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The stock head has come completely apart.
Everything, but everything is punched out of it. Then it
goes to the porting room, where Bob Wilkinson - who's
generally known as Bob the RotoRooter - starts grinding
and hacking |
and beating. Interesting thing that's been found
out about Honda heads by R.C.: At one time, people
swore that the Kawasaki Z-1 was the optimum head design
around. Supposedly its flow could only be
increased some six percent. |
Byron Hines, main genius-type experimenter at R.C.,
discovered that the Honda head, on the contrary, can be
made to flow better than any Kawasaki head. Offset valve
guides are one big advantage which the Honda |
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has.
In addition to porting, the
ports get extensive reshaping. On the Cobra engine, each
individual chamber is not just opened up, but
individually cc'ed.
As a final thing, to make
sure the customer is happy with the bucks he's paid for
the item, Wilkinson pretties up the chamber. Doesn't
hurt, doesn't help. But it looks good.
On reassembly, the first item to go into place are the
R.C. valve guides. Stock Honda guides aren't, say, as
bad as stock Kawasaki items. But they're still not
really intended for high-speed strain. These alloy
items, R.C. has found, outlast stock or even bronze
items.
Of course, the valves are stainless steel, with hard
chroming on the stems and tips. These can be gotten
either in stock dimensions, or 2mm oversize for intake
and lmm oversize for exhaust.
With the hotter cam, and probable increased higher rpm,
the valves and guides will be subjected to far greater
loads than stock.
The valve springs are also trick items, being
manufactured of a silicone wire, and then tempered. They
are also stacked - installed to a predetermined height,
so that each valve has the same spring pressure.
Again, most of these parts aren't used for increased
performance so much as increased life.
The cam chain tensioner has been installed, and the head
goes into place. The head bolts are torqued in
accordance with the book specifications.
This thing is starting to look like a motorcycle engine,
instead of an assemblage of parts.
Now for the camshaft,
which is where things start to go to work. For the Cobra
engine, the R. C. 327 cam is used. It has specs like so:
intake timing--open 55 degrees BTDC,
closing at 90 degrees ABDC (stock, open at 5 degrees
BTDC, close at 30 degrees ABDC); exhaust open at 90
degrees BBDC, close at 59 degrees ATDC (stock, open 35
degrees BBDC, close 5 degrees ATDC). The cam provides
.373 lift intake, .385 exhaust lift (stock .3142
lift intake, .2945 exhaust). Stock cam figures, by
the way, vary widely -- there have been at least
three different stock cam configurations which we are
aware of and probably more.
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