Heat Riser Passages

[the hamiltons]

Scott,
I was interested in the intake manifold modification of plugging the
heat riser passages you described a few days ago. I have planned to do it
for some time. I didn't know there was a horsepower gain as well as the
other benefits. What is the best location for the 1\4" holes. Top, centre,
or bottom of the plugs? Is there a special electric choke to use or anything
unusual to be aware of?
Al Hamilton
Kingston, Ont

hamilton

 

[scott woodworth]

Al,

Just drill through the center. Boyle's law states that trapped
gasses exert equal pressure on all surfaces. So it's reasonable to
assume that the intake would be heated to the same temperature no matter
where you drill the plugs. The size of the hole is more important. Joe
Mondello told me that 1/4 inch hole through each plug would deliver the
right amount of heat for street driving.

All these plugs do is cut down on the excessive heat delivery to the
intake. They increase horsepower by keeping the intake cooler and
eliminating the intake charge cross contamination from opposite bank
cylinders.

I know this modification will slow down the choke opening by
reducing the amount of how air available for the choke thermostat. If
the choke doesn't open fast enough or all the way, just convert it to an
electrically heated unit.

- -Scott Woodworth