I have a stock 1978 f250 custom 4x4 with a 351m/400 in it. i want to know, what should my HP at the wheels be and how much torque am i producing? anyone with accurate info please share

 

is it a 351m OR a 400?

 

Originally Posted by Mil1ion
Did this work ?

Model Year
Engine ......Horsepower @ RPM
(SAE net, except '71)
Torque (ft/lbs)..... @ RPM

1971* .....400 (car only)
.......260 @ 4400

1972.......400 (car only)
.........172 @ 4000..........298 @ 2200

1973.......400 (car only)
....171 @ 4000

1974......400 (car only)
170 @ 4000

1975.......351M (car only)
148 @ 3400

1975......400 (car only)
158 @ 3800

1976.......351M (car only)
152 @ 3400

1976........400 (car only)
180 @ 3800

1977.....351M (car/truck)
161 @ 3400

1977......400 (car/truck)
173 @ 3800 / 158 @ 3800

1978.....351M (car/truck)
152 @ 3400 / 156 @ 4000
Torque — / 262 @ 2000

1978......400 (car/truck)
160 @ 3800 / 158 @ 3800
Torque — / 276 @ 2000

1979.....351M (car/truck)
151 @ 3400 / 156 @ 4000
Torque 262 @ 2000

1979.......400 (car/truck)
159 @ 3800 / 159 @ 3800
Torque 276 @ 2000

Remember, you'll loose about 20% of these numbers at the rear wheels

 

Can you be more specific?

 

Ok.....well maybe 15 - 20% loss at the rear wheels...depending on the health of the drivetrain.

 

Also parasitic loss from the engine being as old as it is. 1978 is not "fresh off the shop floor".

 

it is a 351 modified to 400 with a 2 barrel motor-craft carburetor manifolds with duel exhaust out the side just in front of the rear wheels i have 33in tires with 16.5 rims. i hope this is specific enough because i want to know how heavy of a load i can haul with this truck i know my grandpa used to use it to haul a steer in the bed but a steer doesn't way as much as a truck would on a trailer

 

A 351m and a 400 are two different engine displacements, thus they are 2 different engines.. Your truck will pull a vehicle on a car trailer no problems, assuming it is healthy and running good, regardless of engine displacement. I wouldn't be worried.

 

Since you have low range, I think you could pull over 40,000 lbs. with ease. You just can't go to fast.

 

^^^ what the heck 40,000lb with a single wheel 3/4 ton? He'll kill someone for sure.

 

A 351m is an engine built by ford using parts from both the 351c and the 400 engines the m stands for modified because they took the 351 block and Modified it to 400

"The engineers at Ford took the basic 351C block and modified it to power a whole new generation of environmentally-friendly cars and trucks. To start, Ford changed the transmission bell-housing pattern to match that of the larger 429/460 engines. This would allow Ford to continue putting the larger, heavy-duty 460 C6 transmissions with the new 400 engines. Ford also enlarged the main journal diameter from 2.75 inches to 3.0 inches allowing for a greater bearing wear area. The crankshaft stroke was also increased from 3.5 inches to 4.0 inches for a 50 cubic inch increase in engine displacement and greater low-end torque. Finally, the deck height was increased 1.09 inches in order to accommodate the 400s larger stroke. Consequently, the intake manifold had to be widened approximately one inch to accommodate the new deck height. The rest of the engine remained virtually the same. In fact all of the 351C valve train components (except for the pushrods) interchange with 351M/ 400 engines. The 351M/400 cylinder heads will also interchange with the 351C 2brl heads, although the 351M/400 heads have 78.4cc combustions chamber where as the 351C 2V heads had a 76.2cc combustions chamber.To develop the 351M, Ford simply shortened the “throw” of the 400’s crankshaft to the original 3.5 inches used in the 351C. The larger 3.0 inch journal diameter of the 400 was retained in the 351M. To accommodate the shorter stroke, the compression height of the 400’s pistons had to be enlarged to raise the compression ratio up to 8.0:1. So, other than the crankshaft and pistons, the 351M is exactly the same as the 400 "

 

also im not planning on hauling 40,000lbs any time soon the truck is our farm truck and i want to know if it would be safe and worth it to put a goose neck hitch on it to haul our horses

 

You could most certainly put a gooseneck hitch on it to pull your horses. The truck will handle it just don't expect to go over any hills fast it will be a little gutless. Other than the lack of power its still a capable truck.