That is a great street cam/ hugely better than the stocker choices. Makes a ton of low-rpm torque, and and a modest amount of midrange. With decent cylinder pressure she needs no stall change and almost any 3.00 series gears.
And it will idle down to 550 in gear pulling itself on hard level flat ground. Maybe even 500.
Ok
my first thought is that the engine is getting air somewhere, not authorized by the throttle valves.
Here are your usual suspects, in most likely order;
accidentally cracked or stuck-open secondaries; see note-1
an un-capped vacuum port on the carb.
intake to head connection including in the valley under the intake
the carb base gasket(s)
a faulty PCV
any vacuum device running off the intake
a perforated diaphragm or broken control valve in the Brake booster
faulty guides
faulty exhaust valves
a hole in the plenum
see also note-2
--------------------
Note-1
here is your basic tune;
>Step one, disable your Ignition system by disconnecting the ballast resistor.
>Take the carb off the engine ,empty it, flip it upside down keeping the throttle closed. For this test, keep the throttle against the curb-idle speed screw, to prevent choke engagement.
> Identify your Transfer slots. They are the only slots at the front edge of the primary throttle blades. Reset your speed screw to make the slots appear to be about dead square, both the same.
> go to the secondary side and make sure that both butterflies are fully closed but not sticking. You may have to bend the link-rod to get this, and/or adjust the cracking-screw, and/or, if a Holley VS you may have to fuss with the secondary vacuum pod. Actually if you have one of these, take the pod off and make sure the diaphragm is properly installed and sealed. When you re-install it, make sure the sealing washer is present.
>Set the fuel level.
>Finally, reset the mixture screws to in the center of their working range; 3/4 turn on Holley-types, 2turns on Carter-types
> Next, verify your TDC mark on the balancer is correct using a piston stop. This is very important on a used and factory balancer.
> reinstall the carb, prime it, start the engine; and on a Holley-type with fuel-level windows, check the wet and running fuel level. If you have a fuel-pressure gauge, you are looking for 3.5 to 4.5 psi.
>>Now; after this, do NOT touch the Idle speed screw!
>You will set the idle-speed to 500/550 in gear by adjusting the Ignition Timing to in the range of 8 to 14 degrees advance. And when you pop it into Neutral, you are looking for no more than a 100 rpm rise. If it rises more than this, take timing out.
Note-2
explanations on the tune
Ok to explain;
1) Your idle-timing changes your idle Power. As does your idle-speed, but more so the timing. The fact is that at idle, your engine actually wants more than 20/25 degrees. You cannot give her that for two reasons; 1) the rpm will climb out of sight, and 2) if you turn the speed screw down, you will shut off the transfers. So don't go there.
2) Your idle-timing can be very little, and the engine will idle just fine, altho with very little power to spare.
3) your job is to find the amount of Idle-power that does not cause a huge transmission bang when shifting from N/P to in gear. Yet a transfer-slot exposure on the lean side that does NOT cause a tip-in sag.
4) the mixture screws are just idle quality trimmers. The transfer slots are your low-speed/low-rpm primary fuel supply. The trimmers never shut off, so the richer they are, the richer the entire circuit is. You want the combination of the transfers plus the trimmers to be parked in a place that prevents a tip-in sag/hesitation. You cannot.should not expect the pumpshot to fix the tip-in sag, that is NOT what it is there for. Tip-in means slowly tipping-in the primaries as to take off naturally and normally. A hesitation here is extremely annoying. Your job is to find a combination of Idle-Timing and Curb-Idle adjustment, and Trimmer-adjustment that is just enough, and no more. I gave you the baseline tune to get you started.
If you change the wet fuel level, then you will have to re-tune.
If you change the fuel-pressure or fuel-type, you will have to change the tune.
If you change the running coolant temp, you will have to change the tune.
If you change the stall or rear gears, you may be able to you-guessed-it, re-tune.
If you pile the car full of 200pounders, you may have to re-tune lol, cause you may get a tip-in sag, lol.
If you just cannot get rid of the tip-in sag with the transfers set to square,and with the trimmers at or near baseline, THEN add transfer fuel by adjusting the curb-idle screw. If the Idle-speed gets to be too high, retard the timing. Then re-work the trimmers.
As for the pumpshot; No matter where you reset the curb-idle screw to, every time you change it, you have to check that the pump begins squirting at or near, the instant that the primary throttles move. There are adjustments for this. The pumpshot takes over when the speed/rate of throttle-opening is more than the transfers can handle. Insufficient pumpshot results in a bog, where the nose falls for an instant, when you floor it.
Ok that about wraps it up.
Hang on;
>If after going thru this routine, the idle-speed refuses to come down properly, then the engine is getting air somewhere not authorized by the throttle openings, go find it.
same as before;
Here are your usual suspects, in most likely order;
accidentally cracked or stuck-open secondaries
an un-capped vacuum port on the carb.
intake to head connection including in the valley under the intake
the carb base gasket(s)
a faulty PCV
any vacuum device running off the intake
a perforated diaphragm or broken control valve in the Brake booster
faulty guides
faulty exhaust valves
a hole in the plenum
Happy HotRodding