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MG MGB Technical - HIF4 Float Setting

Thought I had an earlier problem fixed (rear float full of gas), but first excursion this spring pointed to a continued problem - when the engine is warm.
I finally got around to replacing the second float (it turned out to be filled with gas, too), and have re-installed the carbs, but they are still floading. My shop manual says that the float "gap" setting should be between .020 and .060 inches. I was pretty careful with the setting, but opted for the low end of the range (about .025). Since they are now both still floading badly, I would guess that the setting is not correct.
Is it better to go for the higher end of the range?
HIF-4s are on a 73 BGT. fuel pump pressure has been checked, carbs cleaned, and new needles/seats installed.
Any help greatly appreciated,
Pat
Patrick Callan

Pat, What is the fuel pressure? Are you using Grose Jets for the floats? The ones with the big balls as used in HS carbs will bind if used in HIF carbs. The shop manual says .02" to .04" for float setting. Anywhere in that range should be good. You may want to disable the fuel pump and run the carbs dry. Enable the fuel pump and turn on the igniton, if there is some trash in the valves the sudden fuel rush to fill the empty carbs may clear them. Good luck, Clifton
Clifton Gordon

Clifton,
Fuel pressure is 1.5 psi, am not using Grose Jets. Not sure why they would flood going from a dry condition, unless something was stuck, or the floats just aren't set right. I tried very had to set them at .025", which is within the correct range, so I'm not sure what to try next - will probably take the carbs back off, and re-check everything.
Thanks for the info,
Pat
Patrick Callan

Pat, It sounds like you have everything in order. Perhaps you will find some trash in the fuel. Good Luck, Clifton
Clifton Gordon

Patrick, FWIW, i have been told that HIF carbs are notorious for the floats hanging up when the carbs are removed/replaced. You should be very careful in this operation, trying to hold/bench them in the same horizontal position. You might try wacking the lower body with a screw driver handle to dislodge a hung up float. It is also possible, though not simple, to remove the bottom plates, and check with your finger that the floats are not stuck, after refitting.
I am always ready to be wrong, but I think there are HS4 carbs, and HIF carbs, not HIF4 carbs. You do have the stock 1973 carbs, right- HIF, with internal/integral floatand bowl, right?
Ken R
Ken Rich

Patrick - It sounds very much like the float drop is excessive. If I remember correctly, the 0.020 - 0.060 inch setting is with the float sitting on the needle valve when it is closed (it has been some time since I worked on a set of HIF carbs). What is not addressed is how far the floats will drop when there is no fuel in the chamber. If the drop is excessive, the needle in the needle valve will jam against the float lever and keep the float from rising as gas comes into chamber. I forget how the float drop is set, but this is something that should be checked since your trouble seems to manifest itself when the chambers start out dry. Good luck - Dave
David DuBois

Anyone know if the HIF 44 used on the MGB and the version on the MG Metro Turbo are basically the same ? (Other than needles and Dashpot springs of course)
I am doing a little conversion to my 1968 1275 midget
blake

Thanks all for the additional info. I removed the carbs again, and re-checked the float setting. It was close, but I tried to be even more "exact." Also noted that the carb piston was locked - could have been from a dislodged piece of crud during the clean, because they were free when I originally took them off. So, could have been a combination problem. We will see when I get everything back together and adjusted again.
Ken, believe they are actually HIF-4 carbs. There are also HS-4, but I think most of the U.S. '73s had the HIF-4. Anyway, they are definitely HIF types- no external float chamber.
Seems like a very tricky adjustment, for something that has such critical specs. Hope it's set right this time.
Thanks again,
Pat
Patrick Callan

This thread was discussed between 09/06/2003 and 13/06/2003

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