holley 5200 or 1975 carter maverick carb on a 170?

[early ford fan]

i have a rebuilt 170 with a cut 1978 head.i currently have the rebuilt 5200 from stovebolt with their adapter.i want maximum mpgs in my econovan,but the last time i check it i got 12.5 mpg.i installed an oxygen senser in the exhaust manifold hooked to a guage.the mixture is all over the place.i also have a vacuum guage.when im going down the interstate and start up a hill.i have the be careful pressing on the gas because the vacuum drops and i lose power.i can let off on the gas and when the vacuum gets back above 10 pounds i get a burst of power.i put a kit in it but nothing changed.i thought about rejetting to jet sizes ive seen posted on this site but im still not sure where to get jets.i called stovebolt but he said he had very few sizes left.i have a carter carb off a maverick.if i through a kit in it would this carb work well?btw i also have the duraspark 11.

 

[cobraguy]

I got mine at
www.redlineweber.com

 

[early ford fan]

i sent them an email.thanks.

 

[Harte3]

If you are using the less expensive narrow band 02 sensor/gauge it will not be much more than a light show. It will show steady lean or rich but anything in between and it just flutters back and forth. It's good for a general idea of AFR but certainly not definitive. On mine the vac has to drop to less than 8 hg under load before there is any indication of some enrichment (rich) on the gauge showing that the power valve on my carb is opening.

 

[cobraguy]

You need to know what you want when you order from redline. I couldn't get any tech advice from them.

 

[early ford fan]

they say they can send me a jet pak that will get me into the ballpark,but recommend i get a weber instead because it will give me 10-12 percent better gas mileage.the guage is an autometer pro comp.around town it generally stays way in the green,but on the interstateat a steady speed i have to back off the gas sometimes to keep it from pegging red.

 

[Harte3]

Now I am wondering...IIRC my Summit gauge reads Red=Lean, Yellow=Stoich, and Green = Rich...and at cruise it definitely runs Red and at idle it runs Green. When I push the throttle I'll get a Stoich/Rich blip indicating to me the pump squirter is working and when I push it hard enough to drop the vac below 8 hg it will go from Lean to Stoich/Rich which indicates the PV is opening and back to Stoich then Lean as the engine speed and air flow pick up and hg in the manifold rises. Depending on speed and throttle position I can make it run Stoich but at the lower speeds around town like at 30-35 mph my speed will slowly increase if I hold it at Stoich. It apparently likes a lean burn...which is good for mpg and as long as I don't get any lean stumbles/misfires it's good to go. All this depends on whether I am interpreting correctly what the gauges are indicating.

This is with the Holley 4v in my signature and I have made the adjustments in it to run the way I want but I don't know what is necessary for adjusting the curve in a 5200. I assume you want a lean burn for cruise conditions and mpg and sufficient enrichment of the mix when under load. Keep track of what the gauges tell you under different conditions and with some "trial n ordeal" you should get there.