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MG MGB Technical - SU carburetor needle question

I have a 1974 and a half MGB that I am swapping carburetors on. I am taking off the Zenith and attempting to put on a SU HIF6, AUD 584 carb. The setup is the original intake/exhaust manifold, one barb set-up. It idles fine, but seems to starve on acceleration once it hits 3000 RPM. I am thinking the needle is incorrect, but would appreciate any info anyone has. The HIF6 was taken apart and cleaned and adjusted over the winter, but not professionally. I see the MGB application of the HIF carburetor is an HIF4, with AUD of 493, 550, and 630 I believe. Could the needle be the issue? and will the HIF4 needle fit a HIF6 carb?
Russell

You sure your fuel pump is up to scratch? I wouldnt have thought the HIF4 needle would work right for the HIF6 carb at all. I might be (and probably am) wrong there but its just a thought!
Ross Kelly

Ross:
I do believe the fuel pump is good, as the car runs good when the Zenith is on it, just overly rich, as I am sure you know is common with the Zenith. I have not swapped out the needle from the HIF6, so I am presuming it is indeed the original HIF6, AUD 584 spec, which was used on 1972-1974 Austin Marina 1.8 liter engines. I also am not sure if the HIF4 needle used in MGB applications will work properly in an HIF 6 carb. The other thought I have is whether the single HIF 6 carb is sufficient for the MGB, or if I am asking it to do more than it was designed to do.
Russell

Russel,

you did not quote the source/car your carb came from.
Moss US and Anglo Parts offer such kits and they come with different needles and damper springs.
The needles from a HIF4 will not fit, there is an other jet size in the HIF6!
May be you should try a weaker spring first. A red or light blue coded one will help the piston to move faster and furter upwards.

Hope this helps

Ralph
Ralph

Hi Ralph:

The carb came used from a man who was running it on an MGB, and he claimed no issues with it. I actually bought it to get the manifold, but was intrigued by using it instead of the Zenith, which I do not particularly like. The AUD tag indicates it was spec'd for a 1972-1974 Austin marina, US market, 1.8 liter engine, so it would appear to be a good match for the MGB 1.8 liter. I appreciate the info regarding Moss, as well as the incompatibility of the HIF4 and HIF6 needles. Perhaps Moss will have a richer needle for the HIF6.
Russell

Russell,

when it came from a Marina, i would first try the Marina ignition setting before modifying the carb.

Ralph
Ralph

For needles and carb info call Joe Curto, the numbers on his web site.
John H

This thread was discussed between 18/06/2008 and 19/06/2008

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