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MG MGB Technical - SU HIF4 main jet colour

Yesterday I took the bottom off the float chambers on both of my HIF4 carbs. I wanted to change the float chamber needle valves while they are off the car.

Looking inside the float chambers I noticed that on one carb the main jet tube was off white and on the other the main jet tube was black. Are the colours of any significance? eg different sizes of jet.

Thanks

David
David Witham

While I am on the subject of SU HIF4 carbs, I am planning to fit new spindles and bush the bodies. I have read about people machining the bodies of SU carbs to take bushes that are available from Burlen.

On examining the carb bodies I find there are already bushes fitted. Were these original on the HIF4? If so are the new bushes the same OD meaning that I only need to get the old bush out and don't need to worry about machining or reaming the hole.
David Witham

The difference in color is correct. One is for the front carb and the other is for the rear. The difference is in how the elbow at the bottom is formed and pointing
Gerry

Try the new shafts in the old bushes first - it is rare that bushes are so worn that you will improve things by replacing them. The bushes are cast into the bodies on most carbs, and you still need to machine the hole, and then line ream the bushes after. Takes good tools and good skills. As an example, in my 40 years of doing zillions of these, I have only seen a few "virgins" that actually had to have bushes, but I've seen way more that needed them because the last guy had already replaced them.
FRM
FR Millmore

If your hif-4 have the bushings in them. That means it is a later SU. (around 1974) You can take a piece of round stock and punch them out and replace the bushing with new ones.(don't forget the lock tight on bushings) If they are still on the car spray a little carb cleaner on them. If the engine speeds up the bushing and shaft is leaking and need replacing
John Terschak

Thanks for the comments.

John, I will try pushing the existing bushes out first before risking a drill and or reamer.
David Witham

This thread was discussed between 05/04/2007 and 09/04/2007

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