Hot weather, AFR's

[Bird 426]

We are experiencing hot weather here in Illinois, plus high humidity. Took the car out yesterday after taking out the 195 thermostat and installing a 160 for the summer months. Engine temp is still still in the 180 + range. The AFR's have really changed. Driving at 2,500 rpm was high 14's to tickling low 15's before the heat came in. Now, it's in the low to mid 13's. What a change the weather can make!

 

[Don selleck]

interesting, humidity causing it? or the air temp? maybe both. Any noticeable change in engine performance?

 

[Bird 426]

Don't usually drive it hard, it always seemed to like rich, I didn't like rich and sooty plugs. 95 ° with very high humidity with a heat index of 110 does change things!

 

[Rich H.]

Experienced the same a few years ago.

I worked hard to set everything up for hot weather, dialed it in pretty well for the hot temps, then the weather cooled off slightly and then I found myself cruising around with 17:1 A/F. Was surprised how well it ran super lean but didn't leave it that way.