LT1 plenum update

[Bruce Plecan]

Scott & Bruce,
What are the issues that you will have with the Plenum
volume being too low?

Cylinder filling (@ WOT), and midrange response

   I am running a 6.8L LT1 (409) with a
slightly adjusted plenum (bigger throttle bore, and
ported runners, but overall probably about the 3L
mentioned).
One issue I have is that the idle is rather bad (according
to the computer) one sides BLM goes down, and the other
sides BLM goes up, and I can mostly stop this by adjusting
the TB blades closed so that the IAC runs higher, but then
of course the motor has issues staying running in gear or
with the AC on.  The problem also goes away at moderate throttle.  Would
this be the sort of issue that one would expect to see?

Not really,
sounds like the idle needs more work.
I like running as little IAC counts as possible, there are others thou that
like having it open.
I also, like to min the throttle follower.
Just a divibility thing as much as personal preference.
Bruce

And Scott how are you thinking about changing the TB?

Roger






-----Original Message-----
From: "owner-gmecm at diy-efi.org" <owner-gmecm at diy-efi.org> on behalf of
"Scott Peitzsch" <jlg-sep at mediaone.net>
Sent: Mon, 15 Jan 2001 12:42:19 -0500
To: "gmecm at diy-efi.org" <gmecm at diy-efi.org>
Subject: Re: LT1 plenum update

Bruce Plecan wrote:
>
> Woulda thought bigger then that,
> interesting,
> just gotta double or triple it now <g>
> Bruce

Actually, I just did my calculations and depending upon some dimensions
that need to be finalized, the new total volume will be somewhere
between 5.7L - 6.54L.  This will yield a plenum to displacement ratio
of between 1:1 up to 1.15:1.  Combined with some other cleanup work,
should provide a nice improvement in driveability and power.

-Scott
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