. When I think of wheezing I think of the 4V Cleveland heads with ports that are way too big and really poorly shaped and because of all the internal turbulence, don't flow at all like they should for their size, just wheeze... like they have asthma... they look like they should make 600+ HP, but wheeze out at 300 or so in stock configuration... add some port plates and/or epoxy to make them smaller and straighter and they finally start to work...

. On the other hand, the air flows fast through the little Windsor ports for good MPG and mild street duty, but being too small, just can't get enough air to support high RPMs/horsepower... I have a 351W in my boat I ported the heads on till I struck water and combined with 2-eyebrow flat top pistons and a cam got a good boost in power from with more RPMs... but still well below my final combo with 195cc World Windsor Sr. heads, Holley 750 carb., and Eddy VictorJr. intake that gives about 425HP @ 5800 RPMs... and pulls well to 6500... it's .030" overbore makes it a '357 Magnum'... LOL!

. The 351M could perform well if not for the impracticalities that I mentioned in postings above... I have a 351M in my '78 F150, C6, 4WD, SuperCab, 8' bed, snowplow... which I need to make into a 400+...

 

Yeah compression is a limiting factor. I figured i could shave 010 to 020 off the block deck to gain some static compression. If i didnt hafta make adapters for an intake mani, i'd just port out and polish some M heads and stick em on my old W and maybe a bitty cam and call it a day but life aint that easy haha.

Windsors are great starting points (even thought about a bored out 302 for the truck with a good cam) but i want to be able to do it with an M just because not many have done it. Everyone strokes em out to 400's or swaps em out for 460's because its easy cubes.

 

I'm running an M in Rusty that does pretty well. It is bored .060" over and there is, or were, some forged pistons available in that size that give decent compression. But I'm not sure those are still available and I couldn't recommend boring that far anyway. So, I'd use Cleveland pistons and bush them down if I were building an M.

 

. Shaving .020" bumps the actual compression ratio up from about 7.6:1 to about 7.85:1... not really worth the $200 or whatever it costs to do that these days... more 351M's would get built if could just grab some decent pistons for it... I think TMI sells the KB hypereutectic 351C pistons already modded with 400 pins for less than most places ask for unmodded ones... might as well put the $200 toward the 400 conversion...

 

So whats a good cam for my 400 if I just rebuild my heads? Your saying shaving my heads is a waste of time? This truck doesn't see 2500 miles a year. I don't plan on rebuilding it, was just trying to get a little better running out of it.

 

Cam comments and recs here:

351M/400 Performance Build Up Camshaft & Valve Train

 

. If not raising the compression ratio, prolly should leave the cam size alone, just advance it at the timing chain/sprockets, and just go 4 bbl. carb. and headers/dual exhaust to recover any power lost there...

 

Wouldnt shaving the block .020 net more compression more than shaving the heads .020? Logic tells me that theres more cc's in a cylinder than a dome with identicle heights. It may not be a hell of a lot more, but its still more. I suppose theres no chevy or mopar rods i could make work in this motor to get compression up.

 

Cutting the block or heads may open up a can of worms. Too thin of a deck will not keep head gaskets. You may fubar your pushrod geometry.

As said above, if there was an easy way to make a 351m into a higher compression motor, it would be all over this board.

A low compression 351m is no economy champ and can't be much better than a 9ish 400.

I know you want to stay 351--is this some moral or religious vow or belief? Just give in to the pressure and go 400. You'll never regret it. Go ahead now, no one will think you are weak for going the easy way to big power....

 

I have no idea why you'd want to build up the dog of a 351M. If I had the option, I'd go 400 all the way! You're going to get about the same MPG with either one, but with much more torque.

 

. I plugged .020" off the bores into the compression calculator to get the numbers I posted... so... just the opposite, .020" off the chambers would be even less boost...

http://www.summitracing.com/popup/ca...ion-calculator

. Hot Rod did a famous 400 build that's in the stickies above using like Chevy rods and Chrysler pistons for about $5,000+... gets expensive adapting exotic parts together...

How We Got Over 500hp from Ford's 400M Engine - Hot Rod Magazine All Pages

. 'Cheap' build using bad pistons:

Ford 406 Engine Build - Hot Rod Magazine All Pages

. Near stock build:

http://www.classictrucks.com/tech/10...d/viewall.html

. I'm going to toss $300 TMI pistons and $150 400 crank/bearings into my 351M... along with Summit cam/lifters, Summit roller timing chain set... have $119 Summit headers, $50 swap Holley 650 Carb., $5 4bbl. to 2bbl. adapter, $50/pair swap new Hemi truck 3" Mufflers, some 3" S.S. pipes to connect it, 3" strap clamps...

http://www.tmeyerinc.com/product-p/kb2347.htm

. I expect a 9:1 400 to get better MPG than a 7:1 351M...
.

 

Not to mention that many times the pistons aren't down in the hole .020" so they might smack the head or valves.

Yup. Which is why my "stroked M" will be sporting 10.5:1.

 

Its no religious or moral value or any of that. Everyone just picks on em and tosses out the crank and pistons for 400 stuff. I kinda like my little ******* child M. Gutless wonder, for sure, but its another air pump, like all motors. Its more or less to show that just like every other air pump, a 351m can compete in the same engine size group. Plus, the engine only had 20k on it when i got it, so theres only 21k on it now lol (7 years, 1000 miles). I dont like to toss out nearly new parts. The engine runs great. I get about 10-12mpg at 50mph.

I was looking up connecting rods and stuff and seen that 240 six rods are longer. If i mixed and matched 240 rods (bored out a little on the big end) and some pistons from another 4" bore motor, ya think that might bump up compression a bit?

 

. I think the 6-banger 300" rods are used to make a 540" V8... 460 big bore block and 400 long stroke crank... just add up the 'stack height' on all the parts and see if it fits...

. By the time you have the 6-cyl. rods modified at both ends to the right diameter holes and narrowed, and some kind of pistons modded to fit them, plus $200 to re-balance it all, prolly cheaper to shell out $500-700 for custom 351M pistons of the proper compression height and stock balance weight... or go TMI/KB 400 pistons in Std. size and a 400 crank/bearing kit... sell your good 351M crank and pistons... keep the 351M stickers on the engine and tell everyone it's just a 500HP 500 lb.-ft. 351M... nobody will know the difference... hopefully get you to 15-20 MPG at 50 MPH... pay for itself with gas savings...

 

Lol 15-20 mpg. One can dream, right? I guess a 351 sorta sounds like a lost cause unless its a windsor or cleveland... or the new modular that has 660hp haha. Maybe tryin to get my dad to give me his 9:1 400 will be my best bet. Or just finding a windsor and porting the heads out and selling my intake and carb for 351w stuffs.

I guess 10-12 mpg aint too bad. It got 4-5 mpg with my old 36x14.50's on it.