Map sensor reading too high

[Oleblu]

I completely agree with Fast4.7 the 5.7 vortec headed and lt1 engines do want more timing through the entire range. I am idling with 25-27* with the stock cam. and also have upwards of 30* WOT from 2800+ rpm. too low of timing will cause exhaust backfire but that usually only happens when you get into negative timing in close to idle area's. I went with a more aggressive approach and used a stock 97 corvette ls1 high octane timing map they seem to have timing closer to what our less efficient vortec/lt1 head design likes. For some reason they gave the first year LS1 corvette a shit ton of timing. I only run 90+oct fuel in my vortec headed truck. Which weights 4500lbs with me in it. and have tuned my truck rather aggressive in the timing area's. I tend to run richer fuel mixture with alot of timing for WOT. usually with little to no knock. now this works well with my vortec headed truck. My gen 4 5.3 tahoe likes less timing and a slightly leaner fuel mixture. its mostly in the combustion chamber and runner design i would think. older sbc heads would happily run 35-36* total timing by 3000 rpm. vortec/lt1 heads like slightly less around 30* for the most part. and the ls type heads like even less around 23-25* they are a much more efficient design.

[Fast4.7]

This is what I am running on an Express van with a 2,600 stalled 4L80E, 4.56 gears and a Lunati Hotcam.