Has anyone experience in ignition timing the L31 350? I used to have a L31 350 in my old 96 Suburban. I have a 94 Cadillac Fleetwood with the LT1 with RPO V4P (aka, 7000# tow package). The heads on the iron LT1 are virtually identical to the L31 Vortec. My 3.42's and shorter tires have the same overall effective gear ratio as the truck does with its 3.73's. So, with the weight of my Fleetwood empty at 4400 lbs and the truck at 5200 lbs. Shouldn't the overall ignition timing be darn close to the same?

So, when I look at the timing on my friend's 98 Suburban, it seems on average 10 degrees LOWER than my Cad. The Cad is a bullet compare to the Sub.

Shouldn't they be much closer to each other in tuning? Both are intended for 87 octane with iron heads. The LT1 having around 0.5 to 1 point more compression.

Or is this one of those cases where GM was just so pathetically conservative in the tune that the L31 just has a lot of power left untapped?