[Mike]

i all three carbies to choose from but i'm wondering what the pros and cons are of all three
i know about the the angle issues of the weber but i want to know how all three compare onroad?
are there any improvements using a 4k carbie over a standard one?

Cheers
Mike

[Zook_Fan]

I have absolutely no idea how the 4k would go, maybe you should try it

BUT i know that for onroad use the webber would most likely be the best of the other two. I have just recently driven a zook with a weber and i was suprised how little difference there was onroad but it was noticeable. It had slightly better acceleration than mine but offroad mine could shit all over it, because of the prementioned angles but that is another story...

[Laney]

i run 32-36 webber its great and dont really have probs on hill just gota keep fuel up to it and mines runnin lil rich

[nissvit]

The 4K & the sierra carbies are both made by aisian?, the main jets and other bits and pieces are interchangeable.

The size of the 4k throats measure as a little bigger than the sierra version. My guess is the smaller throat size in the sierra gives higher air-speed past the venturi so you get a better mixture and better response/ torque at lower rpm. From memory most of the 4k's had a simple weighted second throat opening, where the sierra run a vacuum operated secondary, so getting the secondary to open at the right time might be difficult.

If you are willing to put up with the sierra carby and spend the time, they run well off road, can't quite get steve's to run upside down yet, but am getting closer .. .


If you going to rip the carby off because you want more go, check these couple of regular probs before throwing it out..

- the lever that pushes open the second throat doesn't touch. straighten the lever with a pair of pliers so it just opens the second butterfly- only needs to open the second throat so you can fit a 2mm drill down the side of the open butterfly, if you can fit a 3mm (1/8") its too big.

- when you unwind all of the idle screws make sure that the two butterflies fully close. Most sierra carbies seem to have butterflies that aren't centered, so the throats never fully close, giving poor idle speed & mixture control. loosen the screws that hold the butterflies, gently move the shafts until the butterfly is centred, (it goes fully closed) then tighten the holding screws again- simple

- Check that the accelerator pump is actually working through the range it is supposed to be working. the factory measurement is 3.2-4mm movement of the accel plunger -Measured at the top of the carby body. I have found this measurement leaves a dead spot at the end of the first throat movement - often felt as a flat spot half way through second gear acceleration.
To adjust this, bend the rod that moves the accelerator arm.
Best results found so far are when the accelerator pump moves the during the entire primary buterfly movement (approx accel pump movement at carby top -5-6mm). Any more accel pump then this, and internally you raise the pump plunger out of the fuel bowl and you may get inconsistent fuel delivery at initial accellerator pedal movement when the car is doing big angles..

- lastly check that the gaskets have holes in them where they should - there is a vaccuum passage that needs to be open on both side of the crescent machined in the sandwich plate to the manifold, with this blocked by gasket, you will get some weird stuff happening.

[Mike]

I am currently running a 32/36 dgav and i am quite happy with it the only reason i'm thinking of changing is the weber has an auto choke and the 4k carbie i have has a manual choke
i would prefer to have a manual choke but i don't want to loose too much performance

[Built4thrashing]

i ran the weber for ages and when it shat itself(worn out shafts) i put a 4k carby on it. its very close to the weber on the road and as good as the sierra carby offroad. They are jetted bigger than the sierra carby and the mechanical secondaries is alot better than the vac setup.

[Mike]

Built4thrashing wrote:

i ran the weber for ages and when it shat itself(worn out shafts) i put a 4k carby on it. its very close to the weber on the road and as good as the sierra carby offroad. They are jetted bigger than the sierra carby and the mechanical secondaries is alot better than the vac setup.

thats exactly what i wanted to hear

[TheFrayne]

Are these ever used on the 1lts? (webber)

[Damo]

nissvit wrote:

The 4K & the sierra carbies are both made by aisian?, the main jets and other bits and pieces are interchangeable.

The size of the 4k throats measure as a little bigger than the sierra version. My guess is the smaller throat size in the sierra gives higher air-speed past the venturi so you get a better mixture and better response/ torque at lower rpm. From memory most of the 4k's had a simple weighted second throat opening, where the sierra run a vacuum operated secondary, so getting the secondary to open at the right time might be difficult.

If you are willing to put up with the sierra carby and spend the time, they run well off road, can't quite get steve's to run upside down yet, but am getting closer .. .


If you going to rip the carby off because you want more go, check these couple of regular probs before throwing it out..

- the lever that pushes open the second throat doesn't touch. straighten the lever with a pair of pliers so it just opens the second butterfly- only needs to open the second throat so you can fit a 2mm drill down the side of the open butterfly, if you can fit a 3mm (1/8") its too big.

- when you unwind all of the idle screws make sure that the two butterflies fully close. Most sierra carbies seem to have butterflies that aren't centered, so the throats never fully close, giving poor idle speed & mixture control. loosen the screws that hold the butterflies, gently move the shafts until the butterfly is centred, (it goes fully closed) then tighten the holding screws again- simple

- Check that the accelerator pump is actually working through the range it is supposed to be working. the factory measurement is 3.2-4mm movement of the accel plunger -Measured at the top of the carby body. I have found this measurement leaves a dead spot at the end of the first throat movement - often felt as a flat spot half way through second gear acceleration.
To adjust this, bend the rod that moves the accelerator arm.
Best results found so far are when the accelerator pump moves the during the entire primary buterfly movement (approx accel pump movement at carby top -5-6mm). Any more accel pump then this, and internally you raise the pump plunger out of the fuel bowl and you may get inconsistent fuel delivery at initial accellerator pedal movement when the car is doing big angles..

- lastly check that the gaskets have holes in them where they should - there is a vaccuum passage that needs to be open on both side of the crescent machined in the sandwich plate to the manifold, with this blocked by gasket, you will get some weird stuff happening.

I don't even run a carb any more but I still appreciate you taking the time to type all that!!!

[jonno_racing]

Mike wrote:

Built4thrashing wrote:

i ran the weber for ages and when it shat itself(worn out shafts) i put a 4k carby on it. its very close to the weber on the road and as good as the sierra carby offroad. They are jetted bigger than the sierra carby and the mechanical secondaries is alot better than the vac setup.

thats exactly what i wanted to hear

well come get this fracking motor and carbi before i send it to sims metals!