WOT A/F ratio... what to aim for

[Canadian1968]

A few people already know my setup 
http://www.dodgecharger.com/forum/index.php/topic,121570.msg1511385.html#msg1511385

Made a few runs at the track this year, best ET of 13.45

One thing I want to change, or at least I think I should change is my WOT  A/F ratio. Have a wide band installed and get a reading of 10.8  at WOT . That is good for forced induction but not NA!!!
I have read that 12.5 is commonly used for peak power.  At the same time all motors are a bit different. 

Given the combo I have , Iron heads with stock valves and all that stuff.  Would 12.5 still be a good number to aim for ?

Cheers..

[firefighter3931]

I allways shoot for high 12's to low 13's at WOT. That 10.8 is killing ET for sure ! How do the plugs look ?


Ron

[Canadian1968]

To be honest haven pulled the plugs since the early break in period of the motor . 

Last trip out was a few good WOT stomps to verify my rich condition. So I will pull a few plugs and see what they look like.

[BSB67]

Jet for mph. 

After you've established the best mph, then put the gauge on.  You might be surprised.

[c00nhunterjoe]

  too many people relay on the computer to tell them what is best. Do you have 1 sensor pickup or 8? Where in the pipe is it/them. A few inches one way or the other can change what the gauge displays.... see where this is going? Nothing wrong with using the gauge as a tool, but dont use it as gospel.

[Canadian1968]

I got a metering block for the secondaries.   When I looked up the replacement metering plate , it was advertised as having .81 main hole and .31 idea hole.

Is the 81 a direct compareison to a jet size ? If I wanted the same I could install a pair of 81 jets seems pretty big !?

Just trying to figure oUT where to start with jet size. I know the conversion kit sold on summit comes with 76 jets ?

[BSB67]

For clarification.  Are you talking about a 0.081" hole in the metering plate?

Holley jet #74 has a 0.081" hole,  Holley jet #76 has a 0.084" hole.

This is a reasonable stating point, but hole size is not the only aspect of the "orifice" design that effects flow.

[Canadian1968]

yes sorry missed the the "0" . The plate has a main hole of .081.  If that is equivalent to 74 jet, then I would want to start of smaller ?

Since I am running very rich at 10.8. Maybe a set of 72 jets would be good .

[BSB67]

I've lost track.  What carb?

If you had a plate before, and you now have a metering block with jets and a power valve, maybe start with a power valve plug, and put the #74s in.  Drive it, collect some data, make some decisions.

If you are confident in your data, it is consistent and repeatable and you confident in your interpretation of your data, I would consider maybe going to an 11.8 now, and then start your testing and jet tuning at the track for best mph.  Let the A/F fall where it may.

Also, I think you understand that there are three primary contributors to WOT fuel metering, assuming the rear PV is plugged.  You need to first get steady state cruise right (primary jet and possibly IFR, depending on rpm), part throttle acceleration (PVCR) then the WOT with secondary jet.

[Canadian1968]

The carb is the classic 750 - 3310 carb.  Choke horn has been removed , inlets filled and radius, shaved the butterfly bolts.

Carb has been tuned quite a bit, I ended up with stock  #72 jets , #35 pump nozzel , 5.5 power valve,  a,green pump cam and second lightest spring for the secondaries  . Everything is on point , idle can be set at will. Cruise is 13.8 , nice crisp throttle response with zero bog. The only thing I was/ am not happy with is the WOT. It was 10.5 range , removing choke horn and other mods brought it to 10.8 but still way to rich.

But with 3310 that's where I was stuck with the metering plate.  I now have a metering plate with power valve block off . So I am just playing with the jets . As discussed given eveything should stay the same I just need to worry about the jet sizing . And the . 081 hole in the original metering plate is a #74 jet i feel the # 72 is what I will start with?

[c00nhunterjoe]

Start with the same jets and go from there.