hi guys I have a 78 ford f-150 with a bone stick 351M engine in it and I just wanted to know what I could do to the 351M engine to get more power out of it? and how much power can I get out of it with out hurting the engine? thanks.

 

Welcome to this forum! Boy, did you come to the right place! This is the best of the web in my opinion. There is alot of experience here and people are willing to share what they know to anyone who takes the time to ask.

I came here as a rebuild first timer , and would never have attempted my rebuild without the help I've been getting. I settled for a mild, torque favoring build but there's some doing creative agressive build ups too.

If your wanting to stay 351M your options are limited. Since it's a 400 block, most will advise building it as a 400, which is what it was engineered to be originally, and inherently yields the most power from this engine.

I know I haven't answered your question, but you've stepped into a world of experimenting enthusiasts who are still pushing the limits of this engine, and their properly verifying the results on the dyno too.

Sit back, more to come and hope you stick with this, it's been very rewarding for me.

 

what parts would I need to build it as a 400? thanks

 

The only difference is the crank and pistons. Those engines had a bad a cam design. They made them offset.(emissions attempt) The cam in there would be 4 degrees retarded unless its been swapped out. An aftermarket cam should work wonders for you.

 

The main difference is the stroke of the cranks. This is what makes the 400 standout from the other engines in its class-- it has a 4" throw, vs. the 3.5" throw of 351M. You might start by doing some background reading on the differences between the 351M and the 400.

You might try

http://www.clubfte.com/users/mil1ion...atedLinks.html and
http://home.earthlink.net/~bubbaf250/

These links are to sites where someone put alot of time and care to the research of this engine family. It will give you alot of good history and a background to the engine etc. , plus practical guide to rebuilding stock or custom. Also do a search on the 351M buildup here. Parts are somewhat hard to procur, especially for custom rebuilds. This engine isn't a Ch#$vy 350 after all, but there's a couple people here that will help a whole lot with availability and i would recommend using them in favor of the route I took. They've got good prices too, but ordering takes a little preplanning. Come back here and repost for a good recipe after you've narrowed down the purpose / intended use of the engine.... mine was torque favoring truck for pulling, for example. Each build is different based on this.

 

my truck is 2wd so I want it to be a hot street engine. that I can use to smoke the tires with sometimes. my boss at work just bought a 68 ford f-100 with a 460 in it. how much more power does the 460 have over the 400 and 351's? thanks

 

That's kinda like asking how does an orange taste different than an apple. During the mid 70s the smog police kicked the guts out of all engines. The mid 70s 460s were weak, low compression pigs compared to the fire breathers built in the late 60s/early 70s. Spend some time searching through the posts in this forum for all kinds of 400 recipes. Just remember that a "hot street engine" that'll smoke the tires is really going to be about torque, not horsepower. HP is just a calculation of torque, time & distance. If you want to build a motor that has impressive HP numbers be prepared to spend big bux to make it live in the upper RPM range. You want to build an engine that builds big torque as quickly as possible. That's the beauty of the 400, it has a longer stroke than the 460 and will build torque sooner. Can a 460 be built to make more power more easily? Yes. There is no substitute for the extra 60 cubes but if you want to keep the same engine in your truck you can easily get another 49 cubes out of your 351 just by changing the crank & pistons.

 

ok what crank and pistons do I need to buy to put in my 351 then do I just buy the pistons and crank for the 400 or what? thanks.

 

To convert it to a 400 all you need is the 400 crank and pistons. The 400 cranks are pretty stout so a junkyard crank could save you some bucks.

 

The one big thing I've learned from this site about this engine is that it was crippled from the factory in an attempt to meet emission requirement. Changing out the cam and timing set help this quite a bit. As with all engines, good breathing is important, so intake and exhaust are worthwhile.

Check out the article that Dave wrote at
https://www.ford-trucks.com/article/...00_Engine.html
As a comparison, a 460 is a bigger motor, so it's possible to build it to have more power. But the 351M/400 engine has plenty of potential, and it's lighter.

Above all, have fun and build something you'll be proud of.

 

ok guys I talked to my boss today he has a mechanic shop and i work for him and another guy in their tire shop but he has a 400 engine and I asked him how much he wanted for it and he said that I could just have it and to come and get it. should I go and get it and then just rebuild it and put it in my truck?. and would the c6 tranny bolt up to the 400?

 

Nice. Yes, get the 400. Chances are that it's a truck 400 with a rear sump. It's likely that the C6 has the right bellhousing bolt pattern.

I would take a conservative, low buck approach to rebuilding for torque. The stock cam will work if you get the right timing chain. If you can degree the cam, that would be a huge help. After that, the challenge is tuning the carb and distributor. I think you can well over 400 ft/lbs of torque and probably an easy 250hp just by tuning it.

If you are a little ambitious, you can install 460 intake valves (2.09") and port the pockets. As Bill said, aim for torque, not horsepower.

 

it would be awsome if I could get 250hp and 400 ft lbs of torgue out of the 400 that would make me a very happy camper. i will go look at the engine on saturday if i have the day off from work as long and the clock doesn't have any cracks in it I will probably take it and do a rebuild on it thanks for your advice. one more question will the c6 tranny hold up to all that torque and hp?. thanks

 

As for will the c6 fit. It will if it was the c6 hooked to your 351m. The 351m, 400, 429 and 460 are all the same bolt pattern at the tranny. As for a c6 holding up to that amount of power it will hold up to that and much more.

 

how much power will a c6 tarnny hold up under? thanks and how can I tell when the engine was built is there a mark on the engine or anything?