Isn't the purpose to ensure on cammed cars in particular they don't bog down, because camshafts push the power band higher in the rev range?
Even on stock cars it's well documented LS engines aren't amazing under 3.5k rpm, it's why 3.27 or 3.45 diff gears are used to assist that
The idea would be that assuming you aren't running crap quality small rear tyres, that you can launch harder thus improve potentially significantly your acceleration with say a 3k stall
Back in the day I ran Hoosier Quick Time rear tyres at the drags, I could drop the clutch in a manual at 6000rpm with minimal wheel spin. On road tyres, I had to feather the car off at around 2000rpm to minimise wheels spin. On the drag tyres we did an 11.30 and on street tyres I think 12.7 was the best time and was mostly just under a 13 second pass.
The idea of the high stall with an auto, is launching the car off the line at higher rpm where the camshaft is working and with a stock stall speed even with tyre grip, you're launching at 1500rpm way under the camshaft rev range. In a drag race, the high stall will produce a faster ET.
A few years ago, we played around with a VZ 6 litre LS engine in an Improved Production race car on E85 and really sharpened it up in the midrange tightening camshaft lobe centres to 106 degrees and using a single plane carby manifold and 4-barrel throttle body Motec ECU. On a road car with 98 that doesn't support LS compression ratios, lobe centre is a compromise with midrange potential lost on lobe centres at 114 degrees or wider in some cases that also improves idle quality. The typical LS flatness under 3,500rpm isn't easy to improve without better fuel.
Well, standard idle is around 550rpm, mine now idles very smoothly at 700. Pushing on the brakes is now back to where stock felt like and feels so much better.
Do you think perhaps in the tune up when it's in gear, the throttle is opening up more than it needs to be? 700rpm shouldn't be riding on the stall. I've had a couple on the dyno in gear with foot off the accelerator and brake, they will spin around to 1500rpm and those cammed autos would push on the brakes. Out of gear they'd idle at around 800rpm.
