Fordnatics List Archive

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Mail From: "Howard, James A." <(email redacted)> (James Howard)


Hello fellow fordnatics,

As you may or may not know, I am in the process of building a Windsor
for my 85 GT. I have most of the parts now, and the block, crank, and
connecting rods have been given the full treatment and are ready to roll.

One of the few things I have left to purchase are pistons, and after
doing some more research, I have stumbled across something I would like
to get some input from the list on.

The block is a '69 351W, fresh boil and bore .040
The crank is a '69 .010 ground and polished
The connecting rods are '69 -- fresh shotpeen, magnuflux, etc.
I will be running Edelbrock Performer RPM heads, with either 2.02, or 1.94
intake valves, and 1.6 exhaust. The heads have a 60cc nominal compression
chamber.

I want to run 9.5:1 to 10:1 compression, not more.

Here is my dilema:

To achieve this compression ratio with 60cc heads, on a 351, I need to run
a dish piston. This I don't like to do, as it will affect the burn.
(The piston I need is around a 13cc dish, which is easy to find.)
The other option that I thought of would be to find a piston with the
with a smaller compression height (wrist pin further up in the piston)
This would be more difficult, as the 69 block is already the shorter deck
height. Help. (heh)

1. Am I better off running a dish piston with a bigger compression height,
and then run the top of the piston flush with the deck, or
do I run a flat piston (if I can find a short one) further down in
the cylinder?

2. With the dish piston, will I still need to cut valve reliefs to
support the 2.02 intake valves?

3. With the flattop, would I still need bigger valve reliefs, even though
the piston doesn't come to the top of the deck?

4. Do I need to be smacked a few times, as I am missing something obvious?
(This I could hope for, I guess... *grin* )

Thanks for any/all information.

Jim

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Mail From: (email redacted) (Dave Williams)


-> intake valves, and 1.6 exhaust. The heads have a 60cc nominal
-> compression chamber.

That should give you around 10.5:1, depending on the volume of the
valve releifs and the head gasket. Is there some reason you want to
lower the CR further?


-> 2. With the dish piston, will I still need to cut valve reliefs to
-> support the 2.02 intake valves?

There's no way to tell until you do the trial assembly.


==(email redacted)=========================DoD# 978=======

This read-only message was archived from a public mail list.
Mail From: (email redacted) (Dave Williams)


-> Mainly, I am worried about detonation at advanced degrees of timing.
-> It will be a higher octane machine to begin with, but I would still
-> like to be able to pull up to Amoco and fill with silver or gold and
-> have no problems.

I really doubt you'd have any trouble at 10.5, particularly since the
actual CR would probably be under 10 by the time you add the valve
reliefs, gasket volume, and crevasse volume.

==(email redacted)=========================DoD# 978=======

This read-only message was archived from a public mail list.
Mail From: (email redacted) (Dave Williams)


-> The factory 4v (69--one year only) used true flat-tops, and a 60.4cc
-> combustion chamber. Assembled, it produced 10.7:1 compression.

351W swept volume:

4^2 * .7854 * 3.5 = 43.98 CID/cyl, * 16.39 = 720.87 cc/cyl


Assuming true flat tops, 60.4cc heads, no allowance for head gasket or
crevasse volume, zero deck: 720.87 / 60.4 = 11.93 CR.


If the engine indeed had flat tops with no valve reliefs, the pistons
came substantially short of the deck. You'd need 7cc, somewhere around
.035" negative.


==(email redacted)=========================DoD# 978=======