78 F150 Engine upgrade
More Turbo
Joined: Oct 2006
Posts: 632
Likes: 40
All good advice regarding cam advance, makes a BIG difference on 351M/400 engines, especially when coupled with a max 600 cfm 4 bbl carb/dual plane intake (Performer, etc). Highly recommend upgrading to 400. 1/2" more stroke =noticeable torque increase. All you need is source 400 crank and pistons. Block, rods, heads all the same. The harmonic balancers were different in appearance from the factory, 400 thicker than 351M, but I always heard/read the replacement part from Ford was the same. Not 100% sure on that.
Fleet Mechanic
Joined: Feb 2004
Posts: 1,509
Likes: 333
From: Arlington,Wa
The original 351M that I started with ran great, had awesome power and great reliability until the fuel pump went which leaked gas into the oil and chewed up the conn rod bearings. And that happened at 185K miles. Im sure it would have easily made it to 200K if it wasn't for the fuel pump. ( I didn't catch it in time). Also on that engine I was running a Comp Cams 268, Crane screw in stud kit and a new timing chain installed straight up. Edelbrock intake and a Carter 625 breathing through headers and glass pack mufflers. As for the LS question...I wouldn't do it. I'm sure there would be lots of fab work involved. As others have said....351M-400 will drop right in. A 460 or 429 will too but you need different motor mounts. Lots of threads on that swap.
More Turbo
Joined: Oct 2006
Posts: 632
Likes: 40
I have 2 79 Broncos I've done 460 swaps in. Both were early 90's EFI engines that I converted to carb, other than that all stock. Still have another 79 and a 78 with 400's, which have both had the cam advance and 4bbl intakes/carbs. Can't really tell any noticeable performance difference between the 460's vs 400's. I do realize the 460's have more potential, and the EFI engines were not hot performers by any means, but neither were the 400's factory either. The 460's look nicer with the serpentine belt setup, but driving one vs the other I wouldn't know the difference. I CAN tell a difference between an otherwise equal 351M vs 400. Due to the stroke difference no doubt. 400's have a 4" stroke which is even longer than the 460's at 3.85.
Elder User
Joined: Jun 2005
Posts: 542
Likes: 1
Not familiar with Atomic, but FITech systems seem to be relatively popular and cost-effective, depending on what you're going "driveability" wise. Nothing wrong with a well set-up 4BBL, but for a DD, I'm really really considering an FITech setup.
I have a box-stock 400 in one pickup, and a 351M in another with a dual-plane Edelbrock manifold, a Holley 4BBL, RV Cam of some sort (bought it that way, not sure what it is), straight-up timing, and headers, otherwise virtually the same pickups. Both are F250 4x4's, 4 speeds, 3.55's, stock tires - other than the 351M has a heavy flatbed and hoist compared to a regular box - and the 351M runs like a scalded dog compared to the 400. So even a mildly built 351M is a heck of an improvement over a stock anything from the late '70s........
What do you guys think as far as compression ratio / stroke? For a DD that will get pump gas and nothing fancy, are you better off with a 351M stroke? I only ask because I remember a couple 383 Chevys around here that were runners, but were a little too hot to run good on normal gas, they had to run premium AT LEAST - I'd like to stay away from that drama, and run anything in it.....
I have a box-stock 400 in one pickup, and a 351M in another with a dual-plane Edelbrock manifold, a Holley 4BBL, RV Cam of some sort (bought it that way, not sure what it is), straight-up timing, and headers, otherwise virtually the same pickups. Both are F250 4x4's, 4 speeds, 3.55's, stock tires - other than the 351M has a heavy flatbed and hoist compared to a regular box - and the 351M runs like a scalded dog compared to the 400. So even a mildly built 351M is a heck of an improvement over a stock anything from the late '70s........
What do you guys think as far as compression ratio / stroke? For a DD that will get pump gas and nothing fancy, are you better off with a 351M stroke? I only ask because I remember a couple 383 Chevys around here that were runners, but were a little too hot to run good on normal gas, they had to run premium AT LEAST - I'd like to stay away from that drama, and run anything in it.....
Postmaster
Joined: Nov 2011
Posts: 2,553
Likes: 10
Besides the bolt up issues, the 347 is a smaller displacement shorter stroke engine. It makes power at high RPM. A truck needs torque and lower RPM power... a moderately built 351m or better yet a 400 will work much better I think.
Elder User
Joined: Jun 2005
Posts: 542
Likes: 1
Ford started fuel injected 351W's in the late 80's(?). They weren't a really great design, according to most, and are still 25 year old technology. And, since NOTHING is really common between a Windsor, 335, or 385 engine family, there isn't much that will bolt on to an M - it's easier to put a Chevy TBI on it than another Ford part..... And they weren't great.
Fleet Owner
Joined: Dec 2009
Posts: 20,678
Likes: 82
From: NorCal
Well here's my take.... build a 400, port match the heads n intake, Terminator/Sniper/FI Tech/E-Street EFI, straight up timing, and headers with dual exhaust.
Doable, simple, and relatively cost effective.
Intake? Weiand Action Plus
Doable, simple, and relatively cost effective.
Intake? Weiand Action Plus
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Cargo Master
Joined: Sep 2013
Posts: 3,258
Likes: 1,321
From: Pryor, OK
How long have you had this truck? Did you change the oil when you bought it and if so, what oil did you use? The type of oil that you use at 3000 miles after a rebuild is critical to moving parts. I may be beating a dead horse here, but the correct oil to use has high levels of ZDDP (zinc) up to at least 5000 miles after build. I thought I was good to use normal conventional oil at 3000 miles after my rebuild and I wiped a cam lobe and lifter. Sounds just like a rod knock. My lower end was fine. All I had to do is replace the cam and all the lifters and I was good. I still use high zinc oil just for piece of mind.
Two months ago, I rode in a buddy's '79 Bronco with a bone stock '85 460. What a difference! He ditched his tired old 400 and he couldn't be happier. Claims he gets an average of 12.5 mpg, double the power, and it was a very easy install. He's also running on 33" MTs, C6, and 3.55 gears. I've gotten over $1500 in my rebuild and he has under $800 in his engine swap. It ticks me off when I really think about it. I could have install a 460 plus gone EFI for less than I have in my 351M.
Two months ago, I rode in a buddy's '79 Bronco with a bone stock '85 460. What a difference! He ditched his tired old 400 and he couldn't be happier. Claims he gets an average of 12.5 mpg, double the power, and it was a very easy install. He's also running on 33" MTs, C6, and 3.55 gears. I've gotten over $1500 in my rebuild and he has under $800 in his engine swap. It ticks me off when I really think about it. I could have install a 460 plus gone EFI for less than I have in my 351M.
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