3 times a charm. Supposely they are able to be used 3 times, so I'm told.

my god man....
your using 3 carbies..... everything has to be perfect...
dont skimp on on things like a $10 gasket or you'll be kicking yourself...

update...

changed out the gasket...it was the cuplrit.

now got the timing dead set at 36ish degrees with a locked dizzy...

got the engine to idle very decent, revs great, but driving it on the road is a completely different story.

the throttle is very temperamental...

from idle, in gear (under load) bogs a little, so rev it up a little more....

bogging is overcome, so drop the clutch, and car moves.

idle and rolling, feels good, so step on the throttle...and speed increases... this is good...

but after about 1/8 throttle input...the carbs fall on their ass...and sounds like the engine is not running...let off throttle, they pick right up... still slow, but accelerates...shift, back to bogging, feather clutch, add revs, drop clutch...accelerates slow....mash the throttle...nothing...pull back on throttle...comes back to life... so from idle to 1/8 throttle...runs fine.

2 steps forward..one step back...

these are new carbs... why is this crap happening to me?

_________________


Also Known As Clayton Pace

What is your fuel pressure at the end, or last carb to get fuel?

sounds like you've got some jetting issues.. ie: chokes / venturies..
can u right us up a list of your settings.....
its really easy to overcarborate...

emulsion tubes shouldnt do too much.. it should run fine with any and be alitlle rich or lean..

Standard Z engine
choke: 28
ventury: 3.5
pump jet: 45
Air jet: 180
Fuel: 125

Worked engine. 35/75 cam grind or 3 quarter race cam.
choke: 34 - 36
ventury: 3.5
pump jet: 45
Airjet: 200
Fuel jet: 140

radical engine.
choke 36 - 38
ventury 4.5
pumpjet: 45 - 50
Airjet: 200
Fuel jet 140 -150

i would reccomend using a 3.5 auxiliary ventury. this will keep it drivable till u get it running nice.. then start increasing..
even a fairly worked engine will only use the 3.5 ventury.
Keep the choke under 36..
the bigger the choke the more air and bog you'll get..

what I have again...


Triple webber 45's on a cannon manifold running:

Venturi 36mm
Aux Venturi 4.50mm
Main Jet 145mm
Air corrector Jet 155mm
Emulsion Tube F16
Idle Jet .55mm
Pump Jet .45mm
Needle Valve 2.00mm
Float measurement 12mm
Pump Exhaust Valve 40mm


Carb number 19600.060 Google that number and the parts list popped up.

_________________


Also Known As Clayton Pace

ok..
straight up.. your air correction jet should be close to 60 more than your fuel..
eg.. fuel 145 Air 190 - 200..

there r very few circumstances where this is not so...

it doesnt have to be exactly 60 but this is the general way that webbers are set up...

for your mixture to be perfect the mixture screw should be NO MORE than 1 turn out.
set it to 3 quarter turns out. if you move the screw half a turn in any direction the engine should start to misbehave.. if it does nothing then your mixture is incorrect...

First thing you should do is increase your air jet..
A really worked engine will run fine on 140 fuels..

also reduce your auxiliary ventury.. 3.5 is good for Z's.. 4.5 is getting boarder line...

remember that theres no gains in horsepower to be made from carbies..

i've got a webber hand book so i'll try do some research on why your getting the part throttle problem...

if your running a 36 choke then you will need this at least:

- extractors / exhaust
- cam grind. at least 35/75 or stage 3.
- high compression. at least 9.5 - 1

The choke size is crucial. the bigger the choke the more top end but more bog down low..
A small choke will give you good low rpm response but little top end...
Smaller chokes allow the air to move faster through your carby..
larger chokes makes the air slower at low rpm..

you can only get the benefits of large chokes at high rpm...

so if you want to drive it daily without much effort then keep the chokes smaller...

You know, just listening to you guys, this is all beginning to make sense to me.

The Webers are highly touted as performance carbs because they have several concentric venturis (rather than one venturi, like an American car would have). The smaller venturi responds to low speeds/low air flow, while the larger ones respond to higher speeds/faster air flow. Therefor, the carbs can offer very good performance at nearly any engine speed or airflow conditions. A single or double venturi carburettor would have to compromise by offering its best performance only in a narrow band of engine speed/airflow speed, and the other speeds would have less-than-optimum performance.

The American 4-barrel carbs tried to serve both low speed and hi speed by offering two small throats (each with little venturi) for low speeds, and two huge throats (with BIG venturi) for high speed/hi airflow performance.

I guess the secret part about the Webers is finding the right SIZE jets, venturi, choke (and all the other hard-to-remember items a Weber has on it), to fit your engine size. On top of that, it sounds like each carb HAS to be doing the exact same thing the other two are, at exactly the same time. Six throats feeding six cylinders ~ the tuning must be really demanding.

NOT SURE I AGREE with Pete's statement that there is no horsepower to be gained with carbies. If you consider the engine as nothing more than an airpump, the more air you can allow (or force) into it, the more efficient it will become, and the more power it puts out. That's all multiple carbs do for an engine ~ just allow more air in. Superchargers, turbochargers and blowers (yep~ each is technically different) simply force air down an engine's throat to make more power. The amount of FUEL the engine gets has never been a problem ~ we could invent some sort of fire-hose injector system to dump raw fuel into it by the bucketful if we wanted to. But it wouldn't run then, because the fuel has to be atomiZed in a combustible air/fuel mixture (usually about 12 parts air to 1 part fuel for gasoline). Multiple carbs allow more air in, and develop more ponies (or kangaroos! )

yeah true.. you gotta force it in to get gains...
most cars are fitted with carbies that suit its capacity...
N/A webbers sizes are still governed by an engines capacity..
Theres a formular for working out the basic ventury / choke size for the capacity of each cylinder...
eg. L series 2400 divide 6 cylinders = 400cc

so all in all theres only so much you can get in there without help.
smaller chokes make air flow increased but once you get going doesnt allow high flow...
Large chokes decreases air flow at low rpm.. untill you get going and allow a higher top end at the expense of low driveablity...
Then,....
you have to mix the right amount of fuel at the right time...

its a tricky beast... and very hard to get info about setting them correctly.
even though they were the carby of choice for every racing on the planet

but.. anyone putting 3 carbies on a car is asking for trouble
bloody JAguar V12 has 4 carbies.. YIKES.. 2 SU's on each side
no thanx

Picture yrslf tuning a v12 Ferarri, Maser or Lambo with SIX twin-throat Webers!:shock:

A bloke could go mad!

heheheh.. tuning aint a problemm....
its getting all the carbies to work insync and together...
try disconnecting one carb on the Z twin carb set up and see how it runs..
hehhehehehehe...

the carbies themselves wont go out of tune.. maybe a bit of wear and tear here and there but thats to be expected...
its getting the linkage set=up correct thats crucial...

Thats why a single carby is trouble free.. if its goes abit out of tune just clean the throats and off ya go again...
but no single carby is gonna out perform multi's..

Air,
This is what I run in my car, 74 260 with stock Cam, and header with free flow exhaust.
40 dcoe Canon intake with there crappy linkage.
Main venture-30
Aux venture-45
Main jet-125
Air correction-170
Emulsion tube-F11
Idle jet-50 F9, but I will have to check this with a pin gage as I might have drilled this.
I will also check pump jet, and pump exhaust as soon as possible.

But I would listen to Pete… reading back through my Weber books it would seam that your Chokes are a bit large unless you are looking for more top end performance. I guess one should ask what you are going to do with this car.

I would also like to say Pete…. The last thing you had to worry about was the four Stromberg carbs on a Jag… more like the ignition module or the cap blowing off the distributor because the engine would vent there.

I think I'll just order a whole crap load of jets, chokes, and other parts....



I was building it for autocross, drifting, and spurts of DD'ing,....but after a few times around the block...it's an autocross car now....or feels like it when the carbs can pull it. The 4.11 diff is the speed limiter.... But the exhaust will limit me to what events I can drive in....

_________________


Also Known As Clayton Pace

Hi Air, another bit of info for you..............
you need to run a 3.5 aux venturie if you are running a larger choke, thats a must.
leaner mixture will give more power, 32 choke is a good start.
smaller choke will give better pic up down low, I think the Lambo V12 that has 6 45mm webers runs 32 chokes,
Petes on the button with the fuel block, carbs need to have same pressure,Z I ran with webers ,I used the standard 240Z fuel pump, no problems
make sure all the carbs are connected so they all "bounce" together, a back plate off a skyline GTB weber air cleaner setup is perfect, this will also "calm" the air around the velocity stacks,you are running stack? right? an air box is good BUT make sure you have alot of space inside it, I ran a GTB set up but with the cover on, the back weber suffered badly.
remember you dont win races by having a car that will do 160mph, you win by your car having the ability to accelerate, leaner carbs, smaller chokes, milder cam, $2 of fuel in the tank not a full tank, spare tyre out of the car to make it lighter, these will help, try a 5.8diff..........
when you get it right webers sound sweet, crisp
if not right they will sound like the choke is on, blubbers, not to mention the fuel cost
cheers