I recently picked up an '85 airporter bus body on an E350 dually with a big brite 460 in it.--Got it on Ebay in phoenix,worked some bugs out,drove home (1400 miles) pulling a load........hardly used oil purrs like a rhino.-------I'm wondering what the most effective ways to stretch mileage ,as I just don't need all the power!.......................cheers!!!

 

My answers are generic since I haven't done this with a carbed 460. My experience with modding engines comes from 60s era Dodge Wedges.

Maybe higher ratio(lower number) gears. I think most of those buses had pretty low(high number) gears, just SWAG.

An RV cam and a good spread bore carb(a guess would be about 750cfm with vacuum secondaries). Maybe the Offenhauser(Not sure if they still make this) dual port manifold. The dual port has tiny primaries that give excellent(relatively speaking) fuel economy running off small primaries on the carb. Then when you need power the secondaries on the carb pump thru the big secondary ports on the manifold.

Maybe a better ignition system, not sure what brand I would recommend for that year.

A good flowing small tube exhaust system. Big tubes are for high RPM power, small tubes give low RPM response which means fuel efficiency for your purposes.

Hope some one with actual experience with this year steps in. Like I said my recommendations are generic in nature.

Good Luck,

Jim Henderson

 

Jim,thanks for your response!!.....now that I've had a chance to look around this section,I've found lots of hints,but can tell that really you have to put in lotsa $ for relitevely minor changes.

I get about 10mpg at present--if I modified everything to the max,what could I hope for??...at what budget??

Gear ratio....how do I tell what I've got??How pricey to change it??............would tire size be a simple way to adjust relative gear ratio?-or over simplifying??--I've got 215's on,if I throw on 235's would it be a good mileage stretcher??

I'm curious about -Ignition system--what type of changes produce what results??

Is there anything to be gained in tweaking the timing??

What's the best cam/carb combo(and budget?) for these purposes??
........................cheers!

 

750 is too big for a 460 unless it's had major porting done to the heads and manifolds. 650 CFM is actually just right.

10 MPG in a airporter van? There are people running pickups that don't get that!

Good suggestion about the RV cam. What carb is on it now? The Autolite 2V is a good mileage carb, and likely what it has.

You change the gear ratio by changing the "pumpkin" in the rear end. Very easy to do with the Ford 9 inch.

 

A E350 dually would not have a 9 inch rear end.

 

...the bus has a holley carb of some sort.Mechanically,this bus turned out to have been very nicely maintained,though the electrics were terrible!!--ended up having an engine fire once I got home.--just got the thing running again ...................... relating to this,how do I tell if the vacuum assist on the brake master cyl still works?--I suck on the hose and seem to get some resistance--good enough??

What's the best way to identify the rear end and gearing??...........and again,would larger tires accomplish the same?,or oversimplification?What I like of this idea is the ease of changing back when I've got a load to pull.---make sense??

 

If you are getting 10 mpg I don't think I would mess with it. 12 is the best I have seen on a stock 460 (some folks will argue that) My 89 f-super duty (one level above f-350) gets 8 mpg and it gets that empty or with 5 tons on it.

 

460s in cars can easily get 16 MPG. It's not the engine, it's the application.

 

460s can be made very efficient, you just have to pick the right parts.

Heads - ditch the late model 95cc heads. They are great for reliability and low emissions, but terrible for efficient combustion.

Timing - toss the late model retarded timing set (pun intended) and get a set spec'd for pre '71 applications.

Compression - bump the compression to around 9.5:1. As with the heads, the stock compression is great for reliabilitya and emissions, but kills combustion efficiency.

Cam - Ditto what I said for the heads and compression ratio above. There are several really good cams out there that will maximize mid-range efficiency. This will boost overall torque significantly, while providing better fuel economy.

Intake - a good dual plane intake like the Weiand Stealth, Edelbrock Performer or Offy Equa-Flow will always be a smart choice.

Carb - size matters. A monster carb looks good and makes for great bench racing, but you want a relatively smaller carb to maximize intake velocity. Something in the 600-650 cfm range will not choke the top-end on a mild engine, and will pick you up some torque and throttle response down low.

Exhaust - monster header tubes are great if you intend to race pro-stock. In a mild motor they cost you low end because they miniize low-rpm cylinder scavenging. Primaries in the the 1-3/4 to 1-7/8 inch range will make the most of mild cams meant to run modest rpm.

Tranny - overdrive is good. A motor built around the above specs, combined with an overdive gear (auto or manual) will maximize your economy and still allow you to run relatively aggressive rear gearing.

Hope this helps!
Brad

 

Yep the cars got 16 mpg with 2:26 rear end gears. Most trucks have 3:55 - 4:10 gears. Which makes 10-12 mpg about right. My super-duty has a Dana 80 in it with 4:65 gears and weights 9000lbs empty. It will pull anything you can get a hold of but it ain't going to get any mileage. Also The timing gears on the 87 and up factory 460's are straight up. I rebuilt mine with the performance options listed above except the heads I just ported and polished mine. I used the hp-535 piston and the Crane 260 cam. The bottom line is at 65 mph in 5th gear (overdrive) iam turning 2800 rpm the cars turn about 1800 rpm

 

Brad...thanks a lot for the information!
What specifically do you suggest for timing equiptment?--Would it make any sense to just improve that area for now??....thanks!!

 

ok, just one question, how do you go about bumping up the compression ratio?

i got an 84 460-all stock except for the exhaust and i was just curious how you do that.... i understand everything else

 

oh yeah, one more question, what is my ratio now.... 8 - 8.5:1?

 

Grease monkey - get a timing chain set spec'd for pre '71 engines. Timing chains are relatively cheap and easy to install. Good headers and a well thought out exhaust system would be next on the list.

BLaCkSiLo - no way to bump compression short of major engine work. The info above was presuming that you were rebuilding the engine. Late model truck 460s were 8:1. It sucks for efficiency, but it makes for great reliability (not to mention the fact that it makes the 460 supercharger-friendly).

Brad

 

Brad..everyone....thanks for clearing that up!-the engine I got with that old bus is very tight ,and virtually as new,so no need to open it up for now.---Is there something external I can do beyond tuning carb and dist. timing??------Anything I can do to optimize the distributor electronics for now?
Otherwise ,I think I'll mess with tire sizes for a bit.
Just finished restoring the thing from an electric fire last summer,so other than optimizing details,I plan to run to Baja soon!!.
p.s....is there a section on this site where I can find expert ford tech shops---the type of guys who I can trust to baby my beast???..................cheers!!!!...mike