Chevvy SS
July 24th, 2012, 07:58 PM
Of the many 6L VEs that I’ve tuned, I’ve encountered two with a peculiar tendency to run on or close to the low octane timing map particularly at full throttle.
One car is a standard manual except for branches, a free flow exhaust and an OTR aircleaner. It will not allow more than ~12 deg timing from 3600 to 6200 rpm on pump fuel. Not one of the many tweaks and changes I tried fixed the problem and no DTCs were recorded. The only way to get decent power was to force the timing up to ~18 deg by increasing the low octane map to almost equal the high octane map. No knocking occurred when this was done.
The other car is a modified 402 auto with trick heads 11:1 compression, branches, free flow exhaust, cold air induction, ARP conrod bolts and compcam with ~ 280 degrees duration at .005” lift and 113 degrees lobe separation. It will not allow more than ~17-18 deg timing in the 4000 to 6800 rpm range even though this type of modification usually requires ~24-26 deg of timing for best power. Aviation fuel is used.
Incidentally, both are 2008 builds with the same OS 12612381.
Any advice will be appreciated.
One car is a standard manual except for branches, a free flow exhaust and an OTR aircleaner. It will not allow more than ~12 deg timing from 3600 to 6200 rpm on pump fuel. Not one of the many tweaks and changes I tried fixed the problem and no DTCs were recorded. The only way to get decent power was to force the timing up to ~18 deg by increasing the low octane map to almost equal the high octane map. No knocking occurred when this was done.
The other car is a modified 402 auto with trick heads 11:1 compression, branches, free flow exhaust, cold air induction, ARP conrod bolts and compcam with ~ 280 degrees duration at .005” lift and 113 degrees lobe separation. It will not allow more than ~17-18 deg timing in the 4000 to 6800 rpm range even though this type of modification usually requires ~24-26 deg of timing for best power. Aviation fuel is used.
Incidentally, both are 2008 builds with the same OS 12612381.
Any advice will be appreciated.