OK, I'll bite
remind me why I should care about idle-speed in gear, with an automatic?
I mean;
> If it hesitates on take off, you just open the throttle a hair, to get some Transfer fuel, and drive
> if it wants to stall as you come to a stop, you just put it into Park, hop out, change the curb-idle a hair, and get back in, and drive.
> if it begins to pull too hard atta stop, you just retard the timing about 3 degrees, and Drive.
> If it clangs the sunshell on engagement, you probably got too much idle-advance, and/or too much throttle-opening.
>same if it wants to run-on after you shut the key off.
> if it's hard to start when cold; then probably she's not getting enough Transfer fuel, on account of the Idle-Timing is too much
>If it's hard to start when hot; then probably, she's getting too much Transfer fuel.
> when it goes;
click,vroom-vroom, when up to temp, with a mini-starter,
AND has no tip-in sag on drive-away,
AND does not clang or bang the trans when going into gear,
THEN, you got it just right no matter what the timing light says; Congratulations.
This, for a streeter with a cam up to 292/292/108, the biggest SBM cam I have tuned.
For a streeter with a modified engine, there is no magic fixed amount of Idle Advance. You just set the T-slots where they need to be, and when you get it right, it will idle, even at 5 measely degrees, and will drive away with no tip-in sag. The first time the engine actually cares about Ignition Timing is at or near it's stall-speed. and it can usually be all-in by 3500. Usually.
BTW-1
if the exhaust burns your eyes, the engine is wanting some Idle-Air bypass. Increasing the throttle-opening will not cure this, cuz that action will simultaneously increase the Transfer fuel.
BTW-2
IMHO, the best way to get bypass air is to drill a hole in each Primary throttle-plate. Thus, as you tip-in the throttles, the holes progressively stop flowing.
I put the holes inbetween the Transfers and the Idle discharge ports, and a good quarter inch back from the edge. In this way that air will be mixed with the fuel, as it passes by.
When this is done, the idle-speed will go up, and the ONLY way to reduce it, is by reducing the Idle-Timing.
Another way to introduce bypass air, is through the already existing, PCV circuit. This has the side benefit of being easily back-tracked, and fine-tuned. But, it never shuts off..... so you may need to service your breather more often, or, you can plumb the system to the clean-air side of your air-filter housing, as the factory used to do..
BTW-3
as for the size of the holes; this will depend principally, on the size of the cam. The bigger the holes, the higher the idle-speed will go, and the more the timing will need to be retarded. This is thus, not a contest. You only make the two holes just big enough to not have the stinky eye-burning exhaust.
I start at 1/16, and stop at 7/32. I went to 1/8 in the learning process, with the 292 cam, which was too much. I had to solder the holes shut, move over, and start again, Do not try to reuse soldered up holes, the solder will just end up falling out. In my case, the solder bit was never found nor any damage done
which is why I choose solder.
Good luck!
