I have a '73 302 with the 8.229 deck height that is unique to the '73-'76 motors. Does anyone have any experience decking these blocks to the 8.206 of the '68-'72 and '77-up motors to regain that .5 compression? Has anyone taken a 302 below 8.206 and maintained stock pistons/valve reliefs/manifold surface/etc?

Thanks
Chris Seay
Bealeton, VA
'49 F1
'68 F100

 

[updated:LAST EDITED ON 17-Mar-02 AT 10:44 AM (EST)]>I have a '73 302 with the 8.229 deck height that is unique
>to the '73-'76 motors. Does anyone have any experience
>decking these blocks to the 8.206 of the '68-'72 and '77-up
>motors to regain that .5 compression? Has anyone taken a
>302 below 8.206 and maintained stock pistons/valve
>reliefs/manifold surface/etc?
>
>Thanks
>Chris Seay
>Bealeton, VA
>'49 F1
>'68 F100

"Deck Height" has two different meanings, one is the distance from the center line of the crank to the deck surface, the other is the distance from the top of the piston at TDC to the deck surface. Therefore I generally refer to the first definition as "block Height" and the second as the "deck height".

How much you can deck your block is determined by:
1-stroke (3" for 302)
2-length of rod (5.09" for 302)
3-compression height (distance from center of pin to deck)

To calculate the minimun block height (or zero deck height) you use this formula:

1/2 stroke + rod length + compression Ht = block height

Ford used a number of different compression Ht pistons over the course of the production of the 302, therefore you need to know the casting number of your pistons (if stock). Here are the compression Ht of the castings I've been able to find so far:

C8OE 611OS -1.585"
C9OE 611OU -1.585"
D3OE 611OBB -1.585"
D9OE 611OAA -1.585"

Z3392 C4-E -1.605" (this is an odd one, probably a preformance part)

E6SZ 610A -1.608"
E6SZ 6108BB -1.608"
E7TE 6110RB -1.608"
F6SE 6110LA -1.608"

E7ZE 6110DA -1.600"
F3ZE 6110AA -1.600"

These came from Silvolite's stock replacement lists.

You can zero deck your block if you use a stock type head gasket
(minimum compressed thickness of 0.040") to raise the compression and still use 87 octane gas.

Now, providing your motor is completely stock (and never been decked) and you have 5.09" rods, and 1.585" Compression Ht pistons then to zero deck your block you would have to remove 0.540" of material from the deck (8.229" - 1.5" - 5.09" - 1.585" = 0.054"). I would advise checking the lenght of your rods and the Compression Ht of your pistons before doing this though. Ford may have also used a different lenght rod as well as different pistons. I've never heard of a stock rod with a lenght other than 5.09" for the 302's but I don't know everything either.



"Life is a lifelong lesson.
The more you learn the more
you relize your not as wise
as you think." RCC