I started to examine the race tuned Zenith-Strombergs and found some
interesting details. I have never seen any documentation on race tuning
these carbs other than changing out the jetting. I am sure there are tech
articles covering modification since these were very popular carburetors but
seeing some of the details first hand is fascinating.
The first thing I noticed is the front flange at the intake has a radius
leading in. Of course this section highly polished through the throat of
the carb. I don't think they ran air intake horns on these carbs which
would have altered the torque peak to higher rpms. (In the notes for the
Daytona race they set the rev limit at 6000 noting that torque dropped off
by 7K)
The choke shafts have been filed and polished removing hard edges.
I can't tell if there are modifications to the air pistons
The brass butter fly valves have been polished and the shafts that retain
these have been flattened having a thinner (VERY THIN) rectangular cross
sections vs. the round. The edges on the shaft have radii added and
polished.
It appears that the gaskets have been match as well as the manifold.
The manifold is opened up and polished very well.
Oddly, on the two sets of carbs that I have, the right and left carbs have
been exchanged so that the fuel line intakes are on the outside which
eliminates that "T" fitting. Choke is only available on one carb.
Unfortunately, one of the sets of carbs had aluminum jet assemblies. The
aluminum barrel that holds the jet must have galled in the carb case and
striped out the treads on both the right and left. Basically, junk.
Oh well, lots of parts... the good set of Zenith-Strombergs may end up on my
Series V.
I also have one set of Zenith carbs that were prepared for racing. I
haven't had a chance to look those over. I am sure they are well detailed.
These will go back on the race car as soon as I have an engine together.
I haven't found out any more information on the two cams that I mentioned
last week. The Weber or the Hollywood Sports Car "G-Grind". The Hollywood
cam is mentioned in the Sports car Graphic article featuring Jerry Titus'
racing Alpine. It's the cam they chose to race with.
Steve
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