Shawn:
Raising the compression ratio by decking the block will get you
more power than raising the compression the same amount by milling the
head.
The reason is that with a decked block the piston comes closer
to the head, increasing "squish". This creates more turbulence and fuel
mixing in the chamber, for a more thorough burn. The closer the piston
comes to the head, the more squish you get, right up until the piston
crashes into the head and your new motor is reduced to scrap metal.
If you are hot rodding an engine and are pulling the block,
ALWAYS get your motor zero decked if your head has any squish area on
the head (Some motors have no squish at all, like the old Chrysler Hemi
motors and some Japanese 4 valve designs). If you have no squish area,
then it is a waste of time. But most motors have a squish (sometimes
call "quench") area designed in so you should go with a zero deck
height. This is why Kastner instructs you to deck the block (although he
does not say why) when prepping your motor. David Vizard also strongly
recommends it in his engine building books.
Confucius say "Learn the ways of the Zen masters, oh
grasshopper, and you will go fast"
Vance
-----Original Message-----
From: 6pack-bounces+vance.navarrette=intel.com@autox.team.net
[mailto:6pack-bounces+vance.navarrette=intel.com@autox.team.net] On
Behalf Of Shawn J. Loseke
Sent: January 05, 2008 8:22 AM
To: Foster, Stan; Derek
Cc: 6pack (6pack)
Subject: Re: [6pack] Compression Ratio Calculation
The best/most mechanically efficient method for increasing compression
is to
begine with a zero deck height. That way more of the combustion chamber
shape
can be saved. When you keep shrinking that chamber shape you completely
change
the burn characteristics. On race engines the pistons will actually
stand
proud of the blocks deck to maintain as much of the chamber as possible
before
cutting the head down. My pistons stand proud of the block by .013". I
was
originally looking for zero deck clearance but my machinist (who buildd
primarily circle track motors) went a little too far. Luckily, the
compressed
thickness of the head gasket is still enough to not cause any problems.
<snip>
Shawn J. Loseke
Fort Collins, CO
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