I got my car back on the schools dyno, and made a few pulls. i made 10 HP over my TBI runs and the a/f mixture is better. but what is an ideal A/f mixture at WOT on a carbed 305. right now it's around 13:1 at 3250 and creeps down to 11.8:1 as it hits 5000. this is with stock heads and valvetrain and has a 600cfm edelbrock and weiand stealth DP manifold.

 

Well, my engine run's around 13 to 13.5 to 1 from 3000 to 5700. I would think 11.8 is safe but you could lean the engine out some with out a problem.

Auggie

 

Most engines make best power at between 12.7 and 13.2:1.

11.8:1 is too rich, it's costing you some power.

Typical for a too-small carb...

 

I'd hardly call a 600 cfm carb "too small" for a typical 305. 11.8 :1 is too rich, we all agree. However it's an incorrect assumption to think that carb size is the primary culprit. The primary culprit is that the 600 cfm Edelbrock needs a little tuning with regard to the secondary metering rods: They probably need to be lowered on a different hanger to help lean out the secondaries. A primary indicator of a "too small" carbuerator is if the MAP signal starts creeping away from 101 Kpa at wide-open throttle as RPM increases. Tuning and mixture are irrelevant to the overall size of the carb.

 

His Edelbrock has neither secondary metering rods, nor a hanger.

In theory, but in practice every carb has a designed range over which it is able to provide a linear increase in fuel with an increase in flow. Operating outside that range causes tuning headaches.

 

11.8 isn't terrible though. I'd leave it alone. The richness will keep your exhaust valves cooler. The power drop is only a percent or 2. It will also allow you to run a little more timing.

 

Thanks for all the input. i suppose i'll just have to wait till i can get a wideband for the car till i can tune it. my next thing is to try and get the ignition timing in line with what the engine needs.