OH NO! ANOTHER MILEAGE POST!!!!

Well damn it. Here I sit, pondering ANOTHER engine build, with an emphasis on mileage! What happened to the hot rodder in me? did it choke and die?

Ok Seriously....

Considering the out of pocket cost for trading my Focus in, I've decided that putting the money into one of my other vehicles would better suit my needs.

Aside from the Focus, most of you know I own the Mustang, the $100 Galaxie, and my 79 Bronco. The mustang is out of the question, as 2 car seats in that car isnt really concievable. The Galaxie would fit the bill nicely, except it needs everything! This leaves the Bronco.

The Bronco looks good, the interior is a well taken care of original, and is also pretty roomy. All it needs is drivetrain issues reseolved. Currently the engine is a well worn 460 smogger engine, with hacked accessory brackets to boot. It is backed by a C-6 and an NP205 Case.

Plans for the Bronco include removing the entire eng/trans combo and replacing it with a small block/manual trans set up.

The first part of it is done, as I have already installed the clutch pedal and associated parts. I've got most everything to finish the swap, including a 351w roller motor from a 94 F-150.

I was planning on dropping it in stock, but since Im not planning on dumping a few thou to trade the focus off, I figured I could put it into the bronco.

Now everyone knows, the key to mileage is an abundance of low RPM part throttle torque. So lets build a stroker.

Here is my current plan, if anyone would have any suggestions that could suit my needs even better, please say so.

393 shortblock
GT40 heads (gasket matched, possibly mild ported, but want to keep velocity up)
CC266HR roller cam
Edel performer RPM intake
Tube headers (unsure of exact set as a 351w in a 79 bronco isnt exactly a factory setup)
Carter 625 carb
Duraspark ignition

It is my belief that if I can build a substantial amount of torque, seeing 13-15 city out of this engine should not be hard. Comments or suggestions?

[addsig]

Definately take advantage of the available EFI components for this engine to help you achieve maximum fuel efficiency and throttle response.

_________________
1975 Elite - 460 powered, tire shredding, daily driven project car.
1985 Bronco II - Cammed-up, bored-out, snarling 2.8-powered 4x4 toy.


<font size=-1>[ This Message was edited by: RyanJ on 10/16/05 7:16am ]</font>

the key to mileage is keeping rpm's down. My mustang with a very healthy 302 gets 20 mpg on the freeway because of an overdrive. So I suggest a T-5 tranny as a huge part of economy. Also a cold air induction kit and a multiple spark box will help milage too. Also your exaust should be free flowing but have enough backpressure to keep the torque.

Fuel injection is not an option for me, I dont much care for it on older vehicles. Too much headache IMHO.

As for the T-5, this is a 79 Bronco 4x4. T-5 is not a possibility. I will be running a manual transmission, though not an overdrive. The gears will be 3.50s, and the tires a minimum of 33 inches tall.
[addsig]

I think the stock EFI system would be much better for mileage and low-end torque because of the very long runners... but you've already said a big fat NO to the EFI and frankly I don't really blame ya [img]/phpBB/images/smiles/icon_lol.gif[/img].

That being said, however, I think it's physically impossible to get better than 15mpg (highway) out of a Bronco [img]/phpBB/images/smiles/icon_lol.gif[/img], regardless of the engine. I think even the EFI 5.0 Broncos were rated around 16mpg highway and I dunno if anyone ever got that. The best my Bronco has ever gotten is about 12mpg highway and that's with a very mild 460 with gobs of low-end torque and roughly the same final-drive ratio as what you're going for. So I think 13-15 city is a little optomistic to say the least, but I'd love for you to prove me wrong [img]/phpBB/images/smiles/icon_wink.gif[/img]
I don't think the stroker is gonna be the best for mileage... at any given RPM you'll have both more frictional loss and more pumping loss with the larger engine. Engines are most efficient at low RPM (less frictional loss) and under heavy load (less pumping loss due to intake vacuum, and greater cylinder filling leads to higher dynamic compression ratio and more complete burn). However I don't know how much mileage you'll loose by going with the stroker... if it's only 1mpg it would probably be worth it to have the extra torque on tap for pulling a hill or the occasional headwind. Also if mileage and low end torque are your main concern you might be better off with a regular Performer intake. I'm not sure how they perform on the 351s, but from what I've seen the Performer 460 out powers the Performer RPM everywhere below 3000rpm. And lastly, I'd consider using a quadrajet carb. They are supposed to get much better mileage than a Holley or Edelbrock, and so far I've had good results with mine on my Bronco (although I haven't taken it out on the highway to see how much better it REALLY is). You'd have to use an adapter plate though, so that might not be the most appealing option for you.

_________________
'86 Bronco fullsize, 460, E4OD
'85 Ranger, 340hp 289, T5


<font size=-1>[ This Message was edited by: Motorhead on 10/16/05 9:36am ]</font>

I agree that a quadrajet will probibly give better milage. Big (heavy) tires will kill your mileage however. The 4wd does not help either. My truck (chevy 3/4 ton) with a 454 (quadrajet), manual trans, 33 inch tires, two wheel drive, and 3.73 gears gets about 6 mpg. But on the otherhand it will tow tree stumps out of the ground all day long. 15 mpg sounds a little optimistic to me.

I managed to get 12-13 city and 14-15 hwy out of my old 74 F-350. At one point I managed 12 loaded to 9000-9500 lbs, doing 85+ all the way to Rifle, CO and back. I know I can get close to this.

The F-350 weighed in at 5500 lbs. I was running 4.11 gears with 33 inch tires, but I had an OD transmission. This was with a Holley 750 carb, and a truck that was CONSTANTLY in need of an alignment.

My goal is to simply get as close to the torque curve of that 460 as possible, while saving weight with the small block while Im at it.

I never said my goals were absolute, but givin my prior history, I think I can get pretty close to it.
[addsig]

If your looking for mileage, I would look into getting a ZF S5 42 or ZF S5 47. There the 5 speed that came in the 87-95 f250 and f350. they have a 5.72 first and 0.76 fifth gearing.

http://www.zf-group.com/am/pc/lt/ampclt03.phtml
http://classicbroncos.com/ZF_Transmission_Swap.shtml
http://www.cardomain.com/ride/315211/6

_________________


<font size=-1>[ This Message was edited by: 66Fairlane on 10/16/05 11:37am ]</font>

<TABLE BORDER=0 ALIGN=CENTER WIDTH=85%><TR><TD><font size=-1>Quote:</font><HR></TD></TR><TR><TD><FONT SIZE=-1><BLOCKQUOTE>
On 2005-10-15 22:48, Luv70sFords wrote:
I managed to get 12-13 city and 14-15 hwy out of my old 74 F-350. At one point I managed 12 loaded to 9000-9500 lbs, doing 85+ all the way to Rifle, CO and back. I know I can get close to this.
</BLOCKQUOTE></FONT></TD></TR><TR><TD><HR></TD></TR></TABLE>

Wow, that's impressive! Towing my Ranger back from Portland I got 9mpg on the way there with an empty car trailer and 9mpg on the way back with a 3000lb pickup on the trailer. Seems like that's the way big-blocks work though... the mileage is bad, but doesn't get any worse when you load it down. I think your build look like about the best a person could do keeping mileage in mind, so who knows maybe you'll prove me wrong [img]/phpBB/images/smiles/icon_wink.gif[/img].
[addsig]

About the only thing not mileage minded about the build is the intake. A regular performer would likely be a bit better, but Im hoping the added cubes of the stroker will help to offset the increase in runner volume from the RPM manifold and keep velocity up. Mainly because I already have the intake [img]/phpBB/images/smiles/icon_smile.gif[/img]

I am a cheap SOB afterall...

Regarding the 460, it was pretty darn close to stock, which is a very big part of why the mileage was so great. Stock intake, small CC268H cam, and a nice set of headers flowing into a single 3 inch pipe. I built it for torque for the truck, and boy I got it. Im hoping the lighter weight of the small block combined with the overall lighter constuction of most of the bronco will help offset the weight of the front axle and transfercase.

I actually considered rebuilding the 460 that is has currently and swapping it over to a manual, in order to get the mileage I previously got in the old F-350. But I dont really have many of the parts I would need. And I really dont like using aftermarket mounts either. Oh and headers.... Forget about it $$$$$. Im thinking if nothing else I can likely get away with a set of stock Lightning headers in the Bronco.

Im trying to balance the cost of the engine along with the intended overall use of the truck (daily driver, offroad toy, and hunting rig) and to of course to not go overboard building the truck, because the less moeny I spend, the more gas I can buy.

I have toyed around with various OD unit ideas, but unless I stumble across a deal, I cant do it. The ZF route is expensive mostly do to demand. Clark 5 speeds are hard to find, and along with the NV4550, require changes in the clutch, and possible even the bellhousing. Advance adapters makes a REAL nice OD unit that bolts between the tranny and the bellhousing, but in the short wheelbase of the Bronco, it starts wreaking havoc on the driveline angles pretty quick.
[addsig]