Howdy all, I was scrolling the internet in that I have a 1977 f-100 with a 351m engine. I was thinking about removing the pistons and the camshaft and switching it to a 400. I came across this bit of info in a article.

"As Ford planned a MY 1977 makeover for their light-duty truck line, they decided to replace the aging FE 360-390 engines with the M-block 351M and 400 engines. Before MY 1977, the M-block had only been available in cars, and only with an automatic transmission, so Ford redesigned the M-block for its truck debut.

Main bearing support webs were revised, particularly the #3 main (thrust) bearing support web, which was strengthened to withstand the force imparted by a clutch. This redesign for truck applications was the only major change in the M-block’s engine block design throughout its production life.

Several unique parts were developed for truck M-blocks, including flywheels for manual transmissions, harmonic balancers, and truck-specific intake and exhaust manifolds. The original “non-retarded” crankshaft timing gear was also re-introduced on truck engines.

Other than the strengthened D7TE truck block, the truck 351M was basically the same as the car engine, with truck-only 8.0:1 pistons and a slightly different camshaft. The truck 400 also used a truck-only piston that produced 8.4:1 compression ratio, and a slightly different camshaft with more lift at both intake and exhaust valves. In MY 1978, car M-blocks received the D7TE engine block enhancements in their own D8AE engine block."

M-Block 351M/400 History

link to article is here in that I don't want to steal info without credit. My main question with the info is with regards to the 351M. In the article this author claims that in 1977 the truck 351m's did not have the "retarded" camshaft. Can anyone validate that statement? Is there anyway for me to see if I have a retarded camshaft or not? Thanks for any help.

 

I did a cam swap on my '77 f150's 351m in 1986 or 87 and the stock lower timing gear (on crank) did retard the oem cam. I used a new set with three keyways, retarded, straight up, and advanced. I used advanced as best as I recall. Truck still runs.

I'll look down stairs, I may still have oem timing gears.

You do know that to change the 351m to a 400 means changing pistons and "crankshaft".

Likely what you meant.

 

yeap, crank. Wow. Sometimes what I type is not what I'm thinking. Thanks for the thoughts. Still probably going to do a swap. Just found it interesting that this article mentioned the trucks 351m had non-retarded crankshaft timing gear and I've been under the understanding that all 351m's had the retarded crankshaft timing gear and that is what gave them the 'm' moniker.

 

There's a lot of speculation about that "M", but prior to the 351M .... there already was the 351W and 351C .... and then Ford came out with a tall block 400 Cleveland to use in place of 390s and such in PCs .... and then they destroked the 400 to come back to a 351 .... and called it a "M".

The 351M and 400 never was offered by Ford in a hi performance version, it was designed to provide torque in a day of new emissions controls and falling fuel octanes. A 400's stock crank still provides the longest stroke in a Ford gasoline light truck / car V-8. Put some pistons with some compression in either the 351M or 400, add the right cam and intake .... and they'll make the power alright.

And if you haven't already seen it, here's a book any 351M / 400 / 429 / 460 owner should have. Not so much a "how to hot rod" book, it is a great source of just plain good knowledge. This is like my copy I've had since the '80s:



This is an updated edition .... at least it was done in the '90s?