[DeTomaso] Exhaust Port Plates for conversion to 2bbl heads with4bbl headers
P. Rimov
rimov at charter.net
Sat Jul 26 11:26:38 EDT 2008
Ya know, even though the 4v style headers will bolt up to the 2v heads and
will seal on 2v Aussi heads and may or may not seal up on 2v US heads you
are not taking advantage of the flow characteristic of the 2v heads with
exhaust with ginormus primaries. The 2v closed chamber heads are designed to
produce power much lower in the RPM band than their 4v big brother so they
need an exhaust with smaller primaries for ideal performance and scavenging.
Technically they were designed as truck head for lots of compression and low
end umph. I have used exhaust with 2, 1 3/4 and 1 5/8 primaries on my 2v
Assui heads and the 1 5/8 out perform the larger diameter headers in terms
of throttle response and over all performance hands down. Power is right of
idle and good till 6000 even with a 2v Performer manifold. I am sure Dan
Jones will chime in on this thread sooner or later.
As a note the 2v Aussi head lack the 4000 rpm kick 4v heads have when they
really start to flow. They have much more linear power. And, I have found
the best way to get a super leak free seal is to have the header's flange
surfaced by a competent machine shop. I also like the way Percy's dead soft
aluminum gaskets seal over composite or copper gaskets.
Cheers
Paul
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