Tom Kendall wrote:
<Snip>
Looks good Perry.
Tom Kendall should have some intake manifold castings anyday now.
Tom Kendall replied:
Good guess Paul! Got a call from the foundry today (Thursday). The
trial
casting is poured, "looks good", and I'll pick it up tomorrow
morning.
I'll
take it over to the machine shop and get it all cleaned up for
photos &
dimensional checks. Should have something posted within the week.
Don't know if I mentioned it before, but the guys at the foundry are
kind of
interested in this project. Seems the Pattern Shop foreman owns an
RX-7.
Has he seen your three rotor yet?
Paul Lamar
Tom Kendall responded:
I'm lugging the stock 3 rotor manifold with me to the foundry for them
to
eye-ball. I don't think they (or 99.9999% of anybody in this country)
knows
3 rotor engines exist.
I was looking it (the 20B manifold) over tonight, and noticed that
although
the ports on the block are different sizes (the same as the various 13B
ports), the runners all transition to identically sized diameters. Is
this
the case with the 13B stock manifold? On our version, the smaller ports
will have proportionally smaller runners. This should keep intake
velocities uniform throughout the runner length. Just a curious
deviation.
I doubt it will make any difference whatsoever.
Due to the nature of the three rotor it is not possible to do a dynamic
chamber manifold so a simple tuned manifold was used. Same goes for the
new RX8.
Paul Lamar
OK, that makes sense. The total stock intake tract length on the 20B seemed
very long. Made for a very tall engine too. Using the "wraparound"
philosophy of putting the intake plenum over on the plug side of the engine
instead of on top, I should be able to reduce the assembly height by several
inches.
The Casting: Got a first hand look at it today. Chunky little bugger, but
even unmachined, it weighed in at only 5 lbs. The cast surface finish
isn't nearly as nice as the stock ones, but certainly serviceable. All
major dimensional checks came out fine, and the machine shop should have it
skim cut & drilled some time next week. I was also pleased to find that the
as-cast "sockets" for stubbing in tubing bends came out 0.010 - 0.030
undersized (Yeah! How's *that* for accuracy in a casting!). Depending on
the quote, I'll see if the machine shop is willing to clean out these
counterbores.
The only disappointment is that the runner openings on the flange face are a
little oversized. Looks like I was a little too aggressive with the gouge
when I made the core boxes. But the geometry is good, and for the purist,
the surface finish should hold some JB weld real well for fairing in and
exactly matching the engine port openings.
I plan on mailing this first piece to Paul to be mated up with tubing bends
to see how it all fits up on a Real Engine.
I'll probably port the cast iron a bit to fit the manifold.
I got the tubing for the rest of it right here.
Paul Lamar
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