Thanks for sharing that Chris.
I also found it helpful to tie the carbs together with a brace (3 DCOE's in
my case). My brace doubles as a mount for the air box. It seems to even out
the load on the upper thackaray washers.
Mike
-----Original Message-----
From: owner-fot@autox.team.net [mailto:owner-fot@autox.team.net] On Behalf
Of Chris Kantarjiev
Sent: Monday, August 07, 2006 11:15 AM
To: fot@autox.team.net
Subject: RE: [FOT] Fuel Pressures
Long ago, when I was devouring everything I could about race car prep,
I ran across a passage in the Dave Bean Engineering catalog about
mounting DCOEs on four cylinder engines. It ran something like this ...
no, exactly like this, since I still have that very useful catalog
on my shelf:
---
Although there is little to choose between the performance of
thackeray wahser and rubber cushion grommets, each has its own
durability problem.
Thackeray washers experience metal fatigue, as any spring will, and
break, thus collapsing and reducing o-ring compression. The culprit,
of course, is high frequence engine vibration. 7,000 rpm seems to
be the magic number. Above that, 20 to 50 hours of running is about
all you can expect of the upper thackerays (which are the ones that
fail; the lower ones have little load on them and live forever).
The cushion grommets don't have this problem, but do have one of
their own. The inevitable fuel leakage out of the carb-manifold
joint will eventually attack and rot the lower grommet. The upper
ones, of course, have little fuel contact and last forever.
VOILA! Use thackerays on the bottom and grommets on the top for
optimum soft mount life. Simply purchase an extra pair of cushion
grommets and washer for each soft mount kit you buy. Then keep the
leftover pair of thackerays in your toolbox as spares. Sometimes
the obvious escapes us.
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