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From: hkr4627@acf4.UUCP (Hedley K. J. Rainnie)
Newsgroups: net.auto
Subject: Re: open-chambered motors?
Message-ID: <330022@acf4.UUCP>
Date: Tue, 12-Mar-85 23:44:00 EST
Article-I.D.: acf4.330022
Posted: Tue Mar 12 23:44:00 1985
Date-Received: Sat, 16-Mar-85 02:14:50 EST
References: <249@cmu-cs-g.ARPA>
Organization: New York University
Lines: 22

Open-chambered is a term peculiar to Rat motors.  It distinguishes the
two types of head design.  The closed chamber design was introduced in
the original Chevy 396 Big block in '65 and continued as the standard
head for all big blocks.  In 1969, Chevrolet introduced the open-chamber
design in 1969 for the ZL-1 aluminum racing motor and upgraded the L-88
to open chamber heads.  The open chamber heads have redesigned water jackets
allowing the designers to unshroud the spark plug and basically remove a
great deal of material from the chamber.  Thus, they flow considerably better
than the closed-chambered design.  In the seventies, Chevy installed the
open-chamber on a street engine, the LS-6 454, producing 425 hp.  Chevy
also made iron versions of the open chamber in the seventies.  The open
chambered head, since it has a larger chamber volume, requires a higher dome
piston to regain the same compression as a closed chamber head.  The open
chamber additionally has more efficient combustion characteristics, requiring
lower compression for equivalent power and produces lower emissions.

Why don't I have them on my 427?  They cost an arm and a leg.

(signed) Speed Racer

p.s. For those who know, please correct my facts on the open chamber head.
p.p.s. Most of my fact relate more to the Corvette than all of Chevrolet.