How many cc’s??

[Vanspeed]

How many cc’s are stock heads? How many cc’s are Snyders 6:1 heads? I have a post saved from a few years ago where Bob Johnston says a 5:5 is 149 and a 6:1 is 137. According to Snyders catalog a 6:1 is 152. Who is right?

[Jim Brierley]

I have a chart in my book, done by Dave Barker some years ago, showing compression ratios using different bore sizes. It shows 155 for standard bore, 6:1 head. And it shows about 240 cc's for 4.2:1.

[Vanspeed]

I bought a head and it measures 125 cc. Just trying to figure out the compression ratio of it.

[PC/SR]

This site has an on line calculator. Just plug in the numbers. http://www.csgnetwork.com/compcalc.html

[Nosetime]

@Vanspeed. Buy Jim's book!

[Jim Brierley]

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My chart shows 7.5:1 for 125 cc's, you'll need to add in the gasket volume, I've seen 16.877cc @ .050” thickness and 20.253cc @ .060”. Marco Tahtaras on Ford Barn says 17.474cc. I’ve been using 20cc, a nice round figure. 145 is about 6.5:1

[redmodelt]

Wouldn't any piston pop up negate the the added cc's for the gasket thickness? For example if the block had been decked or other reasons.

[Jim Brierley]

Good point redmodelt! Yes, piston pop-up means fewer cc's of combustion chamber volume. It's normally about .015" but should be measured. At least .040" clearance should be maintained between the piston and the head as rods will stretch at high RPM's.

[Vanspeed]

Thanks for the info guys. I have yet to pull the stock head to measure piston pop up if any.