It was also a 4 bolt block, It used the stonger factory rods (similar to 289 hi-performance, but slightly different), screw-in core plugs on the block - and obviously, the correct, fordged pistons to match the heads.
If the factory information is to be believed; the Boss block (similar to the SVO/Motorsports OTC offerings - A4 and later R302 - maybe the 289 Hi-performace block too?) were made of a different metal formulation, compared to regular passenger blocks.
So the question can be answered in many different ways, based on the focus of the question. The Boss 351 was not as specific as the Boss 302 - in my opinion. By the time of the Boss 351, the SCCA was allowing de-stroked engines to be used, if they configured under the 5 liter limit. Pontiac used a de-stroked 400, Chevy used the 350, and Chrysler used the 340. At least as much as I can remember of the Glory days of small block racing.
These are pretty much the same things that any serious street machine today would emulate, if not try to duplicate. As has been mentioned by so many magazines and articles - it wa s factory small block built on hot rod techniques.
<font size=-1>[ This Message was edited by: Beoweolf on 1/11/07 5:52am ]</font>
No there were many difference's like Beowolf says.The boss 351 had a solid cam,aluminium intake,750cfm carb ,open element air cleaner,forged pistons,4bolt main block,heat treated crank,high strength rod bolts,copper lead bearings..They reused the boss 302 custom exhaust manifolds but put bigger 2 1/4 inch dual exhaust and free flow mufflers on the car....Pretty much standard hot rod items today but very impressive from the factory back in the early 1970s..It's too bad the boss's were so rare.
Boss used steel gears. They also featured a higher volume oil pump than a standard Cleveland.
As for Boss 302's here's a general comparison:
Standard 302.......................Boss 302
2 bolt main block..................4 bolt main block
press in freeze plugs...........screw in freeze plugs
nodular cast iron crank.........forged steel crank
standard rods with 5/16 bolts....longer rods with 3/8 bolts
cast dished pistons................forged flat top pistons
very mild hydraulic cam.........lopey solid lifter cam
small port inline valve heads....large port canted valve heads
cast iron intake w/2V carb........cast aluminum intake w/4V carb
single point ignition.................dual point ignition
stock restrictive 289/302 exh. manifolds......large free flowing exh. manifolds
<font size=-1>[ This Message was edited by: TorinoStyle2 on 1/11/07 10:59am ]</font>
The Boss 302 also had the screw in core plugs like the Boss 429. Boss 351 didn't. Boss 302 went in Stangs and Cougars and the Boss 351 was a Stang only option. 69-70 Boss 302 heads are different since the 70 had smaller, 2.19 intakes.
Information about 351 Cleveland vs Boss 351 are not as consistent as they are for the 302 and 429. Books will say one thing but 1st hand experiences are usually different. Boss unique parts should have a Z for the 3rd digit in the casting number. I don't believe Ford used all the Boss 351 parts as originally intended.
According to books, the heads are supposed to have slightly larger combustion chambers to reduce valve shrouding and should have a D1ZE casting. I have yet to see one. I think most, if not all Boss 351s merely used standard 351C closed chamber heads that were machined for screw-in studs and guideplates.
I've never seen a 780 Holley on one either. Most of the intakes have been spreadbore, but an over-the-counter intake with a Holley flange was available with a Ford D1ZX-DA casting number.
Considering the low production numbers and all the inconsistent literature I don't think we'll ever be able to proove everything beyond a reasonable doubt.
With the Boss 351 being a one year only motor and knowing how Ford tended to put things together the way they felt like it that day, we will only have a general idea as noted above. The Boss 302 is easier - it's pretty specific, with the special heads, block, pistons, etc. As noted the Boss 351 used what were probably a lot of shelf parts. My block is a D0AE-L like in the link above, but doesn't carry the D1ZX mark. So it's not a boss, but the cost to get it machined up was Boss, I'm telling ya.
I also have a set of D1AE-GA heads, but they were non adjustable - before the machine shop got hold of them LOL. Can't make out the rest of the casting number in the pictures, but they are likely -GA castings also as that was about the only one that comes up as a closed head with a D1AE prefix. Note that a lot of books show the Boss 351 head as a D1ZE. So the Boss in the pictures used a more common closed chamber head that was probably machined on a special line. They list that casting in the in the part number section of the registry. No mention of the block being 2 or 4 bolt.
When I get the 4V together, the car will get some special stickers I made for the front end that say "BOSS 351...Falcon". That ought to get the bowtie people going.