Joe:
If you have the early head, and your measurement gives approx
8.6:1, then your
head is stock. The early heads had a factory rated 8.5:1 CR, close
enough to your measurement.
The Goodparts table is correct for either type of head, hence
the lack of any specification as for which head it is valid. The
differences in the late vs. early head are mainly valve size, port
spacing, and port shape. The later heads have the better ports (which
the UK versions had from day one) which was meant to partially offset
the drastic drop in compression ratio.
I am not sure what "discrepancy" you are referring to. If you
are not getting the same chamber volume as the Goodpart table, did you
remember to include the head gasket volume? Depends on which head gasket
you use, but the gasket adds 4.5cc according to Vizard, slightly less
according to others.
Cheers,
Vance
-----Original Message-----
From: owner-6pack@autox.team.net [mailto:owner-6pack@autox.team.net] On
Behalf Of Lizirbydavis@cs.com
Sent: Thursday, January 29, 2004 5:59 AM
To: RazorBobSr@aol.com
Cc: 6pack@autox.team.net
Subject: Re: push rod length
Thanks for the reply Bob,
I have the early head. My head measures 3.462, which works out to 8.6
(I assume the DPO skimmed the head at some point.) Would it make a
difference in figuring how much to mill the head if it is low vs. higher
compression? Wouldn't the end result be the same? I'm looking at the
compression stats @Richard Goods' web sight. He doesn't specify early
vs. late head. I planned to mill to 3.415. I haven't cc'd the chamber
yet. I am concerned about my math, because Richard Goods' chart says a
head that measures 3.415 (compression 9.5:1) has a combustion volume of
45cc...Any ideas about the descrepancy?
Joe
RazorBobSr@aol.com wrote:
>I dont know what yr head u have but if its a low CR head these are the
>numbers u should be looking for,combustions chamber 49ccs,and head
thickness AFTER
>milling to get 9.5[3.415] Highter than that will put u in the DET range
for reg
>gas,I just did what u are thinking of and have eng set up much the same
as
>yours.You can spend about @#$%^& dollers have eng ported,OR u can do it
yourself
>as winter thing,unlesssss u are going for MAX HP??? Theres lots of iron
that
>can be removed from intake ports with drill and some stones,then
finnish with
>wheel cyl honning tool,use old ex valve as template.DO NOT make ports
>bigger,DO make them smoother,while u have head off and valves out,use
drill and stones
>to open up intake valves pockets[under valves] and u could go to larger
>intake valves.Bob 74
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