that part is causing my problem (i.e. should I be looking for some pins that have come loose off of the arm, a broken arm, etc.).

Here is a picture of the carb in question (a Speed Demon of some sort), and this is a picture of the interior of the front bowl (where the accelerator pump linkage is attached). I've marked the part of the arm that hits the float in green.

If it makes any difference, I'd started it up and revved it a couple times to show off about an hour or two (I then turned it off and went to eat, caught a ride with a friend) before I ran across the issue. It made a slight high-pitched noise at the peak of the rev- only thing I can think of that's happened in the past 24 hours that was different than before.

A couple other question-y bits:

1) I like the idea of having a hot-rod carburetor in my car, but in practice, it's been a bundle of trouble. Will changing to a stock carb make things less stressful? (I found out the engine is a small-block 400 from a '75 Chevy Cheville if that helps with suggestions)

2) Will going to a stock carb significantly impact my performance? I'm not a street-racer, so I don't mind too much, but I still want the power of the 400.

Anyway, thanks in advance- I really appreciate the help.

Best,

-/u/Daveaham_Lincoln