AMC Eagle Den Forum

The Shop => Altered Eagles => Topic started by: Alcoatari on February 20, 2014, 05:59:38 PM

Title: 4.0 head swap compression ratio
Post by: Alcoatari on February 20, 2014, 05:59:38 PM
Just a quick couple questions for the more advanced AMC gurus...

For the 258 + 4.0 head swap, I am curious what the product displacement and compression ratio will be.

I know I have come across this info before, but cant seem to find it. A link, a formula, anything will help.

I have the #7120 4.0 head.

My stock 258 is 8.3:1 CR.

These answers to these questions will supplement some supercharging calculations.

Trying to decide if the head swap could potentially hurt a supercharging application. If the 4.0 head raises the compression ratio substantially, this could decrease detonation limited power. I wont be going after super high boost, I have pretty stock equipment, so I want to keep boost between 5-8psi.

I plan on using an aftercooler as well as water injection, and would like to be able to use pump gas, so I want to keep effective compression ratio relatively low.

Thanks
Title: Re: 4.0 head swap compression ratio
Post by: eaglefreek on February 20, 2014, 07:34:41 PM
What I have read is the combustion chambers on a 258 is 62cc and the 4.0l 57cc. 
Title: Re: 4.0 head swap compression ratio
Post by: Alcoatari on February 20, 2014, 08:47:45 PM
Sweet, that helps. That means I can probably get away with a thicker head gasket
Title: Re: 4.0 head swap compression ratio
Post by: Draekon on February 20, 2014, 10:03:03 PM
This calculator claims that 58cc is the most common size combustion chamber for a 4.0l
http://www.jeepstrokers.com/calculator/
Title: Re: 4.0 head swap compression ratio
Post by: Alcoatari on February 21, 2014, 05:22:09 PM
good link, thanks