AJ/FormS said

While 90psi seems low, I would suspect the gauge is bad before condemning the engine.
If the cylinder pressure really is low, then so will be the "suction" on the intake stroke. This might make the engine run rich, as the air is in no hurry to plow down that 1920. An intake leak would only make it worse. As would running the engine at say 170 versus 200.
IMO all your problems are in the tune, with the possible exception of having an intake manifold leak. That engine should be able to tic over at 500rpm or less all the while smoking out every orifice and burning a quart of oil every other day. I had one like that so I know. Actually I have had two of them.
>So then, here is what I would do if it was mine;
If the engine is not running at or near 195, I would change the stat to make it so.
I would prove that the cylinders are NOT getting air from anywhere but the carb.
I would prove that the carb is being properly heated by the exhaust heating system.
I would pick a cylinder and make sure the piston is coming up on the compression stroke but not yet at the top; then I would bop the closed valves a few times to crush whatever carbon may be stuck on the seats. You will know when the valves are sealing by the change in the sound as the valves hit the seats. Then repeat on the other cylinders.
After that; I would run a chemical cleaner down the carb to get rid of that carbon , and put some in the gas-tank for good measure. Then warm it up and change the oil.
Then I would very accurately reset the lash to .013intake/.023exhaust, because I know slantys like these numbers.. After you get the tune right, you can go back to factory 10/20 if you so desire.
Finally, I would warm the engine up and repeat the compression test with a known-to-be-accurate screw-in gauge. and I would back it up with a wet-test.

Now the engine is ready to be tuned.
Firstly, you should know that a stumble is almost always caused by a lean tip-in.
Here are some of the causes;
> a cold-running engine; hence the 195 stat
> tight valve lash, hence .013/.023
> engine already sucking air Not from thru the carb, and carb adjusted to compensate. hence the test
> Lack of carburator heat on a carb that was engineered to run it.....
> A low WET fuel level, and/or stale or contaminated gas.
> Insufficient transfer-slot exposure causing the transfers to stop or nearly stop flowing. This is nearly always brought on by too much Idle-Timing.
> insufficient pump-shot or a faulty pump-circuit.
> wrong and uncompensated air filter house.
> pollution controlled and delayed spark timing.
> a poorly functioning bowl-vent
> a poorly functioning tank-vent system.
> fuel-pump sucking air.
there may be more, but I got a brain-stall cuz it's lunchtime, and mabelly is distracting the concentration right outta me.

I can tell you that, even at 90psi, I am very confident that your engine can be tuned to eliminate that stumble; unless
1) your TC is defective
2) you are running a sub 2.76 rear gear
3) your brakes are locked, or
4) you are hooked up to 10,000 pounds of cargo trailer,lol.
The upshot of this is that from a stop, when you gas it; the rpm has to jump up to the stall-rpm and the car has to start moving, If it doesn't, then you can have problems, even with a well-tuned system.

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