Holley Carburetor Conversion
By Trev (MK3 ZEPHYR)
For
starter's you can use your original manifold, get yourself a spacer plate to
suit a Holley 350cfm or 500cfm two barrel. Now I can get this mod done for you at
your cost. It will be $330 Aussie dollars + postage and handling. When you
receive the inlet manifold make sure all is clean and use new gaskets to fit
the manifold on to the head. Mount the carbie with throttle shaft facing the
fire wall (The throttle shaft when you cut it and re weld is 165 mm from the
bend to the bracket with the ball on it), so cut it in the middle and re weld).
And as you can see I bent the carbie lever over and drilled a hole, and put the
bent part of the throttle shaft through it with a split pin in the linkage
hole. I then drilled another hole and used a bolt to secure the bracket onto
the Holley carbie shaft bracket
Note: If
you have a automatic gear box make sure to adjust the
linkage so it kicks down quicker, it lets the carbie and the engines rpm work
in better together.
When this
is all done it takes about 3 minutes to remove and 3 minutes to refit the carbie,
it works so well on the car, it now runs like a dream!
(a huge difference!). This was a well-spent project
and the car runs 90 % better than it ever did.
I would
like to thank Karl (Low Zep) for his help and
involvement in this project). You can talk to me about this if you like at mk3zephyr@bigpond.com
Thanks Trev -MK3 ZEPHYR
Parts needed:
1/ 1 x 350
Holley model 2300 Part Number (located on the choke air horn) LIST 7448
2/ 1x 350
Holley inlet to carbie gasket,
3/ 4 x 1/2
in x 5/16 x 1 in bolts,
4/ 1 x Air
cleaner suitable,
5/
distributor vacuum line,
6/ Fuel
line and filter,
7/ you
might need a fuel line adaptor to the carbie ,
8/ One
original intake manifold,
9/ a spacer
plate to suit Holley 350,
10/ a
welder or get someone to do it for you,
11/ A split pin and a small bolt and nut.
NOTE: In
the above photo, note the small spring captured by a bolt. This bolt head
(upside down) rides on the float chamber accelerator pump lever, mention of
this adjustment is in the below tuning article. The adjustment is made by
loosening or tightening the nut and bolt.
Tuning your Holley
2300 Two-barrel
By Karl Schluter. (LowZep)
(This will
also cross over to 4 barrel tuning).
First I
advise you to buy a new or rebuilt model or one of known history. 99% of tuning
any carburetor is fixing or chasing problems caused by people who read a
magazine and then had a play! Best to buy a HP or SA Workshop type Holley
manual, as these are Co- written with the help of Holley engineers. The Holley
is extremely tuneable, and easy to work with, they
have been used on factory cars from the performance years to the dark smog
years.
The model
best suited for the above swap by Trev is the 350cfm
LIST 7448 type two-barrel. These have a larger bolt pattern than Weber or
Stromberg carbs. You could use a smog spacer plate, a
Weber to Holley adaptor or cut a section of 20mm / 3/4” thick alloy block to
suit to weld to the Zephyr Mkl-ll-lll intake for the
fabricated intake base plate.
The Holley
7448 is about the same size as the Weber fitted to the MklV
V6. It is also of the two barrel non-staged opening type. This is unlike many
other Weber’s fitted to smaller cars. I find the dual opening timing a plus for
mid-range power if the engine is fitted with a mild cam. The staged opening may
gain slight mpg if the one-barrel is only used.
This Holley
should be fitted with the float adjustment fitting in the top centre of the
bowl (this is Holley’s race type bowl; it controls fuel better under cornering
etc). The other type of bowl has the float hinged at one end, this is a warning
of a factory fitted Holley robbed off another car, not the one you want for
this install. Holley’s were fitted on many cars and trucks, so again start with
the correct model (warning, a model like the 7448, the LIST 4412 is 500cfm,
much too big! However for those of you wanting to go bigger on a custom intake,
I suggest the 390cfm 4 barrel Holley, contact me for details).
The Holley
needle and seat can handle up to 8psi fuel pressure; the Zephyr’s stock pump is
fine if in good condition. If running an electric fuel pump, I advise you run a collusion switch, Fuel flow NZ sell a very good one,
check the FAQ/Part suppliers section on site.
The Holley
is easy to tune. e.g.; idle speed, idle mixture, main jetting, power valve (an
on/off switch for extra fuel on vacuum demand added alongside the main jet
fuel), are all easy to change.
If you are
keen to go into the carbie I suggest you buy the model 2300 two barrel rebuild
kit or gasket set, these gaskets can be brought on their own from speed shops
but beware they do differ if the gaskets are brought on their own. Use lip clap
stick on the gaskets so they don’t stick and can be reused next time. For extra
$$ you can buy non stick gaskets. Before installing the carbie make sure you
spot any vacuum ports that need capped off if unused.
The Holley
has a very tuneable accelerator system than can vary
the timing of fuel being sent into the carb relative
to throttle opening plus total volume and the volumes timing over different
throttle opening degrees.
However
most of these do not need changed, I would set the basic carbie up as I advise
in the following and if need be tune more on a rolling road.
First I
suggest you buy a vacuum gauge, this is useful to set idle mixture and PV
(Power valve) settings. I suggest any unknown carbie be given a basic run
through first, so take note of how the accelerator linkage to the underneath of
the front float bowl fits together ( I suggest you take a pic
etc),then take the float bowl off (undo the 4 bolts later models –Screws on
early models) .
Hold the
bowl upside down and using the float level adjuster (the slotted screw is the
adjusters lock so loosen it first), turn the hex nut left or right to change
float height. Warning: with some after market rebuild kits the nut is the lock and the screw changes the
float level-this is rare) take note of the main jet size (engraved on the jets
side: 61 is the stock size, and a good starting point). Also now check the
power valve sizing, it’s a large hex headed valve (stock should be 8.5), I use
a large open end spanner to remove mine from the fuel metering block and then
clean all traces of old gasket off the parts carefully. If you remove and replace
the power valve, only snug it into place, firmly but do not over tighten! If while tuning the cars engine the car
back fires, the power valve will need replaced.
Note a
raised rib around the one side of the metering block and one side of the float
bowl, these help seal the carb and also stop gasket
crush, don’t remove them with a file!.
Now making
sure the bowl and metering block align and the accelerator pump linkage fit in
together as before (you did take that pic?) bolt the carb’s 3 pieces together with the two gaskets. The bowl
screws are tightened in a crisscross manner firmly, again don’t over tighten..
Now because
the bowl has been removed the accelerator pump lever will need re-adjusted.
This is where many go wrong. There should be NO clearance in the linkage points
at any non-full throttle setting.
Holley ask for a clearance at WOF, (Wide Open Throttle). However if
you set it as per the following you will end up with ample clearance: adjust
the set-screw that holds a short spring in the accelerator linkage so that ANY
turning of the throttle butterflies immediately moves the accelerator pump arm.
A further check after the car has been run with the engine off is to check for
a squirt of fuel if the throttle is lightly touched. If there is not, undo the
set-screw and nut that holds the coiled spring on the pump linkage until the
slack is taken up. Read the above while viewing the throttle and accelerator
linkage and all will become clear!
Further
tuning of the accelerator pump can be done both by the pumps shooter nozzle in
the two barrels opening (the nozzle has its size stamped on its side, stock is:
.031” a .25, .028 and bigger are available) also the plastic snail like cam
installed in the shaft of the butterflies at the carbie linkage has a second setting
(by moving the set-screw to the second hole) and different profile cams shown
in different colours can be installed to modify the timing and amount of fuel
flow under acceleration.
With so
many settings being easy to do I advise starting with the mentioned stock
fitment of parts.
The idle
mixture is best base set at adjusting the side screws 3 half turns out either
side from lightly seated (either side of the metering block). Then once running
set the float level so fuel lightly weeps out of the inspection hole that has a
brass set screw covering it in the bowls side. Undo the lock screw and turn the
hex either way to raise or lower the fuel level as mentioned above. If the
level gets too high, you have to let the engine use the extra fuel before
resetting the bowls level. Be careful to only turn a quarter turn a time to
raise or lower the float then recheck the float bowls site hole fuel level.
Once done, re-tighten the lock screw and reinstall the inspection screw in the
float level inspection hole.
Now I would
recheck the idle mixture at a fast idle by using a vacuum gauge hooked up to a
port in the lower half of the carb or intake. I aim
for a smooth fast idle with no lean misfire and then I lower the idle speed to
stock Zephyr settings.
Next is to
find the correct power valve rating, the 6.5 to 8.5 is often the most chosen
but a cam change may effect this. Use the vacuum gauge again (same hook up) and
go with a power valve rated 1 to 1.5 numbers (inches) BELOW the engines
manifold vacuum (measured below the butterflies) reading at idle.
The main
jets only effect mixture at open road speed –NOT at idle. I suggest you try two
sizes either side of the stock jetting and (in a safe area) turn the engine off
after running at open road speed to remove a plug for reading, light grey to
tan is the best colour you can aim for by eye with today’s fuel. If the plug
smells of fuel go down in jet size, if its white-lean go up in number by two
jet sizes.
I do advise
you get the car set up on the rolling road for best performance, install new
plugs, tune the ignition side and go and book it in if you want to explore
further tuning.
OR
Now air
bleeds can be drilled, the channels to the power valve changed with fuse wire,
the PV holes changed, accelerator nozzle and cam type changed, lots of extra
tuning can be added. But 99% of it is not warranted and may make the car run
worse. Holley spent a lot of money developing these carburettors
so don’t go to far from the stock settings, often if
you have to, its telling you something else is wrong!
Karl-Low Zep To contact me for tuning hints
on multiple carb induction, Weber and Holley, email
me at
Avocalea@xtra.co.nz Also
read the Hot Engine Rebuild article on site for further Induction tips and
recommendations.
Disclaimer: The advice
and guidelines given in these articles are given in good faith. The owners
and managers of the Galeforce Zephyr site will take no responsibility for
any injuries or loss sustained while carrying out the described tasks and
procedures or any consequences arising. Please read the Safety First Article
Why not
do an Article on your Pride and Joy and have it featured on the home page or
spend an hour doing a technical article about anything you have done or know of
to do with these cars
We need more information for
this site, to make it bigger and better. Any information on these cars will be
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