'77 F150 with 351M, needs to breathe!

[KRStone]

Morning all,

we have a project truck.

It appears to be stock. The engine needs to breathe! I'm not sure what I can take off and what needs to remain. No smog testing here. This is the "Fun" truck anyway.

Please post ideas here and I'll get up some pics to fuel the fire!

 

[rscurtis]

I had several parcel vans of that era with the 351 M engine. The '77 wasn't too bad, but the '78 had the next level of emissions hardware and was a real dog. It had almost no power and got 5-6 MPG. The only real problems were cracked exhaust manifolds and burned out mufflers from the heat. It's a good, solid engine platform (much better than what followed, IMO), but it will never be a power house.

 

[Dl5treez]

The 351M/400 engine series is a bit of a Heinz 57 child, and often disregarded by people as a boat anchor. They're actually a really great engine when they're built correctly.

They share the common 429/460 transmission bolt pattern, share many internal parts with the 351 Cleveland, and are relatively light for what they are.

They were cursed from the get go by FoMoCo with miserably low compression ratios and poor cylinder head designs.

The 400 is the 4" bore 4" stroke. the 351M is the 4" bore 3. 5" stroke. The piston height from wrist pin centerline to piston top on the 351M is taller than on the 400, due to them using the same connecting rods and having a 1/2" shorter crank stroke.

There are many possibilities to really make them run, and actually get decent (for a big gas engine) fuel economy. Some of the "tricks" come from the land down under...

 

[Wayne M.]

I once built a Cleveland for my cousin's same vintage Bronco. It was a fantastic engine, indeed the sister to the "M" engine. If you have no emissions to worry about, sky's the limit- rip it all off! The big problem is the super low compression. Personally, I'd do a dual plane aftermarket intake with a Holley 650 CFM vacuum secondary that is properly tuned (get a book if you don't have one), a nice cam and chain with good lift, short duration and overlap (to salvage compression), and a set of quality headers with a 2. 5" dual exhaust. It'll wake up nicely and you'll have fun! Except for the cam and chain, all the parts are cheap swap meet fodder.

 

[KRStone]

 

[Wayne M.]

BOY! that brings back memories. Is there a thermactor (AIR) pump on the other side of the engine? I don't think there's much in emissions on that puppy anyways. One thing that scares me just in the pix- the fuel line running over the distributor and wires... .

 

[KRStone]

I will need to fix that fuel line; wasn't even noticing the distributor since my diesel doesn't have one
I looked for a pump on the other side, is it belt driven? I didn't see anything belt driven.

land down under 'eh?

 

[Dl5treez]

Mechanical fuel pump... . down on the corner of the engine. Runs off a push rod from the cam... ... similar to how the mechanical lift pumps on a 12 valve work.

Ford sorta borked up the heads on the 351C/351M/400. The "2V" heads had small valves, small ports... good for low end... but, then they cursed them with open chambers, yielding low compression ratios when used with the standard flat top or dished pistons. I believe a 351M/400 compression ratio stock is 8. 2:1

The "4V" heads that were used on the hot rod 351C and Boss 302 were closed chambers, but with huge valves and huge ports. Like really huge ports... tennis balls could be crammed in them. Made good compression (9. 5-10:1)... . but really only start flowing good after about 4,500rpm, where a 351M/400 usually was near redline by that point.

So... there really isn't a good cylinder head from the factory for these engines... . or is there?

Enter the land "down under". Australian factory Ford 302 Cleveland heads. Closed chambers... small ports... small valves. Drop them on an otherwise stock 351M/400 and get compression ratios high enough to make good power, along with the small ports n valves to keep it on the bottom end. Much cheaper than the aftermarket aluminum options and a cool "cheater" part for guys racing back in the day who knew about the cool Aussie stuff.

Just search for "Aussie heads" on google and you'll see them. Or visit sites like ausfordparts.com and check them out.

My 400M loves Aussie heads..... muahahahaha... .

 

[Wayne M.]

I never knew about the Aussie heads... Kewl. Port and valve size wise the 2V's were ok, the compression ratio is bad. The Cleveland I mentioned prior was a 4V engine. it was a beast!