What kind of AFR should I have on this 396?
11-15-2010, 11:00 PM
#1
What kind of AFR should I have on this 396? I hooked up an LM1 to my tail pipe and ran my car down the highway. I was seeing around 15-16 at no throttle and I'm not pulling any timing according to datamaster. Under full throttle pulls I can get it to dip to 10.8. I know its pig rich under heavy load. I have the FPR sitting at 40 at idle and with the vacuum off its at around 42-44. Cam is .560+ and 230/240 with 107.5 center.
11-15-2010, 11:47 PM
#3
I'd lean it out to 14.7:1 at idle, shouldn't have any problems there with that baby cam 
I'd start with the timing at ~28 degrees, and increase until kpa stop decreasing. 28 degrees should be pretty close though. Cruising... To start I'd run it at 14.7:1 as well, timing should be roughly 38-40 degrees if you're safe on the compression side. Increase timing until your kpa stop decreasing, then lean it out if you're comfortable with the fuel/compression you're running. I was running 1.05 lambda at cruise on e85 and it liked it. Never really could distinguish between awful and terrible gas mileage so not sure how much leaning it out 5% helped 
Once you get the low map areas where you want them, start blending to the high map areas to keep you safe (rich). Then follow the same routine to lean it out/increase timing. IIRC I started richening it up around 70kpa, I was cruising at ~60.
I'd start with the timing at ~28 degrees, and increase until kpa stop decreasing. 28 degrees should be pretty close though. Cruising... To start I'd run it at 14.7:1 as well, timing should be roughly 38-40 degrees if you're safe on the compression side. Increase timing until your kpa stop decreasing, then lean it out if you're comfortable with the fuel/compression you're running. I was running 1.05 lambda at cruise on e85 and it liked it. Never really could distinguish between awful and terrible gas mileage so not sure how much leaning it out 5% helped Once you get the low map areas where you want them, start blending to the high map areas to keep you safe (rich). Then follow the same routine to lean it out/increase timing. IIRC I started richening it up around 70kpa, I was cruising at ~60.