351m/400
I'll have to ease in on this one---. I have some experience w/400's and a lot of reading on Bronco sites. My brother had/has a 79 Bronc with a 400. Holly projection, Crane cam (old "Blazer" grind--too much duration for heavy vehicle), Full length headers, etc. Thing was really a "hoss", especially for about 5200 lbs. I have a 70 Mach I mustang w/351C 4bbl that I hope dosnt turn into dust in my garage before I can get back to it! The reason for all that info is that I do have some knowledge on the subject.
Hate to disagree XR7 Dave, but the 400 is not particularly big and certainly not heavy by big block standards. The 351W, 351C, 351M and 400 are considered "small blocks". Respective weights are W-525 lbs, C-550 lbs, 351M/400-575 lbs. The clevelands , M and 400 are all part of the 335 family of engines. The 385 series, 370,429,460 are all about 720 lbs. Even all the "FE" engines (332,352,360,390,428 and 427's (plus several other variants) all were over 600 lbs. But then, all this info is readily available in any of the Ford rebuild magazines.
Deck height for the 351M/400 is about 1 inch higher than the 351W. Bore spacing on 302's,351W,351C,351M/400 is all the same. 351M/400 has 460 bellhousing pattern and slightly different mounts. 351M/400 heads were open chambered as were clevelands after about 71-73. 400 heads have almost as much potential as 2bbl C's except for waterjacket in exaust valve area. 2 & 4 bbl C heads bolt right on and Edlebrock and Weiand both make a bolt on 4bbl intake. Adapters (price motorsports) are available for wide range of intakes. For that matter, Windsor heads will bolt on with minor plugging of a water jacket opening in the 335 series blocks. Intake adapters are available for that senario as well. As you probably already know, early 408 stroker cranks were made from 400 cranks, so main and rod journels are the same for the 351W and 351M/400. Cleveland had smaller Mains.
The heavy "boat anchor" image was because the 400/351M (in that order) series came along at a time when Detroit was appeasing the tree huggers. Just like the 460's of that era (I had one in a E250 van). Changing the crank gear for a "police interceptor" gear got the cam time back to either 8 or 16 degrees advanced which woke them up. Unfortunately the 400 was, except for the 71 year, severely down on compression. But then, gasoline was also extremely poor. 350 blazers and 360 mopars were not up to the task.
If it were not that these motors, even the Clevelands, are so obsoleted now, I would build one in a NY second. But just as I say that, I see that Edlebrock may be popping out aluminuim heads for them once again!! Also, flow figures for almost any of the aftermarket aluminum heads outflow the cleveland style heads. Unfortunately, for those who liked these engines, technology has caught us and the PIA factor makes these engines less than good choices.
Not trying to insult anyone, but much incorrect/uninformed info floating around about these engines. They are very capable of producing good horsepower and particularly good torque.
YB