Jim:
Kas Kastner recommends 0 decking the block in his book on race
prepping a
TR6 engine. He stated (if I remember correctly - always iffy) that it
requires about 0.017"
to 0 deck the block.). When I built my engine I was not aware of the
virtues of 0 decking
the block, but had my block decked 0.010" anyway, with no problems
since. My machinist
recut the fire rings for me.
I have read that the distance from the top of the top ring to
the crown of the
piston can be a problem, as you want enough meat between the ring and
the crown to prevent
the top land from cracking if the cylinder gets into detonation. Since
you are not altering
the piston itself, this is obviously not a problem for you. But I have
not heard of the concern
about reducing the cylinder wall height. I suppose it might have the
same risks as reducing the
piston crown height, but maybe not.
In any event, remember that the fire ring groove will be filled
with a steel ring. So I cannot
see how the ring ends up any closer to the combustion flame front. The
distance to the flame front
is still the distance between the top ring and the crown. So if it were
me, I would ignore him, but
then that is me. Remember many of these guys have not worked on high
performance motors, and so
do not know what will work and what will not - so they tend to be very
conservative.
My machinist got the "deer in the headlights" look when I told
him I wanted my mini motor
overbored by 0.115". I spent a lot of time reassuring him that it would
work, based on all the
reading I did. I even showed him a book that said it would work. So he
did it. When I picked up
the block he was obviously relieved when he told me it had worked with
no problems (no breaking
into a water jacket, no exposed oil ways, etc).
If your machinist is still giving you the willies, an option
would be to 0 deck the block,
and use the earlier head gasket. The earlier head gasket does not
require fire rings cut in the
deck, and so would maximize the amount of cylinder wall margin. Depends
on your tolerance for
risk....
Cheers,
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 Jimmy Richards
Sent: Thursday, February 21, 2008 2:02 PM
To: 6pack@autox.team.net
Subject: [6pack] decking the block
Oh great ones,
<snip>
I also want to have the block zero decked. I assume that once the
material
is removed from the block that the recesses around the bores will need
to be
re cut. My machinist is stressing over the distance from the top of the
top
ring on the piston to the bottom of the recess in the cylinder bore. I
have
not seen this issue discussed on the list.
Is this something that I need to be concerned about?
Thanks,
Jimmy Richards
74 TR6
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