In one of uncle jack's minor hospital stays, to stave off boredom he
wrote up a "brain dump" on building a wet sleeve Triumph TR motor. It
was intended for sharing purposes, so I'll do just that. I'll post it
on my website in a bit, but here's the Head section (hopefully I don't
hit the message size limit):
Also, be very careful with the whole "port matching" deal - it's very
easy to do more harm than good. Jack and the flowbench found a
zillion things that obviously would improve flow that actually hurt
flow instead. Unfortunately, I don't know all of the tricks. Having
a little step in there is better than having the intake manifold
suddenly go to a larger diameter. You cannot go more than 7 degrees
from a "straight tube" or the flow separates from the sides and you
generate turbulence that actually reduces the effective diameter of
the tube. My head flows almost as good as the best one Jack did, and
the intake ports are 1 9/16" at the outer face and I run stock
diameter valves.
- Tony Drews
Head
1. Porting the head. I will tell you what to do to get about 80%
of the flow improvement that a professional head flower (crazy term)
will get.
2. Intake Size the ports per Kass book, 1-1/2 all the way from
the manifold face to the valve guide. Take most of the metal off of
the short side. Remove the bump that is just inside the manifold face
in the port, adjacent to the head bolt hole. Make the short side
radius just under the valve seat as smooth and consistent a radius as
possible. Leave the port just under the valve seat a little smaller
than the valve seat, so that when the machine shop puts in the three
angle competition valve seat, you get the full effect of the
velocity-inducing three angle seat.
3. Exhaust - with a long shank carbide cutter, remove the big
bump in the floor of the bowl where the guide comes through. When
viewed from above, if you had x-ray vision, you would see that the
path of the port is S-shaped, Remove metal from the inside of the S
closest to the valve. Removing more does not do much for flow.
4. Here are the instructions to the machine shop:
A. Clean the head thoroughly. Replace the rear freeze plug.
B. If they accidentally put a head with aluminum pushrod tubes in
a caustic tank, the tubes will disappear. Do not despair. It is really
easy to replace them with > aluminum tubing
C. The aluminum plug on the top of the head may leak. It is in a
threaded hole, and after removing, you can tap it to NPT and put a
pipe plug in it.
D. Tell them how much to mill. If they are a good shop, you can
just tell them the ccs you want in a combustion chamber and they can
mill to that. It is risky to take off more than .165 from the stock
head thickness of 3.xxx.
E. Install guides if you are using the bronze guides, they MUST
have .004 stem clearance. The shops take some convincing, but if
clearance is less in these old engines, the heat will cause the guide
to shrink and the valve to stick, perhaps destroying the entire
engine.
F. When you get the head back, put a small bead of JB Weld
around the edge of the rear freeze plug. Also chamfer the edge of the
combustion chamber to remove the hot spot corner created by the
milling operation.
G. Tell the machine shop the amount of lift of the valves, and
have them machine the valve guide accordingly.
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