Oz head combustion chamber cc's?

[Anonymous]

Anyone measured or know offhand the combustion chamber cc's on a 250-2V Oz head? Just looking for some numbers to plug into a compression ratio calculator.

If anyone has gone so deep as to cc the intake and exhaust runners, that'd be spiffy to know, too.

gracias,

--mikey

 

[CobraSix]

Mine were 48cc, but was probably milled. Some people's are at 55-56cc, so about stock us size.

Slade

 

[Mike]

Mine measured 56cc. My machine shop said that it did not appear that the head had ever been milled.

Mike

 

[Anonymous]

Mikey.

When I CCd my stock aussie head I got between 56.6 and 58.6, and one at 59. I opened the small ones up to 58 and used that in my calculations. I now have a compression ratio of 9.8:1 using Ford 255-V8 pistons and milling .020" off the block. With a 280 deg cam a 3-45DCOE Webers it runs great!!

Hope this helps, Hotrod Bill

 

[AzCoupe]

Mine was 54, milled and cc'd the head for 52.

 

[Mustangaroo]

I have one that's 48cc ( been milled) and another head that's 58cc and doesn't appear to have been milled.

 

[michael_cini]

Glad to see this topic. I just had my 250-2v head cc'd and with a light skim the machinist said it is 55cc. I will be installing it on my 75 US 250 block. How do I calculate what my compression ratio will be? Thanks guys.

Michael

 

[kukm66]

Michael, the one ou sold me was 55 cc.

I went .040 over and used flat top pistons and along with the 55 cc head I got 9.1 compression which is where I wanted it to be.

Link:

http://falconperformance.sundog.net/compcalculator.asp

 

[michael_cini]

Hi Don,

Thanks for the info and the link.

I know the Bore, Stroke, Combustion Chamber Volume, and Head Gasket Compressed Thickness, but what do I plug in for the categories below? I have a 75 stock 250 engine. Thanks for the help.

Head Gasket Bore Diameter [inches] 3.81
Piston To Deck Clearance [inches] .025
Select Piston Type Dished
Dish/Valve Relief/Dome Volume [positive cubic centimeters] 7
Volumetric Efficiency: 80
RPM: 4500

Did you get your OZ head on the engine? If so, how is it running?

Michael, the one you sold me was 55 cc.

I went .040 over and used flat top pistons and along with the 55 cc head I got 9.1 compression which is where I wanted it to be.

Link:

http://falconperformance.sundog.net/compcalculator.asp

 

[kukm66]

Gasket Diameter - you would have to know what you have, just leave it as is as it will not change the compresion that much.

Deck Clearance - numbers are for stock, not decked. Again you would have to know what you milled off. Some are decking their blocks to zero.

Piston Type - stock is dished and the rest of the numbers are based on stock types. I went with flat tops fo I selected that option.

Note that all of the nuimbers that were inserted as a default are factory specs from what I have seen. Also, I went to at least 3 other sited to cross check the numbers and all came up with the same compression ratio. Some of them did not have all of the extra calculations such as dish relief, etc.

I will not have the engine running for several months as I am still deciding on exhaust and other stuff. I am taking this slow. I put in stainless valves and had a 3 angle job with teflon seals and 289 springs installed. Yella Terra roller rockers are going to be installed.

 

[michael_cini]

Hi Don,

Thank you for all of your information. It helps!

Gasket Diameter - you would have to know what you have, just leave it as is as it will not change the compresion that much.

Deck Clearance - numbers are for stock, not decked. Again you would have to know what you milled off. Some are decking their blocks to zero.

Piston Type - stock is dished and the rest of the numbers are based on stock types. I went with flat tops fo I selected that option.

Note that all of the nuimbers that were inserted as a default are factory specs from what I have seen. Also, I went to at least 3 other sited to cross check the numbers and all came up with the same compression ratio. Some of them did not have all of the extra calculations such as dish relief, etc.

I will not have the engine running for several months as I am still deciding on exhaust and other stuff. I am taking this slow. I put in stainless valves and had a 3 angle job with teflon seals and 289 springs installed. Yella Terra roller rockers are going to be installed.