QUESTION How do I find the "list" number on my carburetor?
ANSWER
The list number for most performance and factory 2 and 4 barrel
carburetors will be found stamped into the upper right hand corner of
the airhorn or sometimes called the choke tower. On the 4150 HP models
that do not have a choke tower the list number will be stamped into the
mainbody behind the throttle linkage. This number is used to identify
the carburetor and also used when needing service parts or renew kits.
QUESTION How do I adjust the fuel level on my carburetor?
ANSWER Setting the fuel level should be the first thing you do before attempting to make any
further adjustments.The float level should put the fuel level just below the bottom of
sight plug hole. You will make the adjustment with the vehicle on a level surface and
the engine idling. You will first remove the sight plug, then to make your adjustment
you will need to loosen the lock screw on the needle and seat. This will allow you to
turn the adjusting nut to raise or lower the float level. Each hex flat on the nut will
change the float level approximatly 1/32". When you have the fuel level just below
sight plug hole you will then tighten the lock screw and reinstall the sight hole plug.
Make sure you have a shop towel handy in case you have any fuel leaks from the
Sight plug or needle and seat adjusting nut.
QUESTION I have a camshaft with a long duration and a high lift. It will burn your eyes at a idle. What can I do to fix this?
ANSWER
The most common cause is an improperly rated power valve. You will
first need to choose the correct power valve for your application. This
is covered in another section of the Technical Information Library.
When you have a camshaft of this configuration it requires more air and
fuel for it to operate efficiently. This in turn requires you to raise
your curb idle screw to obtain the same given rpm that you had with a
stock camshaft. If you are having a problem with the air/fuel mixture
screws not making a difference then what happens is with turning the
curb idle screw in farther this will sometimes cause the throttle
plates to open too far and they will uncover the idle slots. This will
allow it to bypass the idle circuit and start pulling fuel from the
transfer slot. To correct this problem you can raise the secondary
throttle plates a little with the secondary adjusting screw allowing
more airflow into the engine. This will allow you to lower the primary
throttle plates so you will be able to get back into the idle circuit.
Another method would be to drill a 1/64" - 1/8" hole in each of the
primary throttle plates on the side closest to the transfer slot. This
will allow extra airflow into the carburetor also alowing you lower the
primary throttle plates.
QUESTION My vehicle has a stumble from a dead stop. What can I do to cure this?
ANSWER
The most common cause of a stumble is not having an adequate
accelerator pump shot. The first thing to do is to look at the
discharge nozzle and make sure you are getting a good strong pump shot.
If not then you need to inspect the pump diaphram for a hole or tear.
You will also need to make sure that the pump passage is clear from any
trash or debris. First you will need to check the adjustment on the
pump. To do this you will open the throttle all the way (WOT). Push the
pump arm lever down and then adjust the pump override spring to obtain
.015" clearance between the pump arm and lever. If you are having a
stumble and no black smoke out the tailpipe then you will need to
increase the shooter size. If it stumbles and you are getting black
smoke from the tailpipe then it will be nessasary to decrease the
shooter size.
QUESTION I have a vacuum secondary carburetor that bogs when the secondaries come in. What will cause this?
ANSWER
Bogging and hesitation are caused by the secondaries coming in to
quickly. You can install a heavier secondary spring and this will
prevent the secondary from coming in to soon. If the engine is sluggish
in response at full throttle then the secondaries may not be opening
soon enough. You will then need to go to a lighter spring.
QUESTION I can rev the engine when it is in park and the secondaries will not open. Why is this?
ANSWER
The secondaries will not open by free revving the engine. The engine
needs to be under a load before they will open. If you are still
uncertain if they are opening or not you can take a normal paperclip
and clip it onto the secondary diaphram rod. You will then push it up
against the bottom of the secondary diaphram housing, now you will need
to go out and drive the vehicle. When you return you will be able to
look at the position of the paperclip on the rod. If it is lower on the
rod then you can tell the secondaries opened and how far they opened.
This is useful in determining if you need a heavier or lighter
secondary spring.
QUESTION How do I know if a vacuum or mechanical carburetor is best for me?
ANSWER
For streetcars the vacuum secondary carburetor works best on midweight
or heavyweight cars with an automatic transmission. They are more
forgiving than a double pumper is because they work by sensing engine
load. The mechanical secondary carburetor is best on a lighter car with
radical camshaft and a lower gear and manual transmission or on a car
that is going to be used for racing purposes.
QUESTION
After I shut my car off and come back out the next morning there is gas
on the throttle shaft and puddled on the intake. What causes this?
ANSWER
This is usually caused by percolation. This is when the engine is shut
off and the engine temperature rises it causes the fuel to boil in the
bowl and leak out of the boosters. There are a couple of things you can
do to cure this one is make sure the fuel level is not too high. You
can also lower the fuel level about 1/8" below the sight plug hole and
this will cure it sometimes. The heat from the engine will rise into
the carburetor sometimes and will cause the fuel to boil. Installing a
phenolic heat spacer between the carburetor and the intake or a heat
shield can cure this. These parts will prevent heat from getting to the
carburetor and boiling the fuel.
QUESTION
I just bought a new carburetor and it has a warning that it will not
work with an overdrive transmission. What can I do about this?
ANSWER
This warning was placed with the carburetor because if not installed
properly with the correct transmission kickdown bracket for the GM
700R4 it will result in premature transmission failure. Part #20-95 and
the kickdown mounting stud part #20-40 will allow the proper adjustment
of the cable.
QUESTION How do I find my local Holley dealer?
ANSWER You can locate your nearest dealer by calling the dealer hotline at 1-800-2HOLLEY (1-800-246-5539).
QUESTION Can I buy directly from Holley?
ANSWER We do not sell direct to the public. All sales and warranty returns are handled through your Holley dealer.
|