raising the compression ratio makes the engine more efficient, hence more hp and more tq via better volumetric efficiency. You can have high compression tow motors, just you don't really need a 400hp big block to tow a 10,000lb trailer around. you could build a 9:1 or 10:1 460 with a small torque cam and you would definitely appreciate the extra 100+hp and 100+tq over your 8.2:1 motor, and all the torque would be right there on the low end off idle for towing and tearings axles up or removing the tread from rear tires, just whats the point? still gotta go the speed limit.... maybe its just who gets there faster huh?

 

Well, yes, it is fun getting there faster but also getting into traffic without getting the person coming up on you mad cause you are slowing them down because you can't get up to speed fast enough, and not having 20 cars piled up behind you when you are going up a steep hill on a two lane road whether towing or not, also yes we must get there faster than the import trucks even the mini pick up, and the sound yeah, and the ...

 

yeah i have a 429 in my truck thats bored 60 over and 9.5:1 compression and and a good cam..i i have it in my 78 F250 and i am getting 8.5 mpg ..in the city on the highway and loaded or unloaded..i have 3.08 gear ratio and i turn about 3000 rpm's at about 70 mph...but i agree with 4 60stroker ..that if you do raise the compression the hp goes up and in relation the torque will go up also ...and with this engine the torque is there and plenty of it...even with the 3.08 it still pulls really hard off take off ..but thats my two cents take it easy

 

I have '87 F350 Crew Cab 4x4, ZF 5 speed, 3.55 front n rear, 265/75/16 firestones, 460 bored .40 over with approx 9:1 comp. ratio. hyper pistons, roller rockers, stock 650 cfm carb, stock intake, headman headers, K&N, MSD Coil, Cap and MSD 6 box, dual 2 1/2" exhaust. I think my cam is a Crane 260 or 268H. The engine has about 100,000 and some original parts of the truck have about 420,000. The idle on the carb is rich, otherwize it runs pretty smooth. The truck weighs about 6000 lbs empty. I use synthetic in all but the front end and the engine. The oil pan gasket leaks about a qt/1000.

Here's a couple mileage attainments over the last 2 weeks on trips through western Pa, Ohio and Indiana via Interstate 80. Pa and western Ohio have a few hills.

Last week, loaded with 2800 lbs of short log home logs on the back of the truck, traveling west, between 60 and 72 mph...... 13.38 mpg. Returning from Indiana empty was about 14.4 mpg.

This week, traveling from Central Ohio to Pennsylvania, pulling about 7,000 lbs and loaded with another 1000 lbs, maintaining 65 -75 mph up and down western pa mountains on Rt 80, the mileage dropped to 9.4 mpg. On most hills, 4th gear and 2500 rpms maintained 65 mph and I don't remember having to shift into 3rd gear at any time.

3.55 Gears do ok with loads up to 7000 to 8000 lbs but if I tow over 9 or 10 thousand, I am wishing for 4.10's.


Tony G

 

thx for the info. Tony,

It is great to hear from someone else who is getting closer to 15MPG with a 460 as it seems there is a lack of belief out there when this is stated.

Love all the goodies under the hood and the synthetic lube.

Mine seems to leak everywhere but the engine. I threw a rod so we will see how things do after the rebuild.

Hey take a picture of your truck, I would enjoy seeing it.

 

Yeah, I've been thinking of doing that, but I don't want to break the camera... Seriously, it's not so pretty of a thing to look at unless you appreciate function over form. It's beat up pretty good. I don't know if there is a completely straight body part on the truck... umm maybe the front left fender. But, to my knowledge, the tranny's never been apart, and the rear's not been rebuilt, but otherwise most of the parts have been replaced at least once. The transfer case was just gone through with only a few minor repairs. The front end was even swapped out for a '95 Dana 50 cause someone wanted the Dana 60 that was in it. And it's got a cool MACK bulldog on the front of the hood that sets it apart from the rest. I'll try to get a couple pics and put into my profile.
Tony

 

Ok, I put some pics up in my gallery. Take a peek.
Tony

 

Tony-- looks alot better than mine! Looks good. Thanks for the pics. Thats one of the things I enjoy about this site is seeing everyones truck-- I seem to enjoy the not so perfect truch more than the premos. I esp. like the ones where some guy has done a lot of fixing him self-- I value the hard work.

I keep saying I'll have my engine back in next week but I am still waiting on getting my heads back from the shop. Mine came without a rear bumper and I got pulled over and got a warning for no bumper and no mud flaps. Nice policeman, after the warning in writing he just wanted to know all about the truck.

Thanks again Tony.

Greg

 

To be honest, I have trouble understanding how you can get 15 mpg with 5.13 gears. The exception would be that you stay completely out of the 4 barrel and don't go over 50-55 mph. Then it sounds like the engine would be maybe operating in it's 'happy zone' and be working most efficiently. ??? Just maybe...!!!


Exactly-- I mean exactly correct.
Greg

 

I have a stock 78 460 with the only change being dual exhaust and a eddlebrock 600 cfm . I got 13 mpg 10 yrs ago 200k ago.
Now with it worn out about 300k I get 15 with the addition of a project-the zf 5 speed - cost me about $1000. That was with 3.5 gears doing 65-70 max over a 200 mile stretch all highway w/o any stopping and stock tire size mantaining 1900-2000 rpm's max.
I'm anxious to see what kind of improvement I can get with rebuilt engine and installing straigt up 0 crank gear and removing smog bumps
Been wondering the same as some of yall if increasing compression "improving volumetric efficiency" would give me a mile or more per gallon
later les

 

By playing gear ratio vs. tire circumference (revs/mile actually) it shouldn't be impossible to match them up to a more conventional ratio. Clyde is running 245-75R16's with 3.55's, roughly the (mathematical) equivalent to 235-85R16's with a set of 3.73's.

We ran a lot of 460's where I worked and seemed to see the best solo mileage out of one truck with 235-85R16's and 3.08's but ususally never better than 13-14 mpg ..... of course we weren't making an extreme effort and this truck went through a couple of C6's in it's lifetime.

 

I got 13.5 empty with mine, that is more than I ever expected. 4.10 gears with 235/85R16 at 65 mph

 

Best I've done is 16 with mine, crusing at 55-60, with the secondaries on the holley(factory from a 351W... ran like crap) unhooked, and, again with the new 750 Edelbrock, crusing at the same speed.... I usually average 12-14 though.
Evan

 

yeah 74crwcb probably has his truck running in its sweet spot. either where the engine is making the most torque, has the most vacuem, or at highest volumetric efficiency. man i wish i could get 15 out of my 76 250 its got the 460 but i got 3.73s and 235/85-16's on it i can only pull 11 if im nice but have seen 13

 

Well Greg, I even surprised myself yesterday 10/07. I filled up at the intersection of Plaza rd and Harris Blvd in Charlotte, NC at about 4:15. North on 77 and 81 to Toms Brook, Va where there is a "Loves" truckstop. 342 miles and 6 hours later (at the Love's) I put in 21.622 gallons. This works out to 15.81 mpg. I had stopped at 2 other truck stops for drinks and dinner, but didn't refill. I was traveling between 55 and 75 Most of the time it was about 70 with quite a few hills. The only thing I did recently was to put some msd wires on it replacing Ford Motorsport wires.
TonyG