All your personal opinion Bear. I know several guys that run the 4180 including 5.0 people and found it to be a very good carburetor. My 4180 has 95,000 miles on it and gets between 10 and 12 mpg running down the highway. I think it runs as good as I can expect. Now, if you run headers and have "pulled all the emission junk" off your motor then there is no telling what the calibration requirement is for your engine. All bets are off and it's up to you to derive a "properly set up Holley 4160". I've seen my share of messed up Holleys and sadly it usually starts with the purchase of the Holley Trick Kit.

 

I changed from the 2 stage p/v to a 6.5 many moons ago. With the 2 stage, it will allow partial extra fuel starting at 10 inches of vacuum and the full amount at 5 inches. In theory, it will burn less fuel with a single stage p/v. I checked my milage just once and it got 13 mpg unloaded easy on the throttle steady 55 mph......YMMV!

 

But a single stage is either all the way on or off. When towing a really heavy load, having the power valve open in stages is better. It's like your whole carb, you don't want only idle or WOT do you? You want to vary it. Oh and all 2 stage power valve don't open at 10" and 5" of vacuum. You can get different ones to match you setup. I preferred 10.5 and 5.5 model myself.

Two-Stage* (includes gasket)
1ST STAGE 2ND STAGE
PART # OPENING OPENING
Model 4160
125-206 12.5" Hg 5.5" Hg
125-207 10.5" Hg 5.0" Hg
125-208 10.5" Hg 5.5" Hg
125-213 11.5" Hg 5.0" Hg
Model 4175
125-209 11.0" Hg 6.0" Hg
125-210 9.0" Hg 2.5" Hg
125-211 10.5" Hg 5.5" Hg
125-212 12.0" Hg 6.5" Hg
125-215 10.0" Hg 6.0" Hg
125-216 8.0" Hg 1.5" Hg
125-65
* Two-stage power valves ARE NOT RECOMMENDED for performance applications.

 

I agree on some points. The original PV was a 10 & 5, I know there are others too. The truth be known, the differences, be it MPG or otherwise, probably won't add up to a hill of beans but, after 122K miles of RVing and 24 years of ownership, I can say that the single stage PV has worked very well for my application. Use whatever you feel comfortable with.

 

I found in my 92 f250hd, E4OD, 3.55's, peak mileage at about 75 to 80 mph, getting 17 imperial mpg which is like 12 or 13 us mpg if im not mistaken. Bed was full with a/c going and a tonneau cover which helped. Passing everyone going from winnipeg to hudsons bay saskatchewan. 1500 km round trip including an hour or 2 spent driuving in town. hope this helps