Douglas Frank wrote:
>A while back someone mentioned port matching in the context of improving an
>intake header. What does it mean?
In simplest terms, matching the ports requires making sure the two mating
parts (manifold and head) form a smooth "tube" inside. If they do not
connect together exactly properly, there will be a "step" from one to
another. Imagine connecting two pieces of thick-walled pipe by butting them
together with a bolted flange. If they aren't exactly aligned (maybe the
hole in the pipe is not exactly in the center of one piece of pipe, or the
flanges are a little different from one another, or the bolt holes are too
loose and there's no way to fit the pipes exactly in alignment), then when
gas or liquid flows through the joint, it will travel over the resulting
"step" and turbulence will be created. This results in less flow capacity,
and (in an engine) less horsepower.
There are many methods of matching ports. First and foremost you must make
sure that the manifolds and head have some positive way of fitting together
in exactly tht same alignment each time they're reassembled - this may mean
boring holes in an open area of the flanges and installing a couple of dowel
pins into the head and manifold to hold the alignment. Then to provide some
reference to match the ports, one way to proceed is to make a rigid
(aluminum works well here) template, like a manifold gasket with small
holes. This must be fit to the studs or bolts that fasten the manifold, and
also to the alignment dowels. Carefully mark and grind out the holes in the
template to match either the mainfold or the head (do not grind the head or
manifold at this point, only the template), and then fit the template to the
other part and see how they fit. This will begin to show you where there is
a mismatch, and you can then decide how to grind the ports to match.
Now you need to decide whether you're porting or just matching, and go from
there. That's a huge subject in itself. Check out any good engine
modification book, and of course Kastner's excellent Competition Preparation
Manuals. You CAN do this yourself, just be careful and meticulous and ask
lots of questions before merrily grinding away!
- Karl Vacek
'66 TR4A - IRS
'64 Amphicar
'16 Ford T Touring
'46 Piper J-3 Cub
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