MYTH: I can pick up a tripwoer intake, mount three regular 2 bbls,
run rubber lines to a fuel block, make some linkage, and have a nice tripower
that runs just fine.
Fact: I hear this often when people look at the cost of my units.
It is certainly possible to do and I have tried it myself, years ago.
Regualr 2 bbls can be made to function in the end location. In fact, I
can supply the parts and advice to help you with that process. Regular
2 bbls are made to idle, and to provide and extra surge of fuel at low
manifold vacuum (via power valve.)
Consequently, regular 2 bbls have thin throttleblades (3/32") that
do not shut completely. If they did, the motor woul have no air or fuel
and die. They also have idle circuits. A tripower end carb has thicher
throttleblades (5/32") that close and seal tightly. Why? With no
idle circuits, any air leaking past the throttleblades constitutes a vacuum
leak, causing a lean condition.
When people run three regualr 2 bbls, they often screw shut the idle screws
on the end carbs. Then, they are forced to richen up the idle on the center
carb in attempt to compensate for the lean condition. Driving down the
highway with this mixture cannot be a good thing.
Certainly, linkage can be made to work using three regular 2 bbls. I have
seen some creative uses of rods and levers to accomplish this. However,
it looks cluttered and homemade. Actual tripower end carbs have a throttleshaft
that protrudes on the passenger side. This allows linkage to run on the
passenger side. Most streetrodders prefer this as it is the vintage look.
Remember the old Ansen linkage? There were many companies that made tripower
linkage kits not only for streetrodders, but to convert the old vacuum
linkage to mechanical. Many Pontiacs and Oldsmobiles came with vacuum
activated linkage that was not responsive. Solution? Go to your speed
shop and get a set of progressive mechanical linkage.
Certainly it is possible to get by with a tripower using three regualar
2 bbls. But, unless it is done correctly, the potential risks faced make
this a poor choice. I can assist you i doing the job correctly, supplying
the parts and advice to do the job. See the section "Parts for Sale"
for the parts you need to do the conversion yourself.
MYTH Tripowers are always problematic and hard to keep in tune.
FACT I don't know where this started, but you hear it often repeated
at car shows and swap meets. Think about it--a tripower is made up of
3 very simple 2-barrel carbs. The center carb supplies the fuel at all
times, except under full throttle. The end carbs are extremely simple.
They have no idle circuits, no power valve, or power piston, and no choke.
I do believe that even when these units were new they freightened many
merchanics and owners. I hear many stories at swap meets about people
having difficulty with their tripowers back in the 60s. Many stories end
with, "So, I took it off and put on a 4 bbl." This was not necessary
if they had only been able to find a mechanic who understood these relatively
MYTH The carburetors have to be "calibrated."
FACT What? Maybe a set of Weber side-drafts. I've got an original
motor manual from GM--no mention of calibration. The only adjustment on
end carbs is the float, and I suppose the rod to the accelerator pump.
You adjust the center carb exactly as if the car had a 2 barrel.
MYTH Tripower cars are prone to catching on fire.
FACT Well, there is some basis for this. Notice that Pontiac (as
well as Chevrolet, Oldsmobile and Cadillac) used metal fuel lines. When
owners rebuilt the carbs, these had to be disassembled. There are many
opportunities for leaks. On a SBC tripower with a common fuel block ,
I count 12 sites for possible leaks, versus 2 for a 4 barrel. Yes, back
in the 60,s the red translucent lines were popular. Most tripowers I buy
at swap meets or from individuals have rubber lines or evidence of them.
Don't ever use rubber ruel lines on a tripower. I have seen streetrodders
run thode old red lines over new aluminum lines on their tripower for
the nostalgia look. That makes sense.
MYTH I can take my tripower carbs to the local carb rebuilder,
he can rebuild them, he said so.
FACT Don't let anyone who isn't familiar with these carbs touch
them!! Yes, they can rebuild them and set the floats. But, unless they
understand tripowers, they won't know if your carbs are right in the first
place. They can't offer you any advice.
I recently got an e-mail asking for help. He had had a local mechanic
rebuild the tripower on a car he had just bought, a 60 Pontiac. It still
did not run right. He sent me pictures of the unit. The end carbs were
regular Rochester 2 bbls that had not been converted. All three had power
valves and idle circuits. It did not idle right. When all three carbs
opened up, so much fuel entered the maniflold that the engine would almost
die. His mechanic charged him to rebuild 3 carbs. "Tripower expert...not."