A tuning tale: BLMs say lean, plugs say rich - ZR-1 Net Registry Forums

XfireZ51 · 10-30-2018

Trying to dial in the tune on the LT5. Just when I seem to be close to finalizing based on BLMs, I pull plugs and they don’t indicate what the BLMs are saying. Specifically, my plugs are a very dark brown suggesting the tune is rich but the BLMs are reading in the 133-135 range. I’m tuning to within a +/- of 3 to 128. The heads and top end have been ported, larger cams, and 3” exhaust w headers.
Here’s a pic of the NGK BKR5E-11 I am using. They’re gapped at .044”. The darker one is from the passenger side bank, the lighter from driver’s side.

10-30-2018	#1
XfireZ51 Join Date: May 2007 Location: Chicagoland, IL Posts: 9,708	A tuning tale: BLMs say lean, plugs say rich Trying to dial in the tune on the LT5. Just when I seem to be close to finalizing based on BLMs, I pull plugs and they don’t indicate what the BLMs are saying. Specifically, my plugs are a very dark brown suggesting the tune is rich but the BLMs are reading in the 133-135 range. I’m tuning to within a +/- of 3 to 128. The heads and top end have been ported, larger cams, and 3” exhaust w headers. Here’s a pic of the NGK BKR5E-11 I am using. They’re gapped at .044”. The darker one is from the passenger side bank, the lighter from driver’s side. __________________ [SIGPIC][/SIGPIC]Former Membership Chairman Former ZR-1 Registry - BOD 1972 Corvette 4speed base Coupe SOLD long time ago 1984 Corvette Z-51/4+3 SOLD 1992 Corvette ZR-1 Aqua/Gray #474 SOLD 1992 Corvette ZR-1 Black Rose/Cognac #458 2014 Honda VFR Interceptor DX Last edited by XfireZ51; 03-08-2024 at 03:09 PM.