My new camshaft feels a good bit better than the old one around town, but the engine doesn't really want to go past 4200-4400 rpm or so now. It pulls strong up until that point, and it feels fairly consistent. It doesn't sputter or backfire or hit a wall, the power just kind of starts falling off and makes me have that "better shift now" feeling like when you start revving off the power band in a motorcycle or old car without a tachometer. It revs over 5000 sitting still in neutral no problem.

I started freaking on fuel pressure and replaced my slightly-kinked fuel hose and fuel filter before I started theorizin'.

The theory:

My loose old timing chain was letting the engine rev higher because it was pulling less air down due to delayed intake valve opening. My new chain and cam are "correct" yet worse because I'm actually hitting the airflow limit of my Carter BBD carburetor, which I can fix by installing the Performer and Carter AVS I have almost ready to go. My symptoms sound most the same as people reporting stuck secondaries on four barrels.

Reasoning:

The horsepower peak for my engine in 67 was listed at 4400 rpm. The biggest Carter BBD ever made was 325 cfm. The next step below that was 285 cfm.

Let's assume I have a 285 cfm since they also installed those carbs on 383s, and they'd probably use the biggest ones on the big blocks and save the smaller ones for 318s like mine.

If I use any one of the carb cfm calculators on the web (which all seem to estimate on the low side) and assume a terrible engine volumetric efficiency of 75%, they say I should need roughly 300-340 cfm with a max rpm of 4400. I.e., even though these are fudgy numbers, the stock engine and carb setup is peaking where it is because it's just about out of air to flow at that RPM.

Does this sound like a reasonable conclusion or am I talking out of my butt?

I just don't want to start chasing down nonexistent fuel or ignition advance gremlins if my "problem" can be fixed by adding on a carb with secondaries.