Relieved Block

[tubman]

Could you please share how you are able to get 11:1 compression on a relieved engine? Do you have a large displacement engine? Can you tell us how may ci?

[34PKUP]

Originally Posted by tubman

Could you please share how you are able to get 11:1 compression on a relieved engine? Do you have a large displacement engine? Can you tell us how may ci?

Did not say he got 11:1 compression but has "11:1 Offenhauser heads".
Everything else is just 'puffery'.

[tubman]

Originally Posted by 34PKUP

Did not say he got 11:1 compression but has "11:1 Offenhauser heads".
Everything else is just 'puffery'.

I'd really like to see what the O/P has to say.

[Vics Stuff]

Originally Posted by tubman

Could you please share how you are able to get 11:1 compression on a relieved engine? Do you have a large displacement engine? Can you tell us how may ci?

As mentioned I am running 11:1 Offenhauser heads . With the relieved block I figure that I was in the neighborhood of 9:1 compression ratio. I was not wanting to build anything radical , but just wanted a old school looking engine. I am also using baffles in the center exhaust port , Fenton cast iron headers and 12 VDC electrical system.
It runs on regular pump gas and reliable to drive.
Vic

[drolston]

Originally Posted by Vics Stuff

As mentioned I am running 11:1 Offenhauser heads . With the relieved block I figure that I was in the neighborhood of 9:1 compression ratio. I was not wanting to build anything radical , but just wanted a old school looking engine. I am also using baffles in the center exhaust port , Fenton cast iron headers and 12 VDC electrical system.
It runs on regular pump gas and reliable to drive.
Vic

Offy heads come with valve lift clearance specifications, not compression. Pretty much the only Offy heads around now are .400 and .425. Per the attached flathead compression chart, you can not get to 11:1 unless you are running a very big inch engine and .350 or .325 Offy heads.

Per the chart, my 284" factory relieved engine with .425 Offy heads has a compression ratio of 8.5, which is pretty close to optimum for a street engine. Runs strong with no pinging on regular gas and timing mark advanced 3 degrees.