Tom,
I found this info on the "K" heads from the Small Block Musings discussion
group:
"Now for real thrills, take the 351 Windsor, which came out in 1968. Ford
made them until 1978 or so, then replaced them with the 351K, which is a
351W with a 302 head. Real 351 Windsors have 8 intake manifold bolts and
L-
shaped intake water passages. 351Ks have the rectangular 302 water
passages
and 6 intake bolts, the only difference between the K and a 302 being the
size of the head bolt holes - 1/2" on the 302, 9/16" on the K.
- Somewhere in the 1980s, Ford decided to rename the 351K back to 351W, but
they're all still Ks, and the heads don't directly interchange. Real 351
Windsor heads will leak water with K gaskets. And to top it off, Ford
even
announced a new "BOSS 351" for 1993, available over the counter in the
parts
department. Alas, the new "BOSS" is a 351K, not a Cleveland, just to
further confusion.
- Ford's engine families and nomenclature are crazy."
Here's the link:
http://www.angelfire.com/ar/dw42/sbf.htm
The "real" 351W's used longer valve stems and push rods. However, the
289/302 heads themselves are really the same in this regard, so I recommend
using the shorter valves which give you more clearance. With flat top
pistons, the 59cc 351W heads will give you a compression ratio on the low
9's.
I'm not sure about the question of hardened valve seats. From what I've
read, the problem with unleaded gasoline burning valves and seats has been
exaggerated. If you are going to run the engine hard, then you would want
stainless valves and probably valve seat inserts too. For anything like
normal driving though, I don't think it's really a problem; at least I have
never personally heard of a specific case to the contrary. Has anyone out
there in Tigerland had a burned valve problem you attribute to running
unleaded gas?
Bob
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