A box stock 4160 vs. a stock (rebuilt) 4180 - Head to Head Test (non-scientific)

[Jake Papageorge]

its a bit of a read, so if you live in the "twittersphere" consider yourself forewarned! When I have the time, I love to do this kind of stuff. I don't do it to start arguments or draw out the "know it all" crowd to start debating and nitpicking everything. I am just sharing some UNSCIENTIFIC observations that I have made on a subject I got involved in. I do this all the time with technicians during the school year, I wanted to share with those of you who might find some value in the observations. This was a very non-scientific comparison, but the outcome was different enough where I feel VERY confident in my conclusions. I am, however, no absolute expert in any of this, I do, however, have a lot of experience in working with carburetors. If you have questions, I'm happy to elaborate or expand! Just ask em!

I posted my displeasure with the fuel mileage of my truck in an earlier thread. I did not expect to have a fuel efficient pick up by any means folks, as past experience has taught me that a truck this heavy, that is as aerodynamic as a barn, weights over a ton and a half (according to PTS so take it easy guys!) with a pushrod engine this about as inefficient as an overhead valve engine could be would not be a fuel miser. Add to this the variable amounts of Ethanol in the fuel (which dramatically degrades fuel mileage), and I went into this restoration thinking maybe 10 to 14 mph under normal driving conditions was attainable. I was sorely disappointed!

When I pulled this truck out of the barn, it was 100% original, with it's original 4180 carb. The vacuum lines (of which you know there are MANY!) were on incorrectly, cracked, plugged up, just a mess! Someone tried to rebuild the original carb and simply not could not handle putting everything back the way it was when they were done. The EGR was inop (Ruptured diaphragm which meant vacuum leak) and a partially bricked upstream catalyst. I deleted the EGR and plated it, hollowed out the catalysts and properly routed ALL the vacuum lines to the OEM connections, replacing the broken/cracked units and validating the operation of all of the thermostatic vacuum switches. The final move was to put on a box-stock Holley 4160 with an electric choke. I have several of these laying around so it was just a matter of grabbing a box and putting it on! I got everything (Including the kickdown for the trans) hooked up, smoked the intake to make sure it was sealed up, and the truck ran great! Off for the test drive...................... The test involved exactly 2 cold starts and 11 warm starts (no choke involvement).

I actually feel like I could see the fuel gauge moving! I filled the tanks up to the point where the pump "popped" and reset the trip odometer using my local Marathon station. I took a fuel sample and got out my graduated cylinder. Alcohol content was approx. 13%. This was my general method of checking alcohol content:

The driving quality of the truck was great! It ran perfectly! Bla bla bla.....7 - 8 miles to the gallon on the average. Granted, I only did 1 tank of fuel, in the blistering heat, and did not restrict myself to just city or just highway, it was a pretty even mix of both. Not the most scientific test in the world, but good enough for my needs. I drove the tank until the engine started to sputter, forcing a fuel tank switch to the rear tank. It took 18.4 gallons to fill the tank initially.

Disgusted with this outcome, I came out here, started cryin about the mileage, and this brought on an interesting discussion, none the less, I was inspired to rebuild the 4180 and put it back on and test it. I am very adept and experienced at rebuilding carburetors, particularly this one! Back in the day, in my dealership days, I had to repair more than I could count, along with some of the other abortions that Ford tried on their fleet. The variable venturi comes to mind! LOL!!! But I knew how to make one of those AND one of these 4180's hum a precision tune!

I got a Standard Motor Parts rebuild kit which included the original style 2 stage power valve, a new choke pull of and secondary diaphragm, and all the other parts and pieces. One of my programming customers has an old school emersion tank, so I stripped this thing down, verified it had the original jets (close tolerance 62's) and the right secondary plate, and off to the cleaning tank.

I brought the parts back, and commenced to re-assembling the carb. The only modification I kept from the last guy who did it was that I left the check ball out of the secondary vacuum motor, just like he did. This is going to cause the secondary's to open and close more quickly than with the check ball, but I wanted to compare apples to apples. The secondary spring was the OEM unit, so again, off we go............

I put it on the truck, got it all adjusted (idle and crossover mixture, float levels, choke and idle speeds, throttle kicker, transmission kickdown. The kickdown thing was tough because I did not want to chop up the stock OEM kickdown rod, so I had to improvise a little for the 4160 and take another kickdown rod, cut it, weld a couple nuts in the ID, put a 5/16 piece of stud-stock with a couple jam nuts, and shorten it up by the carburetor to get the proper kickdown rod engagement for the C6.

I filled up with midgrade until the pump "popped" and commenced to go out and put this black buffalo through it's paces like the last time! With the mileage this thing was getting, I would not take long to get 150 miles on this thing! This test involved 3 cold starts and 10 warm starts with no choke involvement. The extra cold start was to get the choke adjustment just perfect!

The fuel mileage for the 4180 increased the fuels range to 228 miles which syphers out to approximately 12 mpg in mixed driving conditions. Relatively same ambient atmospheric conditions (hot and sticky!). Relatively the same alcohol content in the 2nd tank. When I ran the 2nd tank out, it took 18.5 to clunk the pump, so I used about the same amount of fuel.

4 mpg was a pretty impressive increase which would cause an engineer to say "how do you know the 4160 didn't have a problem? Other than the verify that ALL the settings were the same (other than the primary jets being 64 out of the box and the 4180 being 62 and a 6.5 power valve vs. a 2 stage power valve, etc). Float levels, choke settings, idle speed, everything else was the same! As for the "seat of your pants" comparison, this was pretty simple:

4180 had definitely has a smoother and more fluid feel when transitioning from idle to part to full throttle! No question about this!

4160 had a more aggressive feel when accelerating. Prior to starting this comparison, I could floor the 4160 from a stand still without a break torque and the wheels would break lose and produce smoke...NO PROBLEM! The 4180 just kind of got a "bark" and go!

You can set the idle at 600 rpm and floor the truck with the 4180 and immediately drop it to idle in gear (stab the throttle in gear) and it will ALWAYS return to a nice, even, consistent, smooth idle. The 4160's idle will sometimes fluctuate and sometimes, even stall if set at 600 rpm. At 800 RPM no stalling, but idle quality is noticeably not as good.

I would love to do this with a Holley Sniper throttle body, if not for the hassle of having to accommodate duel tanks and a FI system that requires a return rail.

A couple important citations here:

Physically switching from a 4180 to a 4160 is not as cut and dried as it may seem! A few obstacles to overcome (on a truck with a C6 automatic) are:

Fuel line modification

Having to switch the distributors ported vacuum source on the 4160 that does not behave at all like the ported vacuum source on the 4180. The 4180, at a 600 rpm idle, has about 5-6 inHg that climbs up to 15-18 at WOT. The 4160 has 0 vacuum at idle. You folks who know understand the subtleties of load and speed based advance systems (and I know there is at least one of you out there reading this) understand what that means! Having 5-6 InHg at idle vs. zero In/Hg at idle means vacuum advance is occurring at idle. This, to me, is kind of a bit of a game changer!

A SIMILAR choke arrangement, but not the same by any means! 4180 has a far superrior choke pull-off system, but is finicky! The choke-stat was not really meant to be monkied with on the 4180. The threshold on 4180 between "just right" and "not enough" can be tough to find because of the notchy behavior of the choke plate because of the choke pull-off.

going from 4 corner idle mixture (which is a pain to adjust and requires some skill) to front venturis only.

Kick down linkage "sweep" being different between the two requires some brainstorming with a C6, and with an AOD, a whole different set up altogether!

The vacuum operated throttle kicker for the AC had to go when switching to the 4160 because it simply will not fit properly nor does it have the same contact arrangements on the throttle from the 4180 to the 4160. Well.....at least MINE did!

Functionally, there are some dramatic internal design differences between the average 4180 and a 4160. I am not going to list them all, but if you really want to know, check out this great piece on the 4180. It is one of the best I have seen:

http://vb.foureyedpride.com/showthread.php?184976-Thorough-investigation-mapping-of-Holley-4180-s

Just thought I would share.

Oh...BTW....when the EGR valve shows up next week, if anyone is interested, I will do this 1 tank test again WITH the EGR installed!

 

[Gary Lewis]

That's an interesting comparison. And while 4 MPG sounds significant, it is actually a 50% increase when going from 8 to 12. And 12 MPG with a 460/C6 combo is excellent.

I'm not at all surprised that the 4160's MPG was poor. Out of the box I've found 4160's to be quite rich. Also, I've seen the same problem of not being able to get a stable idle on a 4160. So I was betting the 4180's MPG would be better, although I didn't expect 50% better.

I wonder what difference the EGR will make? Obviously it only comes in during high-vacuum conditions, but it might lean the 4160 out a bit.

[Jake Papageorge]

That's an interesting comparison. And while 4 MPG sounds significant, it is actually a 50% increase when going from 8 to 12. And 12 MPG with a 460/C6 combo is excellent.

I'm not at all surprised that the 4160's MPG was poor. Out of the box I've found 4160's to be quite rich. Also, I've seen the same problem of not being able to get a stable idle on a 4160. So I was betting the 4180's MPG would be better, although I didn't expect 50% better.

I wonder what difference the EGR will make? Obviously it only comes in during high-vacuum conditions, but it might lean the 4160 out a bit.

I dont think I will be testing with the 4160, but there are some interesting considerations when contemplating the effect EGR will have on the mileage. I can already guess the performance is going to suffer a bit, but lower combustion temp's might mitigate the nullification of some of the A/F mixture. I think I am going to hang an A/F meter on this thing before I put the EGR on. Now that the cat's are hollowed, I can just put a spud in the tailpipe. My goal is to get this thing to a firm 15 mpg, but it has to be able to pull 5K worth of trailer and race car so I don't want to sacrifice too much in the way of performance.

So I had this crazy idea....tell me what you think:

What if I used a fuel tank switch off of one of these things in reverse to switch the return rail on a Holley Sniper system? Connect it to the existing fuel tank switch so that when you switch tanks, the feed fuel switch pulls from the tank you select, but the secondary fuel tank switch would direct the return rail fuel to the tank your pulling from. I am just dying to put one of these snipers on here to see what it will do for mileage and performance. I can go without the kickdown. Any thoughts?

[Gary Lewis]

I dont think I will be testing with the 4160, but there are some interesting considerations when contemplating the effect EGR will have on the mileage. I can already guess the performance is going to suffer a bit, but lower combustion temp's might mitigate the nullification of some of the A/F mixture. I think I am going to hang an A/F meter on this thing before I put the EGR on. Now that the cat's are hollowed, I can just put a spud in the tailpipe. My goal is to get this thing to a firm 15 mpg, but it has to be able to pull 5K worth of trailer and race car so I don't want to sacrifice too much in the way of performance.

So I had this crazy idea....tell me what you think:

What if I used a fuel tank switch off of one of these things in reverse to switch the return rail on a Holley Sniper system? Connect it to the existing fuel tank switch so that when you switch tanks, the feed fuel switch pulls from the tank you select, but the secondary fuel tank switch would direct the return rail fuel to the tank your pulling from. I am just dying to put one of these snipers on here to see what it will do for mileage and performance. I can go without the kickdown. Any thoughts?

Doesn't the Sniper require a higher-pressure pump? I thought all EFI systems do, which is one of the reasons I converted to a mid-90's system with the fuel delivery modules.

Anyway, if you get that 460 to 15 MPG you'll be working a miracle.

[Jake Papageorge]

Doesn't the Sniper require a higher-pressure pump? I thought all EFI systems do, which is one of the reasons I converted to a mid-90's system with the fuel delivery modules.

Anyway, if you get that 460 to 15 MPG you'll be working a miracle.

Yes, but I was going to put the fuel pump ahead of the tank switching valve. 45 to 60 psi pump means the factory mechanical has to go!

My apologies, this 85 has a VIN H 351. Not a 460. Yea, I agree! If I could get a 460 to get 15 mpg, I would be in line for a Nobel! LOL!!!!

This is why I am so disappointed with the mileage of this thing! I had a 400M in a bronco that I had built to be fairly stout (418 lb/ft or torque on the engine dyno) that got better mileage than this thing and that truck had a cast iron 908 transfer case, a C6 and that all iron Modified with a solid front axle! That truck was heavier than this thing and it used less fuel!

[Gary Lewis]

Yes, but I was going to put the fuel pump ahead of the tank switching valve. 45 to 60 psi pump means the factory mechanical has to go!

My apologies, this 85 has a VIN H 351. Not a 460. Yea, I agree! If I could get a 460 to get 15 mpg, I would be in line for a Nobel! LOL!!!!

This is why I am so disappointed with the mileage of this thing! I had a 400M in a bronco that I had built to be fairly stout (418 lb/ft or torque on the engine dyno) that got better mileage than this thing and that truck had a cast iron 908 transfer case, a C6 and that all iron Modified with a solid front axle! That truck was heavier than this thing and it used less fuel!

Yes, the mechanical pump has to go. What I did was to put '96 tanks and FDM's in since you can still get those, and probably can for quite some time. That gives plenty of pressure for the EFI system.

As for the 15 MPG, even with a 351W it is going to be a challenge with the C6. The unlocked torque converter and lack of OD makes it very inefficient. But I'm at about 13 with my heavy 4wd F250 and a 460/ZF5 combo, so it is possible to do better than 12. And the 400 in Dad's truck should easily do 14 or more with the E4OD. So it can be done.

[LARIAT 85]

Yes, but I was going to put the fuel pump ahead of the tank switching valve. 45 to 60 psi pump means the factory mechanical has to go!

My apologies, this 85 has a VIN H 351. Not a 460. Yea, I agree! If I could get a 460 to get 15 mpg, I would be in line for a Nobel! LOL!!!!

This is why I am so disappointed with the mileage of this thing! I had a 400M in a bronco that I had built to be fairly stout (418 lb/ft or torque on the engine dyno) that got better mileage than this thing and that truck had a cast iron 908 transfer case, a C6 and that all iron Modified with a solid front axle! That truck was heavier than this thing and it used less fuel!

Thank you for this anaylsis. I really enjoyed reading that!

The results are just what I expected. So many people are quick to dismiss the Motorcraft [Holley] 4180 as an "emissions" carburetor that should be replaced. Yes, it is that - but the 4180 is also one of the most *precise* carburetors Ford ever built. The primaries have annular boosters, which atomize fuel almost as well as fuel injection. The 2-stage power valve is much more precise than a standard single stage. (I am actually surprised you manged to find one.) And like you said, the choke system found on the 4180 is far superior to any other found on aftermarket carburetors. Ford engineers knew what they were doing when they designed these. There is actually much more engineering with the stock carburetors than most people realize. Ford engineers took into account engine type, engine size, transmission type, emissions, and even vehicle weight when they designed each carburetor for their application. They may look the same on the outside, but these carburetors can be much different internally.

I strongly considered running a Motorcraft 4180 from a Mustang GT when I replaced the original feedback Motorcraft 2150 on Lucille. Against my better judgment, I decided on a brand-new Holley Street Avenger instead. It ran okay, but I never could seem to get it tuned just right. And it seemed to constantly need to be fiddled with. I think the electric choke was the worse part. But Holley makes the best carburetor, right?

One day about 9 months later, the Holley developed a slow leak at one of the fuel bowls. Feeling defeated, I began to regret my decision of ever converting to a 4-barrel carburetor to begin with. I never seemed to have any of these issues with my original Motorcraft 2150. "If only Ford made a 4-barrel version of the original Motorcraft 2150" I thought. So after a bit a researching, I found that Ford *did* make a 4-barrel version of my original Motorcraft 2150 (which started out as the Autolite 2100) in the form of the Autolite 4100. But Ford stopped making them in 1968, and there were MANY different calibrations over the years. And they could be costly, because the Mustang guys want these for their restorations. Undeterred, I managed to find one designed for a 289 Windsor engine with an automatic transmission with the exact same bowl size (1.08) as my original 2150!

I paid about double what my brand-new Holley carburetor cost me, but I have been satisfied ever since. Like you, my fuel mileage was quite a bit better with this old Autolite 4100 than it ever was with the Holley. My idle speed is set to 600 RPM and it returns there no matter what. And the thermostatic hot air choke works flawlessly. And most of this is because the Autolite 4100 I have was specifically designed for my engine, whereas the aftermarket Holley is a "universal" style carburetor. I can honestly say that I can't tell much difference between driving Lucille and any of my other vehicles with EFI. And I haven't had to touch the carburetor in years!

[Jake Papageorge]

Thank you for this anaylsis. I really enjoyed reading that!

The results are just what I expected. So many people are quick to dismiss the Motorcraft [Holley] 4180 as an "emissions" carburetor that should be replaced. Yes, it is that - but the 4180 is also one of the most *precise* carburetors Ford ever built. The primaries have annular boosters, which atomize fuel almost as well as fuel injection. The 2-stage power valve is much more precise than a standard single stage. (I am actually surprised you manged to find one.) And like you said, the choke system found on the 4180 is far superior to any other found on aftermarket carburetors. Ford engineers knew what they were doing when they designed these. There is actually much more engineering with the stock carburetors than most people realize. Ford engineers took into account engine type, engine size, transmission type, emissions, and even vehicle weight when they designed each carburetor for their application. They may look the same on the outside, but these carburetors can be much different internally.

I strongly considered running a Motorcraft 4180 from a Mustang GT when I replaced the original feedback Motorcraft 2150 on Lucille. Against my better judgment, I decided on a brand-new Holley Street Avenger instead. It ran okay, but I never could seem to get it tuned just right. And it seemed to constantly need to be fiddled with. I think the electric choke was the worse part. But Holley makes the best carburetor, right?

One day about 9 months later, the Holley developed a slow leak at one of the fuel bowls. Feeling defeated, I began to regret my decision of ever converting to a 4-barrel carburetor to begin with. I never seemed to have any of these issues with my original Motorcraft 2150. "If only Ford made a 4-barrel version of the original Motorcraft 2150" I thought. So after a bit a researching, I found that Ford *did* make a 4-barrel version of my original Motorcraft 2150 (which started out as the Autolite 2100) in the form of the Autolite 4100. But Ford stopped making them in 1968, and there were MANY different calibrations over the years. And they could be costly, because the Mustang guys want these for their restorations. Undeterred, I managed to find one designed for a 289 Windsor engine with an automatic transmission with the exact same bowl size (1.08) as my original 2150!

I paid about double what my brand-new Holley carburetor cost me, but I have been satisfied ever since. Like you, my fuel mileage was quite a bit better with this old Autolite 4100 than it ever was with the Holley. My idle speed is set to 600 RPM and it returns there no matter what. And the thermostatic hot air choke works flawlessly. And most of this is because the Autolite 4100 I have was specifically designed for my engine, whereas the aftermarket Holley is a "universal" style carburetor. I can honestly say that I can't tell much difference between driving Lucille and any of my other vehicles with EFI. And I haven't had to touch the carburetor in years!

Man, you said a mouthful!

I remember many years ago when I worked a high school job at Kirks Carburetor in Detroit and let me tell ya, the core room in the place had every single carburetor in the world in there! In the first week, I pulled out a old Holley 3 barrel, a host of other 4150's, some of which I still have! The one carburetor I never pulled out of that core room was the 4180. Everyone else in the place loved those carbs, but after several tries, I just could never get it working right. Years later, I started working these carb's for guy's with Mustang GT's at the dealership, and on the the F150's (I was the drivability guy for about 4 months) and once I got them figured out, I was pretty impressed with them. They had a lot more adjustments than a typical 4150 (which I was accustomed to) and the parts were just a hassle to get!

Now, here I am bringing one back to life on my own truck. Funny how that works out! I have this thing working great, I finally got the EGR up on this thing so I am going to start my mileage test tomorrow. BUT WOULDNT YOU KNOW IT...........

The welch plug on the primary float bowel is sweating fuel! LOL!!!! I must have throw away a thousand of those float bowels over the years and now, I just had to go buy one off of Ebay. Fortunately, I have extra bowl gaskets in stock, but I could just stick my head in a wood chipper for not hanging on to at least ONE damn core! This stuff is starting to get very hard to find.

BTW....I totally agree with you on the "precision" of this carburetor. A lot of people have no idea what kind of benefit the combination of the 2 stage PV with Annular boosters can provide mileage and responsiveness wise. The choke set up, once adjusted properly, is really one of the carburetors best features. It is just getting there that is the thrill ride! LOL!!!! Also, this carburetor was my first experience with "close tolerance" jets. Now, that's all I use. I use the 2's in the street cars and the 3's in the race cars.

I also agree totally on the street avenger and would only add that no matter how well you jet it, set the floats, whatever....those carburetors run rich! I guess if the 4180 is a fine point mechanical pencil, the street avenger is more like a big fat highlighting marker! That street avenger and the quick-fuel equivalent are just cheap, die cast knock-offs with very sloppy metering characteristics! You get your hands on an old school 1650-1 and if you can live with a choke that will never work right, those were far better carburetors than the street avengers are.

[Rembrant]

Great read! I love it when people take the time to do comparisons like this. Well done.

I know Holley is one of those love 'em or hate 'em brands, and I know a lot of people say that the 4160 runs rich right out of the box, but when I had my newly built 302 on the dyno with a 4160, we had to bump the stock #66 jets up to #68 as it was actually running just a little lean throughout the range, and definitely lean on in the upper RPM's. I may be totally wrong in asking this, but with the results I had on the dyno, I have to wonder how could a 4160 ever run rich on a larger displacement engine? I expect the higher flowing GT40 heads had a lot to do with my results, so the same heads on a 351W would presumably have the same results. Anyway...it's more like a wide open and curious question, since I'm far from any kind of a carb expert lol...heck, I don't even like carbs that much lol.

When you said that this comparison was NOT scientific, I said to myself this guy needs to install an AFR gauge!! Then I read a few replies down, and you are getting one. That's a must for this type of testing...that gives you an actual measurement.

But I'm at about 13 with my heavy 4wd F250 and a 460/ZF5 combo, so it is possible to do better than 12. And the 400 in Dad's truck should easily do 14 or more with the E4OD. So it can be done.

Gary, out of curiosity, how much of that 13MPG do you attribute to the 5spd w/OD? It has to be significant, right? Your truck would probably be at more like 10MPG with a 1:1 final drive?

I'm a big believer and proponent of installing an overdrive transmission in these trucks. To me it's almost a necessity if you're going to use it any amount, and with the price of fuel these days, it makes more sense then ever.

I got 15MPG with my little '84 F150 with relative ease (4160 on a 302 that dyno'd at 300HP). However, that's a 3400 lb 2wd truck with a 5spd swapped in which allowed me to run at 1900RPM on the highway. I was able to get it up to 17 and 18MPG a couple times, but that was burning a whole tank on the highway at 60-62MPH with semis and little old ladies passing me (it takes concentration to drive THAT slow in a truck that wants to drive fast lol). Regular driving though, it was usually in the 15.5MPG range, which I thought was decent all things considered.

With the new 302 I built now (basically stock, but bored 0.040 over), I'm going with the new version of that 4100 carb Rick was talking about above: The Summit 500 CFM 4bbl with the annular boosters, etc. That with an AODE-W behind it, and a 3.55 geared rear end. It will work better than my '84 did with the OD and 3.08 diff, but how the MPG turns out is yet to be determined lol.

In any case, great job Jake, and please keep us posted on further results. I think an AFR gauge is in order here! I would much rather have a 351w over a 302, but 302's are so much easier to come by.

 

[Gary Lewis]

Great read! I love it when people take the time to do comparisons like this. Well done.

I know Holley is one of those love 'em or hate 'em brands, and I know a lot of people say that the 4160 runs rich right out of the box, but when I had my newly built 302 on the dyno with a 4160, we had to bump the stock #66 jets up to #68 as it was actually running just a little lean throughout the range, and definitely lean on in the upper RPM's. I may be totally wrong in asking this, but with the results I had on the dyno, I have to wonder how could a 4160 ever run rich on a larger displacement engine? I expect the higher flowing GT40 heads had a lot to do with my results, so the same heads on a 351W would presumably have the same results. Anyway...it's more like a wide open and curious question, since I'm far from any kind of a carb expert lol...heck, I don't even like carbs that much lol.

When you said that this comparison was NOT scientific, I said to myself this guy needs to install an AFR gauge!! Then I read a few replies down, and you are getting one. That's a must for this type of testing...that gives you an actual measurement.

But I'm at about 13 with my heavy 4wd F250 and a 460/ZF5 combo, so it is possible to do better than 12. And the 400 in Dad's truck should easily do 14 or more with the E4OD. So it can be done.

Gary, out of curiosity, how much of that 13MPG do you attribute to the 5spd w/OD? It has to be significant, right? Your truck would probably be at more like 10MPG with a 1:1 final drive?

I'm a big believer and proponent of installing an overdrive transmission in these trucks. To me it's almost a necessity if you're going to use it any amount, and with the price of fuel these days, it makes more sense then ever.

I got 15MPG with my little '84 F150 with relative ease (4160 on a 302 that dyno'd at 300HP). However, that's a 3400 lb 2wd truck with a 5spd swapped in which allowed me to run at 1900RPM on the highway. I was able to get it up to 17 and 18MPG a couple times, but that was burning a whole tank on the highway at 60-62MPH with semis and little old ladies passing me (it takes concentration to drive THAT slow in a truck that wants to drive fast lol). Regular driving though, it was usually in the 15.5MPG range, which I thought was decent all things considered.

With the new 302 I built now (basically stock, but bored 0.040 over), I'm going with the new version of that 4100 carb Rick was talking about above: The Summit 500 CFM 4bbl with the annular boosters, etc. That with an AODE-W behind it, and a 3.55 geared rear end. It will work better than my '84 did with the OD and 3.08 diff, but how the MPG turns out is yet to be determined lol.

In any case, great job Jake, and please keep us posted on further results. I think an AFR gauge is in order here! I would much rather have a 351w over a 302, but 302's are so much easier to come by.

Cory - I don't have a good baseline to answer your question as I made multiple changes at the same time, going from a worn out 460 with a 4-speed to a new Scotty-built 460 with a 5-speed with OD. But let me go back over my posts:

• 10.6 to 11.3 MPG with the worn-out engine and 4-speed

• 11 to 12 MPG with a new engine and the ZF5, but running a carb

• 12.6 to 13.6 MPG with the new engine, ZF5, and EFI

So how much of the +1 MPG to give to the ZF5 vs the different engine vs the OD? I don't know. But it is pretty easy to see that the EFI added 1.5 MPG on top of that.