You got poor advice from the experienced engine builder and from Comp Cams.
The intake closing point is a critical event in an engine, and advancing camshafts closes the intake valve much earlier so everything above the piston starts to get compressed sooner, plus you change scavenging by the exhaust moving things ahead some.
Been hearing all sorts of remarks over the years about "advancing the cam to make more low end power" and to account for timing chain stretch, among other things. Those comments are mostly regurgitated information from very poorly informed folks and from doing this for many years I know that they have very limited experience with actually moving camshafts around and looking at the results....FWIW.
The cam you used was already on a tight LSA with an advanced intake lobe position so moving it further ahead obviously was not a good move since you have high cranking pressure and the engine doesn't like much initial timing. It shows 292 degrees duration @ .006" tappet lift and 232 @ .050", so it's PLENTY of cam for what you are doing. It shouldn't be making a lot of cranking pressure or finicky to a lot of initial timing either being on a tight LSA and sporting a lot of seat timing.
Not a big secret here or anywhere else that I'm not a big fan of tight LSA camshafts in "street" engines. They are done that way for the "bling" factor more than anything else. Folks love to hear the miss-fire in the exhaust or "lope", but at the same time they narrow the power curve, pull power down in the rpm range, increase octane requirements, and put a lot of unburned fuel out the exhaust (stinky).
Cam position also effects idle quality to some degree, as well as efficiency, power output, and vehicle performance.
Difficult cranking when hot, "kicking back", and breaking starters with as little at 8-9 degrees initial timing is a HUGE indicator the camshaft is too far advanced, or your actual compression ratio is much higher than predicted, or a little of both.
From what I've seen tuning engine with similar characteristics, it will also be finicky with the timing curve, total timing, and how much timing you can add by the VA at cruise as well.
For idle tuning you simply have to get enough fuel to the mixture screws to provide full control from rich to lean, and enough bypass air to keep it on the idle system (no nozzle drip).
Many late model carburetors, especially truck units will also have a LOT of idle transfer slot in the baseplate. This can provide a good amount of fuel to the idle system even if the mixture screws are seated, so it can make idle tuning a little more challenging.......Cliff
