afr numbers

[dougs bs23]

after battling my qf hr 680 for a while and not getting this thing right,  I discovered after talking with lunati its to small.  So, I picked up a preform street series 750, right out of the box I see a great improvement.  this only corner adjusts on the primary side/ vac secondary.  iab 70, hsb 33 primary and secondaries are all 4 33's.  pri jet 72, secondary jet 78  Set floats to mid glass, adjust idle to 950 Seems where it wants to run the best.    timing at 16* vac at 13 hg.  afr numbers are idle in N 13.2 in drive 13.8 cruise at 40 mph as high as 15.6  (digital afr gauge)  seems to load up and pig rich on take off from a light or stop sign drops to high 11's then comes back up to mid/upper 13 range at cruise)  so I change iab to a 71 idles in d at 12.8 cruise at 13.8 to low 14's.   a quick wot, drops to low 12's then climbs to high 14's low 15's.    I think im close but am looking for all the expert advice on where it should be,   70 cast 340, eddy airgap intake doughs headers with x pipe lunati camlift 494/513, dur @ 50 226/234 advertised 271/279   am I getting close,leave it like it is?   or keep working it out?

[Strawdawg]

Not sure that i understand all your abbreviations, but, It's pretty close everywhere except at launch, it seems.

I would make sure that I checked the power valves and see if they are appropriate for your in gear vacuum.  Then I would consider slowing down the accelerator pump shot so it adds less initially.

I would aim for an a/f of 12.5-13.0 when the throttle is wide open.  Remember that when you first hit it, you get enrichment from the powervalves and from the accelerator...then after that, it boils down to the power valves plus the jet sizes.

Cruise and idle sound fine to me.

[dougs bs23]

 Power valve is 6.5. So to slow down the pump shot would changing the cam be what I'm looking for. It's currently red. Would I go to white?  I'm not sure how the color codes of the cams go but I do have a full set of them

[Chryco Psycho]

this should help https://www.google.com/search?q=holley+pump+cam+chart&espv=2&biw=1366&bih=643&tbm=isch&tbo=u&source=univ&sa=X&ved=0CBsQsARqFQoTCNvv_eGmicgCFQvXHgod7KcLoA
 what you have to keep in mind is some cams pump more or less / degree of throttle shft rotation too , so you may get a minimal shot @ 10* but get a lot more with 45* , or the other way around not just total volume , white is a smaller cam than what you are using BTW

[Strawdawg]

Normal power valve starting points are half the idle vacuum...in gear for an automatic...so your 6.5 would be a good starting point for an idle vacuum of 13 "/hg

[bandt]

Just letting you know the higher the afr # the leaner the mixture.

[dougs bs23]

so my cruise, wot and idle in gear numbers look good, so I just need to tweak the launch a little,  maybe by pump cam or pump linkages  btw elec fuel pump at 6.5 psi  maybe that's a little to high?   when I get the time ill lok at the pump linkage adjustment and go to a pink cam

[Strawdawg]

so my cruise, wot and idle in gear numbers look good, so I just need to tweak the launch a little,  maybe by pump cam or pump linkages  btw elec fuel pump at 6.5 psi  maybe that's a little to high?   when I get the time ill lok at the pump linkage adjustment and go to a pink cam

6.5 is too high if your vacuum in gear at idle is something like 8 "hg.  If your idle vaccum is 13 as I stated earlier, then it is probably okay.

I always try to get the pv right before proceeding.  Your cruise a/f sounds good.  Your idle a/f is not too bad if you have a steady idle.

[YO7_A66]

 ""iab 70, hsb 33 primary and secondaries are all 4 33's.  pri jet 72, secondary jet 78  Set floats to mid glass"
""timing at 16* vac at 13 hg.  afr numbers are idle in N 13.2 in drive 13.8 cruise at 40 mph as high as 15.6""
"" seems to load up and pig rich on take off from a light or stop sign drops to high 11's then comes back up to mid/upper 13 range at cruise)""
""so I change iab to a 71 idles in d at 12.8 cruise at 13.8 to low 14's.   a quick wot, drops to low 12's then climbs to high 14's low 15's.""

 - Start with setting your idle A/F in gear. Aim for 13.6-14.2 to see where the engine idles best. (Use your metering screws)
 - Then from a SLOW take off, look at your A/F and adjust your pump cam/squirter to get you into the 13's. (If you swap pump cams, you need to reset the pump arm bolt/nut each time so that fuel squirts out as soon as you move the throttle at idle).
 - Then check your steady cruising speeds of 30-70mph and write down the A/F numbers (30,40,50,60,70mph). Aim for 13.8-14.4 or so. If you write down the A/F at each one of these steady mph readings, this will tell you the whole story of which circuit you need to tune. (30-50mph'ish will be your Idle Air Bleeds, 50mph'ish up to 70mph will be your Main Jets. Each time you swap out your IAB's, you will need to reset your Metering Screws for best idle).
 - Then from a steady cruise (30-50mph), push the pedal down to accel (not WOT) to open the mains and look at the A/F. Aim for the low 13's or so. This is your Power Valve and your Power Valve Channel Restricters.

 I have attached a pump cam chart for your reference. Hopefully you can read it. Notice on the left side (up to down) shows throttle degrees of rotation. Then each pump cam (50cc cams are yellow and brown. The rest are the 30cc cams) shows a number at that degree. Just use these numbers as reference numbers to make it simple.
 EXAMPLE: Blue cam at 30 degrees shows .218. Pink cam at 30 degrees shows .110.  This tells you that the Blue cam delivers 1.9% more fuel at 30 degrees of throttle opening than the Pink cam.
 Then use this chart to figure out which cam to test. If you need more or less fuel at 20%, then look at the chart at the other colors and reference their 20% numbers for more/less fuel. Then test that cam.
 

[cudabob496]

ignore some AFR numbers till everything warmed up

[734406pk]

""iab 70, hsb 33 primary and secondaries are all 4 33's.  pri jet 72, secondary jet 78  Set floats to mid glass"
""timing at 16* vac at 13 hg.  afr numbers are idle in N 13.2 in drive 13.8 cruise at 40 mph as high as 15.6""
"" seems to load up and pig rich on take off from a light or stop sign drops to high 11's then comes back up to mid/upper 13 range at cruise)""
""so I change iab to a 71 idles in d at 12.8 cruise at 13.8 to low 14's.   a quick wot, drops to low 12's then climbs to high 14's low 15's.""

 - Start with setting your idle A/F in gear. Aim for 13.6-14.2 to see where the engine idles best. (Use your metering screws)
 - Then from a SLOW take off, look at your A/F and adjust your pump cam/squirter to get you into the 13's. (If you swap pump cams, you need to reset the pump arm bolt/nut each time so that fuel squirts out as soon as you move the throttle at idle).
 - Then check your steady cruising speeds of 30-70mph and write down the A/F numbers (30,40,50,60,70mph). Aim for 13.8-14.4 or so. If you write down the A/F at each one of these steady mph readings, this will tell you the whole story of which circuit you need to tune. (30-50mph'ish will be your Idle Air Bleeds, 50mph'ish up to 70mph will be your Main Jets. Each time you swap out your IAB's, you will need to reset your Metering Screws for best idle).
 - Then from a steady cruise (30-50mph), push the pedal down to accel (not WOT) to open the mains and look at the A/F. Aim for the low 13's or so. This is your Power Valve and your Power Valve Channel Restricters.

 I have attached a pump cam chart for your reference. Hopefully you can read it. Notice on the left side (up to down) shows throttle degrees of rotation. Then each pump cam (50cc cams are yellow and brown. The rest are the 30cc cams) shows a number at that degree. Just use these numbers as reference numbers to make it simple.
 EXAMPLE: Blue cam at 30 degrees shows .218. Pink cam at 30 degrees shows .110.  This tells you that the Blue cam delivers 1.9% more fuel at 30 degrees of throttle opening than the Pink cam.
 Then use this chart to figure out which cam to test. If you need more or less fuel at 20%, then look at the chart at the other colors and reference their 20% numbers for more/less fuel. Then test that cam.

That's a nice chart to have!

[cudabob496]

as outside air gets cooler, AFR should go up I would think.

[dougs bs23]

got to mess with this a little today before work, in gear vac at idle is 11,  went to a 73 iab and reset the corners for best idle without touching the idle adjust screw.  Going through all the speed ranges from 30 to 50 now my numbers are all in the high 14's to as much as 15.1  maybe a little to lean but seems to run good and doesn't seem to load up on takeoff from a stop sign or light and merging in traffic.    I think im getting closer,  may have to open the corner screws a little, maybe less than 1/8 turn to richen uo just a hair. 

[734406pk]

Looks like you've got it dialed in nicely!

[Strawdawg]

Good job!

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