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Thread: Lean issue with AFR appearing correct.

  1. #1

    Default Lean issue with AFR appearing correct.

    I'm running into a lean issue, which in turn is causing excessive water temps. The AFR appears correct, but when I pull the plugs they are white and my coolant temperatures are skyrocketing. The coolant system is new (cleaned water passages in block, Cold Case aluminum radiator, Flex-A-Lite 185 Black Magic electric fan, flow cooler water pump, divider plate clearance adjusted (Pontiac 474ci motor), various thermostats used 160°, 180°, 195°, spring in lower hose, radiator burped correctly). Engine specs: Butler Performance forged stroker kit for 455 Pontiac, which puts it at 474ci, Edelbrock Performer heads, compression ratio 10:1, 1.52 rocker arms, Comp Cams CCA-51-224-4 Hydraulic Cam (230° int./236° exh, 0.488" int./0.491" exh), Performer RPM intake, Hedman shorty headers into Flowmaster exhaust, Bowtie overdrives Stage II 200-4R transmission, 2500 stall torque converter with cooling lines going into Cold Case radiator, Holley Dual Sync distributor (controlling timing). This is a cookie cutter Butler Performance engine build which results in 500 HP, 550 lb/ft torque. I'm also running a Vintage Air system with a 6-1/8" water pump pulley. I've tried various thermostats, changed WOT timing from 36° down to 32°. I continue to see water temps climb to almost 240° in stop and go traffic after about 20-30 minutes of driving in 80° temperatures. I also live at a 4500' elevation. All my plugs are white. The AFR tables in the datalogs look good with a 13.5 - 14.2 cruise, 12-12.5 WOT, but it appears the engine is running extremely lean regardless. Could this be a WBO2 sensor issue? When I was setting up the system I had a bunch of headers leaks and exhaust leaks which caused an excessive rich condition (ruining the new Champion RC12YC). I put in a new set of Champion RC12YC plugs after fixing all the exhaust leaks. Any thoughts on this issue would be greatly appreciated. I've attached my base configuration (Progressive linkage fix with AE vs TPS adjusted, and tip-in set) and last datalog. Also, since new the Learn Table shows 0% (separate post) when pulling the SD card from handheld and opening with the PC software.
    Attached Files Attached Files

  2. #2
    Join Date
    May 2019


    Excessive richness can foul the WBO2 sensor. How long it takes, I'm not sure.

  3. #3


    What's the best method to enrich the AFR? I was just lowering the AFR by .5 in the handheld, but the plugs are still white (which is strange, since I live at 4500'). Also, MAP shows 86 kPA when the engine is cold.

  4. #4


    I can't help with the tuning questions, but 86 kPa is what I'd expect to see for MAP at 4500 feet with engine not running (based on elevation and 80°F ambient temp). If you're seeing MAP at 86 kPa when running, that seems bad.

  5. #5


    Could be a tough one to solve. First step would be to replace the wideband O2 sensor. Hopefully that solve the issue. If it doesn't, then you might be in for a slog. Wideband O2 sensors don't usually fail with a fixed offset, so I have a hunch that you have something else wrong. But might as well do the easy test first and then go from there. Welcome to EFI debugging 101.

  6. #6


    I think part of your overheating problem is that Flex-A-Lite 185 Black Magic electric fan. Way too small for a big block, IMO. I had one on my 4.3L V6 Blazer and it can't keep it any kind of cool in the summer heat. And it didn't have a chance if I turned the A/C on. On my 748 RWHP twin turbo 400 SBC I use these dual Spal fans and the engine never sees more than 185°F in the 100°F Texas summers. And now with my 1250 Super Sniper controlling the fans, about the only time the second fan kicks in is when I'm crawling along in traffic or sitting at a red light.

    Might want to try a cooler plug too. That RC12YC is a pretty hot plug. Hard to get color in plugs if they're too hot.
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    Last edited by djh61187; 07-29-2019 at 06:29 PM.

  7. #7


    I agree with this. I think a big part of your problem is airflow. That flex fan isn't pulling enough air across the radiator.

  8. #8


    I've got the matching Cold Case radiator fan on order (should've bought them as a kit when I purchased the radiator). Holley support requested I check the WBO2 sensor location from the collector (9"), then they had me check the fuel pressure at the inlet ($50 later it shows 60 PSI and goes up to 70ish during revving). I'll be calling them again today to see how they can help me with the lean issue.

  9. #9


    Any idea why the fuel pressure goes up when you rev the engine?
    69 Camaro
    400 SBC, ProCharger D1SC

  10. #10


    It doesn't stay at 70ish when revving, only spikes up there and drops back to 60 psi. It stays right at 60 psi. I'll be changing to a colder range of plugs to see if that helps.

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