Safe A/F ratio on run in?

[Dan1200sss]

after 2years of slowly gathering parts and building up a fairly angry wee ca for my datsun 510...it's finally time to turn the key and start running it in. What Air fuel ratio should I be aiming for to avoid bore washing? Also with the ARP head studs do I retorque them after a heat cycle? Or are they fine to be left as is ( The head gasket is a 1.5mm Tomei MLS ) and yea any advice/tips on running in a ca18det will be greatly appreciated

[float_6969]

target AFR should be between 12-12.5

YES, they need re-tourqued. At least mine did. I think I had to tighten them down twice actually.

[Dan1200sss]

Cool, so that target AFR is at idle/cruise or on boost?

[float_6969]

WOT. If you're running a stock ECU, it'll keep the AFR @ idle and cruise around 14.7:1. If it's a standalone, then idle will be around 12:1, and I run mine at about 16:1 at cruise for gas mileage purposes. It's not the best for emissions though. Lots of NOx when you do that. I did find that if the butterfly valves are working, and you have them closed while cruising on the highway, I could run about 18:1 and still not have any running issues. At that AFR, your emissions are the same, if not better than at 14.7:1 and you get way better fuel economy. It didn't work w/out the butterfly valves though. I think the port velocities are too low w/them open and there wasn't enough swirl in the combustion chamber to keep the flame front propagating like it needs to.

This is all on gasoline BTW. I haven't had a chance to do any economy/emissions tuning w/E85 yet.