All those naysayers who said the 351 heads were not suitable for the 260
block are correct, not because of most of the reasons given, but because the
combustion chamber width is 3.9" & the bore is only 3.8". Plan B is to use
the original heads with hardened exhaust seats installed & some gasket
matching & the slightest bit of porting, just to remove the rough spots. I
will have the heads milled, I'm not sure how much at this point, but
probably about 0.020" and I'm still debating about decking the block, there
is room to remove over 0.010" without the pistons protruding. I'm looking
for a slight compression boost, stock is supposed to be 8.7 to 1, the goal
is 9 to 1.
The engine is just as I suspected, a virgin 260 with 3.800 bores & the
mildest of cams giving about 0.375 lift at the valve. The block has 3 soft
plugs per side. The cylinder heads are the later 260 heads with the casting
& valve sizes shared with the 289, 1.67 intake & 1.45 exhaust. As best as I
can interpret the numbers cast in the block, date code 4F30, the casting was
made on June 30, 1964. Both block & heads have casting prefix C4OE.
The engine could have been returned to service with a new set of head
gaskets, but it is showing it's age. There is about 0.010" taper/ridge in
the cylinders, the lifters are all concave instead of convex on the bottom &
the peaks on the cam lobe are not quite what they used to be. The oil rings
show visible wear to the point the expander has been polished by the
cylinder wall, the exhaust valve seats are on their way out and perhaps most
interesting, all 8 pistons have cracks on the lower skirts on 1 side of the
piston near the pin boss. I replaced the crankshaft bearings & oil pump
about a year ago but the crank is scored enough to require grinding, it
should clean up at 0.010"
I plan to use a cam that will get lift at the valve to about 0.420", I'm
looking for a strong bottom & midrange while increasing the top end. I
expect this concoction should yeild about 225HP. That should be enough to
keep me ahead of the Miata's.
Now it's time to find a good machine shop.
Happy Motoring
Doug Leithauser
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