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Mail From: Ted Mittelstaedt <agora!toybox.central.com!tedm>


Here is my observations on phenolic spacers:

First, let me say that I have never held much stock in cool cans, or icing
the intake manifold. The reason is that at full throttle the speed the
air is traveling in the manifold is so high that there is not any time
for it to dump any appreciable amount of heat into the manifold. My
observations on cooling fuel is that the ratio of fuel to air is not high
enough for even the coldest fuel to make any appreciable difference in the
intake temperature shot.

Most of the so-called gains I have seen at the track attributed to cool
cans are due to a much more important factor, fuel density.

By cooling the gas you make it more dense, and therefore the amount of
gas in the air is higher, your mixture is much more rich. Since most
stock carbs are jetted on the lean side due to emissions, just slapping
a cool can in the fuel circuit will almost certainly make the engine develop
more power. I think this has led to the practice of icing manifolds as
racers have grabbed onto this and gone wild with it.

Even if your carb is running red hot and heating the gas as it runs into
the fuel bowl, if you have adjusted the jetting in your carb to compensate
for this your still going to get the same mixture as if you have the jetting
screwed up and you compensate for it by messing with the fuel density.
Personally, I have always found it easier to carry around a box of jets
for this than to fool with ice and what not.

The one advantage you might find with a phenolic spacer is that it will
help to keep the carb temperature at a more even temp, so you don't have
the problem of sitting in at the starting line while your carb gas is
getting hotter and less dense. Otherwise, at full throttle enough gas is
probably going to be running through the carb that the spacers effects on
the tuned air circuit in the intake manifold is probably going to be as
significant as it's temperature effects, in other words probably nothing.