Memorial weekend trip.....630 miles..... 8mpg!!! and 74 gallons (UPDATE)

[Susan76]

not the only one

Took my 76 soft top for a 230 mile run on Sunday. First real trip since 10 months of mods & upgrades. 8.9 mpg with 302 C4 4.11 locker, BFG 12.5 33s, Rancho 3" (I think) performer intake, Holley Truck 470, 14* initial advance with total in by 2,400 rpm (sorry don't remember total but it was ok), mid length 4 into 1 headers (don't know the brand) into duals without a balance tube. Speeds by GPS and mileage corrected for 7% overspeed on the speedo. Trip was 90% freeway varied from 55 (construction) to about 70. 10 miles city and the rest country roads. Most of the time I held it at 60-65. About 2,800 rpm @62mph. Vacuum @ 10-11" most of the time. Water temp @ 200*. Air filter is a 14x4 1/2" open element. Rear window out and door windows down. REALLY disappointed....http://classicbroncos.com/forums/imagesCB/smilies/cry.gif

Thinking of throwing in a set of 3.54s that I think are on the shelf just to drop the rpm as an experiment. Low range 1st gear final should still be 17.6 vs 20.5. Should drop highway rpm to about 2,400. Also makes me want to jump on my 69 Ranchero so I can have the 351W out of it for the Bronco. Torque being the answer to pushing a brick through the air.

 

[half cab]

If I get past 60mph with this old carbed 351W you can almost watch the fuel needle moving towards yonder closer to mty.

 

[bmc69]

If I get past 60mph with this old carbed 351W you can almost watch the fuel needle moving towards yonder closer to mty.

I get exactly 10 mpg at 55 in my old trail rig with the EFI 408C. If I push that thing to 65...the mileage drops to less than 8.. So I just don't.

 

[Revelation]

Bronco aerodynamics are as good as a

 

[77-302]

Ok guys,
Little update for you.
First step pulled out my old stock carb.
.048 jets
Opened up the one I got from my buddy ( currently on the truck) .057's!!!!
Think that might be a significant source?!?! I do...
I swapped them out. Fired it up and she seems happy.
I'll take it for a test run later this week�� to see if she responds differently.

 

[englewoodcowboy]

Memorial weekend trip.....630 miles..... 8mpg!!! and 74 gallons of 89 octane....

That is a 16% reduction in jet size or increase depending how you look at it. What color were your plugs? I would guess them to be dark. Curious for what you discover. I wouldn't expect a whole lot of increase but I would expect to see an improvement either way.

 

[77-302]

That is a 16% reduction in jet size or increase depending how you look at it. What color were your plugs? I would guess them to be dark. Curious for what you discover. I wouldn't expect a whole lot of increase but I would expect to see an improvement either way.

Yes sir on those %'s.
I'll pull plugs after kiddo's go to bed.
I'll snap some pictures too.

In other news I talked to the guys at Howell Injection.
$1350 for the universal kit with heated O2 sensor.
I might be able to save some money if I go to pick and pull to get a TB and computer and bring it to them since they are about 1.5 hours away...We'll see...

 

[70_Steve]

Also makes me want to jump on my 69 Ranchero so I can have the 351W out of it for the Bronco. Torque being the answer to pushing a brick through the air.

Mild build EFI 351 with an NV4500 (.73 OD), 4.56 gears and 35's. The one time I checked mileage using a GPS I averaged right around 15 mpg on the highway.

 

[Pa PITT]

... Sorry I Didn't get all the reply's read.. But most of them.. I Say your just about on on the Mileage for your 302. I never had one get that.
.. If I get a vote, then I vote for MUSTANG or Exploder EFI & THE 4R70W OD ..TRANS
... Don't use the AOD trans my Running Buddy did this one.. He finally had to go to the Ford DealerShip to get it fixed. overhaul cost about 2500. end result.. No One else remembered how to build them.

 

[Viperwolf1]

Speeds by GPS and mileage corrected for 7% overspeed on the speedo.

The error of the speedo will not be the same as the error of the odometer. They are 2 independent devices that run off the same cable. Test it against some mile markers and you'll see.

 

[mlogan24]

Yes sir on those %'s.
I'll pull plugs after kiddo's go to bed.
I'll snap some pictures too.

In other news I talked to the guys at Howell Injection.
$1350 for the universal kit with heated O2 sensor.
I might be able to save some money if I go to pick and pull to get a TB and computer and bring it to them since they are about 1.5 hours away...We'll see...

$1,350?! If you're contemplating spending that much, I would at least make a little effort to score a junkyard 5.0 EFI setup. In my mind, even a speed density setup is much better than a TBI swap.

Speaking of speed density, you should be able to score one of those for cheap bucks.

 

[broncnaz]

Jetting cant always just be swapped over to another carb most likely the carb off the 351 is larger it needs larger jets to provide the correct fuel for the added air. Thats not saying you dont need smaller jets its just that you may not have enough jetting now and You really should have checked the spark plugs before just swapping jets. It wouldnt be a good thing to lean out your new engine. Also your engine is probably not even broken in yet. Friction is still high which robs power.
Along the lines of a bigger carb bigger is not always better in the mileage game. Especailly with 2v carbs. Bigger is good at the track but thats about it. Id consider putting your stock carb back on.

A few other things. While 33in tires and 3.50 gears are not the best you should be fine running it down the hiway. You should also get better mileage than what your getting. For the most part A correctly tuned engine will get you as much mileage as a EFI setup. Its just you actually have to tune it vs the EFI doing the tuning. Plus tuning is pretty cheap compared to swapping EFI, transmissions, axle gearing.
You probably need to back that timing off a little check the plugs, get a vacuum gauge to get readings while your cruising down the road. You really want to adjust the timing so you get as high of vacuum as you can while crusing. That keeps the power valve from opening at cruise. Also you can find out what your running at and change the power valve if needed.
The 2.5in dual exhuast may be hurting you a little as well. Would go no bigger than 2 1/4" on a stock 302
Ive never been sold on the howell EFI if you needed EFI for offroading then it works but if you plan on EFI hit your pick and pull and get the stock ford stuff its better than any TBI setup and will probably cost you less.
Also your C4 may be slipping and eating up some of your mileage.

 

[wildbill]

You need 4:11 gears Bill ;D

 

[Rox Crusher]

If your going to use this ol girl for long road trips then I would either tune the current engine and switch to 4:11 gears or go with Explorer EFI with 4R70W and 4:88 gears.

If you go with the Explorer EFI set up use the OBDII harness set up from EFI Guy on this site as it will eliminate the need for 600 dollar transmission controller.

I did an Explorer EFI and 4R70W a couple years ago and loved it but my 3:54 gearing made the OD useless at hiway speeds.

I just swapped to 4:88 gears and love them as they put the motor in the right RPM range at 70 mph. The added benefit for me is the low gearing in first gear which allows me to go wheeling without having to be on the brake all the time. Totally Awesome !

Get out the wallet and the wrenches !

 

[77-302]

$1,350?! If you're contemplating spending that much, I would at least make a little effort to score a junkyard 5.0 EFI setup. In my mind, even a speed density setup is much better than a TBI swap.

Speaking of speed density, you should be able to score one of those for cheap bucks.

Carb is the same (2150) with same venturi size so swapping jets was the only unique part between the two.

I would love to do a Ford EFI swap.
And while I consider my self a pretty competent mechanic as I've hand build several engines, the Ford EFI swap still seems like a mystery to me. As long as I've been on this site it seems that there isn't straight forward installation laid out step by step for how its done. From what to get from the junk yard (Keep this, pitch that) to modifying the lower intake, to which ports to plug, to which wires to connect to what computer to use.... I get that you want MAF vs Speed density. What about fuel pumps, fuel lines, keeping the stock hood, keeping the stock tanks, rearanging the location of the overflow tank or duraspark module... Impossible no... time consuming yes.... If I have to pay $500 more for a plug and play system I'll do it just so that it gets me back on the road sooner. It sounds like if I did the Ford EFI set up I'd be down for 6 months tracking down parts and trouble shooting issues... IMHO...Maybe a good winter project but like the rest of you who are driving these old girls the list of wants grows faster than the bank account... Door seals, door hinges, stereo, wire harness, body mounts, POR frame, strip and repaint body, strip and repaint top, interior carpet and sound deadener, etc etc... So I have to weigh the time I have and the money I have vs what I'm willing to give to this old girl... for now I'll keep enjoying it and try to be patient... Prioritize the items which make it fun to drive and take to shows.

 

[WheelHorse]

Ok guys,
Little update for you.
First step pulled out my old stock carb.
.048 jets
Opened up the one I got from my buddy ( currently on the truck) .057's!!!!
Think that might be a significant source?!?! I do...
I swapped them out. Fired it up and she seems happy.
I'll take it for a test run later this week�� to see if she responds differently.

If you look back through my 2150 carb tuning, you'll see where I had 57's in my 2bbl and the afr going down the road was in the 11's. Dialing in a 2150 via wideband

52's put me around stoi.

Disclaimer, this is on a 1.08 venturi carb, not a 1.21. Results should be measured via wideband.

This is why it is important to run a wideband, even on a carbed rig. I can tell you that SOTP's can't tell a damn bit of difference between 17.5 and 11.1 other than a slight hesitation upon take off.

Most guys put carbs down when they switch to FI because they never truly measured where they were at prior to making the switch. So they go from way lean or rich areas to computer adjusted and now it's so much better. The unfortunate part is if they had logged the carb manually and made the appropriate corrections the same way way the comp does it, they'd see similar performance.

PS, if you were closer, we'd weld in a bung and just hook mine up, dial it in and send you on your way. However, You'd spend more on gas then just buying the sensor yourself.

 

[MPG_Bronco]

http://www.affordable-fuel-injection.com/ixxocart/catalog/Ford-13-1.html

I went this route on my 65 mustang i6, did a 2bbl TBI from them. got it up and running in less than 1 week. their harness has EVERYthing you need, even electric fan control. all using stock parts that you can ask for at the counter.

they use a 3 wire o2 sensor, and getting a program to read the computer to your laptop is convenient.

All i needed to add to the kit was some aluminum gas pipe for feeding it, used the original for the return. worked great!

I also had an HEI DUI for my 200ci, that was swapped over for the computer to control. all tuning went away. for the 200 the TBI was big so a restrictor plate under the tbi helped keep the CFM down and the throttle response great.

if I got bought a bronco with a carb, this is most def what I would do again. best investment on the mustang.

 

[77-302]

If you look back through my 2150 carb tuning, you'll see where I had 57's in my 2bbl and the afr going down the road was in the 11's. Dialing in a 2150 via wideband

52's put me around stoi.

This is why it is important to run a wideband, even on a carbed rig. I can tell you that SOTP's can't tell a damn bit of difference between 17.5 and 11.1 other than a slight hesitation upon take off.

Most guys put carbs down when they switch to FI because they never truly measured where they were at prior to making the switch. So they go from way lean or rich areas to computer adjusted and now it's so much better. The unfortunate part is if they had logged the carb manually and made the appropriate corrections the same way way the comp does it, they'd see similar performance.

I like you way of thinking as I like seeing real data vs SOTP...I have a wide band A/F meter on my mustang. Problem with my Bronco is that I don't even have a bung location in my long tube headers. In theory I could move the gauge temporarily over to my Bronco if I did. Problem is that gauge and the sensor are about $450 if I remember correctly. Might be better playing with a vaccum gauge at first.

 

[Derekryan84]

I cruised at 70 and got 8mpg with a stout 351w. 4.11s c6 35" tires 2500rpm. Going to put some 37's and see if that helps mine any.

 

[broncnaz]

Wide band is a fine tool. Vacuum gauges work too. With experiance you can tune a carb without wide band people did it and have done it for years before there was even a wide band in the picture. They cant have gotten it wrong all those years even after EFI came on the scene as carbs were still king of the track until recently. Of course carbs are still prevailent at the track although Im sure they are using wideband monitioring in some cases.
Since both your carbs were the same size then you should be ok and probably closer to your needed jetting although with your engine mods you may need to step the jetting up slightly. but then again you may not.