This is longish, and has to do with head variations. If you are
interested in TR head modifications, you may want to read it. I'd like
some feedback on these observations. Thanks.
Terriann Wakeman published a chart a long time ago that charted the
appearance and dimensions of heads. It has been a great help, and was
very well done. Most TR performance folks have seen it. Since Kas's
manual says that 1-1/2" port heads are the best performers, we search
for heads with the flat on top and the chamfer on the bottom of the
water neck, which the 1-1/2" port heads had. So far so good.
I was puzzled about three heads I have and what they are. Here's what I
found:
#1 has a 1-5/8" port (at the face) with what appears to be a little
machining to get that diameter, no flat on top, and no water neck
chamfer. Obviously a TR3-early TR4 head.
#2 is most interesting to me. It has 1-9/16" ports at the manifold face,
a chamfer on the bottom of the water inlet, but no flat on top. I'm
deducing that this head was made after they stopped putting the manifold
face chamfer in the heads but prior to putting the flat on top (where
the number is stamped).
#3 has 1-9/16" ports at the manifold face, a chamfer on the bottom of
the water inlet, and a flat on top where numbers are stamped. Obviously
a later TR4 head that we call the 1-1/2" head, reputed to be the best
performer all round.
Furthermore, measuring all three heads every way I can, I find no
difference between the three in the inlet passages, other than the
chamfer right at the manifold face. The smallest diameter in the passage
of all three heads is 1-7/16" and the valve pockets seem to be
identical.
Here's what I'm deducing:
1. The head we know as the 1-1/2" port head really measures 1-9/16" at
the face.
2. Some heads were made without the flat on top, but with the chamfer
under the water neck and the so-called 1-1/2" port configuration. I
wonder how many of these we've thrown away, thinking they were the
"early" and less desirable head, because they didn't have that little
flat area on top.
3. All three of my heads seem to have the same port shape and dimensions
once you get away from the first 1/4" of the manifold face, leading me
to believe that you could make all of these heads perform identically by
eliminating the chamfer at the face. Interesting, since the late model
heads are getting harder and harder to find.
Comments? I'm really interested what others have observed..
--
uncle jack and New Blue
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