The Ford Barn - Flathead V8 Compression Ratios...6,020 choices

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Flathead V8 Compression Ratios...6,020 choices

There has been a one-page flathead compression ratio chart posted on the web, for several years created by David Fort, from the state of Washington . He created the chart for Ford & Mercury flatheads compression ratios around 2002. It was done in an Excel spreadsheet. I was able to contact him through the Fordbarn.com website. This chart was developed primarily for the 8BA series engines. About 2 years later, David told me, he revised the basic chart and was kind enough to e-mail me a copy of the revised chart as a file. His 2nd generation chart included piston dome cc’s information as well as head gasket cc’s info & valve counter bore cc’s info.
I’ve been retrieving other Ford & Mercury heads data & CR’s from other sources not only for the 8BA’s but also the 59A’s and 221 cu/in engines series. I discussed my data with Bruce Lancaster and he suggested I attempt to expand David’s chart . Bruce would send me additional original Ford & Mercury data to include in the revision. The information Bruce sent me also included Canadian Ford data.
The following is the result of the revisions and is attached the PDF file. Some things to note:
1. Compression ratio is a calculation of the (cylinder volume+ combustion chamber volume) divided by the (combustion chamber volume.), all converted to cc’s.
2. Piston dome configurations are available in several varieties most commonly round top dome and cone top dome. Calculations on the spreadsheet are done with standard Ford type cone top pistons. Using domed pistons reduces chamber volumes as the dome is above the deck area in the head. This measured dome volume data is entered as a minus (-) value.
3. As the bore of the cylinder increases the dome volume also increases. .
4. The volume of the cylinder head gasket affects the chamber volume of the head in the above equation. This data is entered as a plus (+) value. Only Best brand Graphite gaskets volumes were used for the calculations. Best gaskets are available for most Ford flatheads in GraphTite or copper. Armin Brown from Best Gaskets Company was kind enough to provide the cc’s and maximum bore sizes to me. GrapTite gaskets are listed with a compressed thickness of 0.057” and copper gaskets are listed as a compressed thickness of 0.055”. Over the years gasket materials may have changed as well as the thickness that could provide minor differences between Ford published data and my charts.
5. Best brand standard gaskets for the 8BA & 59A are good for bores up to 3.290”. Bores above that should use big bore gaskets either in GraphTite or copper that go to bores as large as 3.440. Best brand standard gaskets for the 59A engines should be used on the 19, 29, & 99 engines and are also good for bores up to 3.290”. Bores above that should use 59A big bore gaskets either in Graph Tite or copper that go to bores as large as 3.440. Data on charts reflects automatic change from standard gasket to big bore gasket when bore exceeds Standard Best gasket bore size.
6. Wikipedia suggests that compression ratios above 10:1 may create engine knock on today’s pump gas. Joe Abbin suggests a 9.1:1 ratio not be exceeded to run on today’s lower octane fuels. JWL suggest 9.7:1 not be exceeded so discretion in heads selection choices for your engine should be in your best judgment. Ratios that are above 9:1 are highlighted in yellow on the charts.
The spreadsheets use all the above data to calculate the CR of various heads with various bores and strokes. As the bore is increased the dome area is also increased subtracting the dome volume from the combustion chamber volume. As the stroke is increased the calculations reflect the resultant change. As the cc’s values increase between standard bore head gaskets and big bore gaskets this volume is also corrected in the spreadsheets.
Eighteen pages (including cover) are provided in the attached PDF charts; 2 sheets for the basic 239 cu/in engine. Included are standard Ford USA and Canadian factory heads data and aftermarket heads data from Denver, Offenhauser, Baron, Sharp, Edmonds, Eldelbrock, Sharp Navarro & Weiand. All calculations were done using Best Gaskets provided data listed on page 15. Some information also included on the same page is from the Fel-Pro Gasket Company but they do not provide any copper gaskets. None of the Fel-Pro gasket data was used in the calculations. The measured difference in thickness between the Best & Fel Pro gaskets are Fel Pro were thicker by 0.008”.
As aftermarket heads data was not a plentiful as the 221 cu/in data. As aftermarket heads data was not a plentiful as the 221 cu/in data.
If anyone has any additional heads data for the 239 or 221 cu/in engines I’d be happy to revise the file to include updated data.
Many thanks for David Fort, Bruce Lancaster, Joe Abbin, Armin Brown, JWL, Scott Miller and others for their input & data in this effort. Hopefully this data will be beneficial for use in our flathead Fords & Mercurys in future years.
Jim