[Spridgets] 295 head content

Ron Soave soavero at yahoo.com
Sun Mar 23 15:04:55 MST 2008


--- Jack Laird <jlaird237 at cox.net> wrote:
> The question is how much decking to keep the
> cylinder volume about the same or
> a bit less so the compression is just a bit higher.
> What do I need to tell my head guy needs to come
> off

Jack,
I would not rely on a predetermined amount - it's much
safer and easy to just do the math or have the
machinist do it:

To get a decent idea, you need 5 key volumes which add
the unswept volume, plus cylinder swept volume:

1) Distance from top of piston crown to top of block;
My latest motor is essentially flush with the deck on
purpose So that's 0.00 for our purposes.

2) Ring land volume.  Typical for my stuff is approx
.75 cc

3) Compressed head gasket volume. Usually our stuff is
stamped with thickness or the supplier can tell you
the volume directly (the holes aren't exactly round). 

4)Piston dish.  

5) Head chamber volume.  Have him cc it. 

So....

Add the unswept volumes.

Swept bore volume is bore x stroke. 

Compression ratio is swept/unswept.

Ron


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