Portable test lab in the Bronco

[blubuckaroo]

I've just finished assembling my portable AFR gauge.
I just took it out foe a spin and was surprised how close my jetting already was to the target. It's still a little fat, and I'll be doing some metering rod/jet changes today.
The vacuum gauge and tach let me know which circuit the carb should be running on at a particular load.
The hard part is keeping eyes on the road. I need a drag strip.

 

[Justafordguy]

So what ratio are you shooting for?

 

[pennyduke]

What speed are you using to get the reading? Are you still using a Edelbrock 500 cfm Carb? I'm about to do the same thing so I will be following...

 

[blubuckaroo]

Yes, I'm using an Edelbrock 1403 carb.
I'm shooting for:
Idle 13.7-14.2
cruise 13.3- 14
power 12.5
I'm still not sure about the secondaries. Edelbrock recommends jetting the secondaries to the same stage of as the primary power jet/metering rods.

We'll see how these targets work. I suspect though I'll be going to higher octane fuel when I lean it out. The engine runs about 9.7 compression, and I've had to back the timing off to 10 degrees from the 14 it was originally set at before the engine work.

One thing I can tell you though, setting the idle mixture to the AFR gauge really got rid of the stinky exhaust.

 

[pcf_mark]

Some tuning tips you may want to consider:

1) AFR at idle is almost useless - just aim for highest manifold vacuum. It may be 13.2 or 14.0.
2) Cruise you can get really lean - 15-16-17:1! But it will get finicky with the accelerator pump set up. You can measure the improvement in fuel mileage because you spend 85% of your time at cruise. How your power valve is set will determine if you can smoothly transition to power but timing (see below) is critical too.
3) Make sure your timing is correct first. Decent idle timing is pretty easy to get but changing the curve on a Ford is a pain. You can play around with vacuum advance easier which is what I did to make my mileage climb. I used 15-16:1 then pulled in plenty of vacuum advance to give it good throttle response when going from cruise to more power. This is where you still need to read the plugs. You can see how good your timing is on the ground strap of the plug.
4) If you have E10 or E15 in your area in winter you may need to reject. We run E10 all year around here but in winter we get oxygenated fuels and they need a rejet of 1-2 numbers and a little less timing. E10 changes your target AFR a bit.

You are going after it the right way - with instrumentation! Take good notes because if you get lost you can always back up one step and re-establish your baseline.

 

[blubuckaroo]

I love tuning on carbs, but my eyes aren't what they used to be.
I can read the jet sizes, but not the metering rods. I had to use my sweetie's lighted sewing magnafier. I even measured the rods with a veneer caliper just to be sure.
Then there are three teensie-weensie spring clips that have to come off to get the carb top off. A hemostat works good, but don't drop one of those. You'll never find it.

 

[Broncobowsher]

I dropped a narrow band O2 in the exhaust to plug the hole while getting stuff together for the holley Sniper. Picked up a free meter from Harbor Freight and wired it in. It was handy. I was also amazed at how close the old Edelbrock carb was. I could drive against the A/F and knew when to push a little harder and when to back off (for economy).

Put the sniper on and set the target cruise A/F to 14.9 and power around 13.5
It drives clean, but the timing is jacked. Still have an emissions curve and lost the vacuum advance when I did the progressive linkage. Cheated it a little with just adding a little too much base timing. The real fix will be letting the EFI control the timing. That should start in a week or so.

I was about to put the sniper on the floor and just hook up the wide band and drive it. But when I got close, I just wanted the EFI instead.

 

[blubuckaroo]

Some tuning tips you may want to consider:

1) AFR at idle is almost useless - just aim for highest manifold vacuum. It may be 13.2 or 14.0.
2) Cruise you can get really lean - 15-16-17:1! But it will get finicky with the accelerator pump set up. You can measure the improvement in fuel mileage because you spend 85% of your time at cruise. How your power valve is set will determine if you can smoothly transition to power but timing (see below) is critical too.
3) Make sure your timing is correct first. Decent idle timing is pretty easy to get but changing the curve on a Ford is a pain. You can play around with vacuum advance easier which is what I did to make my mileage climb. I used 15-16:1 then pulled in plenty of vacuum advance to give it good throttle response when going from cruise to more power. This is where you still need to read the plugs. You can see how good your timing is on the ground strap of the plug.
4) If you have E10 or E15 in your area in winter you may need to reject. We run E10 all year around here but in winter we get oxygenated fuels and they need a rejet of 1-2 numbers and a little less timing. E10 changes your target AFR a bit.

You are going after it the right way - with instrumentation! Take good notes because if you get lost you can always back up one step and re-establish your baseline.

1) Yes, I found the vacuum gauge and tachometer still is the most effective way to set the idle mixture.
2) This is where an Edelbrock carb shines. With a handful of pull-off springs, and a vacuum gauge, you can easily figure out where the lag is and which pair of springs to select to get you into the power circuit smoothly.
3) I had my distributor curve calibrated by "Reincarnation" in Tacoma. They take your engine specs, cam card, vehicle weight, tranny type, and gear ratio and set the mechanical and vacuum advance. They recommended 14 degrees initial advance as a starting point. I lowered mine to 12 degrees because of a little ping at hard throttle. I may bump it back up and switch to high octane gas. I haven't decided yet.
4) Good point about winter/summer fuel. I'll be keeping my ears pealed for a ping.
Where the Edelbrock carb is now is 3 stages lean from stock on the cruise & power circuits, and 1 stage lean on the secondaries.
No more smelly clothes, and it's peppier too. Out of the box, the carb was running quite fat.

 

[pcf_mark]

Throw up a few spark plug pictures when you get time. Once you don't stink you are getting close! Feel for surging at light throttle then you are too lean for cruise

 

[blubuckaroo]

Feel for surging at light throttle then you are too lean for cruise

That happened this afternoon!
It drove great yesterday, but today it did have some hesitation while cruising through our small town. I thought maybe the engine was still cold, and just needed a choke adjustment.
Thanks for the help.