Rob,
I do not claim to completely understand the phsics of the venturi valve
seat myself. I first picked the idea up because I was using the same
machine shop that Greg Solo's Engine Room uses, & the owner mentioned
the idea when I was discussing adding stellite valve seats. Knowing that
Greg was rebuilding the TR engine in Baby Doll, a sucessful vintage
racing Morgan, I went over to the Engine Room. I chatted with Greg for a
bit & inspected Baby Doll's head. Then I went back to the Machine shop
and told the owner to go ahead & install the seats upside down & cut a new
seat into the chamber side. When the seats were installed, I took the
head back, attached a corse high speed sanding wheel to a high speed tool,
poped it into each pocket & polished them out to the dia odf the outside of the
inside bevel. The head went back to the machine shop where the final valve
seat cuts were made.
Things to keep in mind:
1. Since the Id of the stellite valve seat is not changed, there is no
additional restriction from the stock valve seat.
2. Minimum clearance in the intake and exhaust system is between the valve
and the valve seat.
3. The fuel mixture is supposed to speed up as it goes through the pocket
venturi and flows into thechamber faster. It is supposed to also provide
a better distribution into the chamber. Greg said that he has had this
mod flow tested and there was a definite increase in airflow.
4. While widning the pocket, I was able to reshape it to make the curve from p
port to pocket more gentle (I noticed this while checking out Baby Doll's
head.
Anyway, I didn't through the idea out as gosphel, but as an idea to think
about.
Other changes to the head, Ports polished, 60 thousandths taken off the
head mating surface. Bronze valve guides installed. The protrusion
near the spark plug hole was removed (it was quite thin after machining).
This will require some beveling in the matching side of the cylinders.
Oversize intake valves were added, as was special valve springs.
While I'm at the top of the head;
The end of the rocker arms were resurfaced, and new threaded ends were placed
at the other end. New bushings were installed in the rocker arms and machined
to fit a new rocker arm shaft.The springs that fit onto the shaft to provide
horizontal spacing for the rocker arms, have been replaced by brass tubes.
This assures that the rockers will not move about on the shaft. Rocker arm
shafts have been known to brake in high reving TR engines. This happens at
ether end rocker arm. These rocker arms are hanging outside the pedistals.
I replaced the stock end pedistal with machined ones that support the end
arms on both sides. This required threading the inside ends of the
shafts and adding a threaded plug at each end.
Oh, the head itself, is a late TR4A head with al push rod tubes (earlier
heads had steel tubes. The TR4 head has slightly smaller dia intake ports
that provides a boost at lower & med RPMs with a slight penelty at the high
end. It makes the engine a little more flexable.
i recommend that you do not take 60 thousandths off either TR2 head nor the
early TR3 head. There is less metal between the bottom of the head and
the water jacket. Also, ecpect a clearance problem between the pocket in the
head for the thermostat and the cast water pump housing.
TR reved the head around '58 or '59 to add more metal between the bottom of
the head & the water jacket, and adding a diagonal flat to the underside of
thermostat pocket. This paovided more clearance between the head and the
water pump housing.
TeriAnn
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