Hi, I've been lurking and reading trying to figure out what I want to do with my 351m. I recently bought a 77 F150 4x4 w/4 speed. I'll be using it for hunting and towing a small RV. The truck run flawlessly and it's stock configuration has enough power for what I need the truck for.

I understand there isn't much you can do with the 351m unless you convert it to a 400 due to low compression. Is there anything I can do to increase the MPG without replacing the crank and pistons? Maybe a cam swap? Timing?

I don't have the time to pull the engine with having to watch my 9mo old these days. A rebuild will be in in order when he's old enough to entertain himself, or help!

 

A cam swap to a shorter duration, higher lift cam is supposed to give you more power, and by virtue of higher dynamic compression, probably a little better mpg. Only way to know is to do it. First cam up here, read their propaganda. You also install it "straight up" vs. retarded which a lot of 351m cams are, and that helps a little also.

Tires, driving habits, basic tune up stuff are about all you can do otherwise.

http://www.cranecams.com/230-233.pdf

 

The factory timing on these engines are severly retarded from the factory. Since your engine is stock I am going to assume the timing chain is more than likely as well. You will be money and time ahead to buy a timing chain and reset the timing.

A cam will help the engine preform better and in some cases up the dynamic compression, but no the static. You can bump the static compression slightly by pulling the heads and having them decked at a machine shop.

Getting air in and out more freely should help as well. A cheap set of painted headers and free flowing exhaust will do good. An aluminum intake will flow much better than stock and should produce some gains. With the intake you will need to get a 4 barrel carb. Stick to something around 600-650cfm and a vacuum secondary- no 750 double pumpers.

Ignition upgrades such as a MSD ignition box and a hot coil will help get the most out of the fuel burn. A healthy spark helps you run lean and mean.

I would start with one of the cam/valve spring/timing chain kits. They are parts designed to work well with each other.

With all of that being said my warmed up 400 gets 12mpg driving around in town. Best of luck

 

Changing the timing chain makes a world of difference on the 351M. The stock chains are retarded 5 degree, and just get worse as they stretch. Get a 71' chain with no retard and they are completely different motor.

History of the Ford 351M

Rumors & Myths

351M/400 Performance Build Up

http://classic-web.archive.org/web/2...ts/parts03.htm

http://www.tmeyerinc.com/

 

i went fron 10-11 mpg on my 79 F250 4X4 351M with C-6 trans to 14-15 mpg simply by replacing the 2 BBL intake manifold and carb with an edelbrock 4 barrel EGR delete manifold, 600 CFM holley single feed single pump vac secondary carb, replaced the stock muffler and pipes with a high flow flowmaster delta 50 series 3 inch muffler off the y pipe and a turndown off the muffler, and set the timing by ear.

 

Thanks guys, good info here. This is all stuff I can do. I'm going to drive my rig around and see what MPG it gets stock for a month or so, then see what happens after some upgrades.

 

My 351cleveland engine gets about 12 around town. But it's got the edelbrock package. (Carb intake cam)

Not bad for town driving. I don't know what it gets highway. But it could be better...

 

i have also noticed in town driving sucks gas, because you are always in the throttle. if i drive it like a 90 year old grandma though, it will easily get 14-15 mpg.

 

.
. Yeah, the timing chain is retarded and as it wears/stretches it gets even more retarded... and the carb. is prolly jetted rich... also make sure the carb. float still floats...

http://www.summitracing.com/parts/su...FWho7AodpUQAvg

 

What gear oil are you running? Run lighter gear oil in differentials. Synthectics? Anything you can do to free up hrspwr is a good thing. Especially if in a winter world situation, oil cold and thick! Trim some fat off of truck any way you can? Clean out truck of crap if this applies, been guiltly of this myself on occasion! Skinny tires proper tire psi less rolling resistance! Good engine tune like mentioned! Timing chain!!!!