The eight (V8 engine used as example)things that go up and down.
Jim

 

I'll talk slower so you understand Jim.The C code 289 has 9.3:1 compression ratio. The A code 289 has 10.0:1 compresion ratio. You get more compression by having smaller chambers, so the A code chambers are smaller than the C code heads.

 

a code engine had flat top pistons c code had 5cc dish

 

Really?

 

yeah i think it was in the pistons

 

yup i have rebuilt both there are open and closed chamber 289 heads but the open were for low compression engines

 

There's dished pistons, domed pistons, notched pistons for valve clearance, flat top and many combinations of them. Part of the calculation for combustion chamber size is the deck height. It's not easy to measure except on flat tops, so when you cc heads you also need to cc a cylinder on an engine stand so the head surface is perfectely horizontal and the piston is at the top. The head gasket is also in the equation. All that volumn plus the bore and stroke make up the compression ratio formula. I helped out a bow tie guy blueprint a B/MP engine many years back. Sometimes you learn from the 'enemy'.
Jim

 

Let's not get away from this statement. You can talk about dished, notched and all that other stuff, but I am here to tell you that the A and C code had the same pistons, and that the difference in the compression ratio came from the different combustion chamber heads.

 

As I sit here in 72 degree weather, I'm sipping some burgundy and looking at the Ford Car Parts book and low and behold, there are different pistons for 2 barrel engines and 4 barrel engines for 289, HP is a different issue. The low compression 4V in 64 1/2 uses the 2V in 65 to 68. They do not list compression ratios. Do you want the section, page and part number?
Jim

 

That's a 289 low compression engine used in mustangs before the C code was invented. That's a D code which used large combustion chambers. Go back to drinking, and have one on me.