"Why chase timing specs when the problem can be carb related only?"
WWWWEEEEELLLLLL, idle quality and overall performance, engine heating and other factors will e adversely affected if the timing is not correct, especially carb settings.
If I read correctly, you have INITIAL of 14 degrees, and idle of 28? TOO MANY IDLE DEGREES.
Engnes do not like more than 22 to 24 IDLE degrees of timing. So, how to get there with full manifold vacuum sourcng? Well, not so hard, stop down the vacuum advance degrees.
HOW? With an adjustable degrees stop scroll plate attached the right way, to the vacuum advance (works on both stock type and adjustable vacuum advances). Crane/FAST p/n 99619-1 (Summit, Jeg's) When mounted properly, this stop will give 2 crankshaft degrees per serration of the stop, or, can be set wide open, to locked out. Mountng is easy, drill.tap 8/32 screw hole, mount plate and screw/washer, cut off excessive threads on the bottom of the advance, install, set, go. done. Low cost, Crane plate, and the screw, washer from the hardware store is less than a five dollar bill.
That way, the initial of 14 would allow easy starting, and once the vacuum came up in the engine, the idle timing would go to 22, 24, whatever degrees you select setting the degrees stop to.
OK, wise guy, how do I do that? Well, sir, ask for the complete stop plate packet here: [email protected]
They are absolutely FREE, with NO STRINGS, and, YOU can do the mods all by yourself. Works on either GM points, or large HEI distributors.
There is one picture that shows a fixed steel srtap to the vacuum advance, and it is also OK, but not adjustable. Home made, low cost (two 6/32 hardware store screws).
To set the degrees stop with the home made stop, use these degrees specs:
8 degrees: .086 inch
10 degrees: .112 inch
12 degrees: .135 inch
As far as getting the mechanical curve right, you might try one of two things.
First, look at the weights and center plate under the rotor, you want weights marked 41, center marked 375. This will give you 22 crankshaft degrees of timing to add to the 4 initial, for a 36 degree total timing, just where you want it. These parts are from the Chevrolet ZZ crate engine series.
Second, most of the aftermarket HEI builders use these parts as their default parts, might ask one of them for a set, if you can't find reasonably priced OEM parts.
Do not use one of the large HEI "recurve kits" available, they are NOT for street applications. They are designed to delete the vacuum advance use, and jack the initial way up for DRAG RACE USE ONLY. However, the mechanical advance springs in those kits do work for street use.