You nailed that deal down, and why I use and prefer to run less timing at idle and throttle plates opened a tad further. I can superficially tune most set-ups for smoother idle by adding a butt-ton of timing at idle, but many will have the throttle plates so far closed that it becomes difficult to establish a stable idle in and out of gear when a slight load is placed on the engine. I want to see very little RPM drop when the trans is placed in gear, and rock solid idle quality in gear when the vehicle is stopped. This only happens when final tuning is done with the engine fully heat soaked.
One major problem I see here with troubled vehicles brought for custom tuning is some "creep" in the advance curve right at idle speed. If you have spring in the mechanical advance that are allowing any timing in at idle speed it's going to be difficult to tune and you will see much greater RPM changes in and out of gear. You'd be surprised how many vehicles have been brought here for carburetors issues that were fixed by putting stronger springs in the distributor or throwing all that imported advance curve crap out and putting stock parts back in them......Cliff
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https://cliffshighperformance.com/
73 Ventura, SOLD 455, 3740lbs, 11.30's at 120mph, 1977 Pontiac Q-jet, HO intake, HEI, 10" converter, 3.42 gears, DOT's, 7.20's at 96mph and still WAY under the roll bar rule. Best ET to date 7.18 at 97MPH (1/8th mile),
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