Hey all!
I got a 351m for free from a buddy of mine. I went ahead last year and got all the machine work done (.030 overbore, line bored, reconditioned rods, deck milled .010 cam bearings/freeze plugs, crank .010 & polished) and am ready to assemble it. I wanted to make this engine a high compression ratio engine because i have never been around a 351m with anything above factory compression and factory cam Unfortunately, money didn't allow me to get the pistons I wanted, and the heads NEED a 3 angle valve grind. ( I bought them under the impression that that was already done.. Only paid $120 for both, so it wasn't a big deal!) As life always does, things have happened over the last year that have really drained me financially. I need to get this thing put together and put into the truck its going in, so I can try to sell it. My question is, is there a cam that will be significantly better than the smog cam that came in it, that will safely run with the factory springs, pushrods, rockers, etc. It would be great to have a cam geared towards mileage and power (If possible). Im not particular to any brand. Also, will any aftermarket cam come with a straight up timing set? Ive heard that is the thing to do with these engines.
Thanks!

 

You are at a significant disadvantage with the M as there aren't many pistons for that engine. If you have the time you'd be better off finding a 400 crank as there are far more pistons available for the 400 - and everything else is the same.

But, if you stay with the M I would suggest Comp's XE256H or XE262H cam. That will maximize low RPM torque and economy.

 

Yeah I got a great deal on the machine work, and couldn't find any (Cheaper than the machine work) 400 cranks in my area. I was told, famous last words, that you must change the rods out as well if you do a 400 crank in an M block 351. Is there any truth to this?

 

Can I safely run those cams without Comp's valve springs?

 

NONE WHATSOEVER! I had rods out of the $40 400 I recently bought and out of Dad's 351M in my hands today, and they are identical, down to the part #'s. So I'm taking the crank out of the $40 engine and making Dad's a 400. I'll use Tim's pistons, which he has made specifically for him by Keith Black. He has pistons for use with the stock heads, like you have, the Aussie 302C heads, and the TFS aluminum heads I'm going with.

 

I ran a Comp XE256 in a 351W using stock springs. The 256 has a bit less than .500" lift and the 262 is slightly over .500" So, the answer is yes.

 

Check them after assembly and make sure they don't coil bind.

IMO you'd be better off going with their kit.

You may have missed the 400 boat, but a decent cam is a going to be a substantial improvement for you.

 

I agree he would be better off with their kit, but stock springs will work - especially since he plans to sell the truck. And I also agree that a cam will wake the M up, big time.

 

Yeah I realize the kit would be ideal, but my wallet will not allow it as of now. Is the compression height of the 400 and 351m pistons the same? Or will they hit the head, or be a mile down in the hole? If I could use the 351m rods, with the already matched pistons that are on them, I might be able to swing a 400 crank, if i can find a good deal of course. That is the obvious, best mod to do, and It would probably bring more $$ in the end when I sell the truck. I made the mistake of letting the machine shop tell me whats best, and not doing my own research. That won't happen again haha.

 

The pistons are quite different. With the 1/2" longer stroke the 400 pistons have a 1/4" shorter compression height. So you can't mix 351M pistons with a 400 crank.

 

. Reading several of the 351M to 400 threads on here will give you a lot of background info on the problems with these engines and piston availability... unfortunately, it sounds like it comes a little late...

. There are no good off-the-shelf 351M rebuilder pistons... the stock ones sat too far down in the hole, and the general replacement ones sit even lower...

. I'd suggest using the stock cam, with an adjustable timing set to get it 'straight up' or slightly advanced, because your compression ratio is prolly now even lower than stock, and any bigger 'performance' cam is going to bleed off even more of what little compression ratio/MPG/torque you have left...

 

Last night I did a BUNCH of reading on here about the 351m…… Sounds to me like took the completely wrong avenue to rebuilding this thing.. So to do a 400 crank swap, I'd need a good 400 crank, 400 pistons (And it sounds to me like high CR pistons from TMI are the clear, best option) and then have the pistons installed and matched to cylinders… THEN, get a good Cam with matched valve springs and timing chain. I might be better off cutting my losses and selling the engine parts… Any thoughts? Just today a friend of mine offered me a 79 460 (low oil pressure) for $50… That might be the preferred engine to put in an F150… Any thoughts guys? I hate when people talk crap on the 351m and the 400, so it would be cool to use the 351m, but does it make sense to do so is a better question…

 

It comes down to what you want to do. Are you putting an engine in it to sell or to prove a point? (Neither are wrong or bad, but you just have to decide.)

I'm not going to say how much I'll have in the engine going in Dad's truck, but it started as a lowly 351M that wouldn't get out of its own way. However, with a 400 crank, Trick Flow heads, roller cam & lifters, Tim's 10.5:1 pistons, Weiand intake, Edelbrock carb, and headers the cost will be substantial. On the other hand, Tim and my machinist both say when I put it on the machinist's dyno it'll show 500/500, with the torque peaking at about 2500 and the horses peaking before 5500. Not bad for a "351M".

So, if you want to make a point about the 335 Series engines it can easily be done. The 400 has the longest stroke of any Ford V8, including the 460, and stroke equals mechanical advantage, which begats torque.

On the other hand, if you are just selling the truck you have a couple of options. The cleanest way is to put the 351M together, and a well-built M can be stout - I have one in Rusty. Or, you could go with the used 460, but I don't know what you'll have to do to make it work. Yes, the bolt pattern on the back is the same between the M and the 460, but the rear of the crank is ~1/2" further back on a 460. (I mated a 460's ZF5 to my M and know all about that.) So I don't know if you'll have problems hooking the M's transmission to the 460 as Ford used a different bell housing or transmission between the two engines. Further, you will probably have to replace the engine perches, the pieces that are bolted/riveted to the frame. The M/400 had specific perches and I doubt the 460 fits them using the standard mounts.

So, set your goal or purpose and then go from there.

 

Good advice.. That 351m "stroker" your building is going to be sick!! Cant wait to see the final numbers!
Some good news, called the machine shop that did all the work for me and told them my dilemma, the owner said he "might" have a good 400 crank and some flat top pistons (not sure what brand, specs or anything) and we could figure something out if he did. He also thought he had some 4v heads… I wouldn't put those on this engine, but would consider putting them on MY 400 in my 79 f350 once I get this other truck sold! So we will see what turns up at the machine shop tomorrow or the next day..

 

Thanks!

That is good news on your engine. But, I don't think I'd run 4V heads on a truck. They have way too large ports and require lots and LOTS of RPM to work. The stock 2V heads have large ports and valves. If you don't think so lay your heads beside a 351W heads. You'll find your 2V heads are what Windsor builders would LOVE to have. So those heads are adequate, flow wise. The problem they have is that they are open chamber so you won't get any quench and can't run as much compression as you could with something like the closed-chamber Aussie heads. But, they will work well with Tim's pistons at 9.5:1 and the engine will be very strong.