Date:         Sun, 25 Apr 1999 11:07:18 -0700
Reply-To:     Tom Young <young@SHERLOCK.SIMS.BERKELEY.EDU>
Sender:       Vanagon Mailing List <vanagon@gerry.vanagon.com>
From:         Tom Young <young@SHERLOCK.SIMS.BERKELEY.EDU>
Subject:      Re: C.R. & Deck height
Comments: To: type2@type2.com
In-Reply-To:  <v01540b00b347c0622439@[207.224.204.90]>
Content-Type: TEXT/PLAIN; charset=US-ASCII

Since I'm unsure exactly what I've got in my two rebuilt heads (I
posted previously about this) and as someone had asked what the effect
of a flycut of .03" would be on the compression ratio, I decided to
build my own spreadsheet to calculate compression ratios, and see what
the effect of an "extra" or "missing" shim between the head and cylinder
would do to the compression ratio.  The thickness of the head shim
shipped with the gasket kit seems to be right at .031" or so, just about
the same as the above-mentioned flycut.

(My problem is that I have reuilt AMC heads and VW heads and I'm not sure
if I should be using the shim in the AMC heads, or not.)

The figures below labeled (calc) are calculated based on published figures
for a stock 2.0L Vanagon engine, or "typical" figures mentioned by
posters.  The (guess) figures come from other posts where people have either
reported the measurements they've taken or read about.

                                      Total    Compressed
                                     Volume      Volume

Swept area (calc)                   492.726        N/A
Piston dish (guess)                  17.000      17.000
Deck height (.04")(calc)              7.079       7.079
Combustion chamber (guess)           48.000      48.000
Shim (calc)                           5.482       5.482
                                  ---------   ---------  Ratio
                                    570.726      77.561   7.35
                                    =======     =======
Remove shim                         564.805      72.079   7.84
                                    =======     =======
Add extra shim                      575.769      83.043   6.93
                                    =======     =======

Clearly the addition or removal of a shim (or flycut) has a big effect on
the compression ratio.  Looks like I'm going to have to cc the heads or
risk some problems.  Sigh.
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Tom Young               young@sherlock.SIMS.Berkeley.EDU
Lafayette, CA  94549    '81 Vanagon
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