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MG MGB Technical - Fuel Pressure Reduction Unit

Hi,
Can anyone recommend an inline fuel pressure reduction unit for a '71 MGB. I understand the fuel pressure reading should be around 1½ lbs, whereas mine is close to 5lb at the inline filter.
Thanks
Ken
Ken Martin

The Filterking works well and is easily adjustable. Its available as a simple pressure regulator or as a combined regulator and filter with a glass sight bowl which is the better of the two. I"ve used them for years, mostly on cars fitted with Webers Or Dellorto"s and they have been extremely reliable and effective. Moss in the U.K. carry stock so pressumably they are available on your side of the pond.
jim soutar

Hi Jim,
They are not listed in the Moss Catalogue, so I guess I'll just keep on looking, Thanks anyway.
Ken
Ken Martin

Ken - You need 2.7psi to your carbs. I.5 psi might work but it is a bit on the low side. Cheers - Dave
David DuBois

Ken, I think your 5psi pump pressure is fine and you don't need a pressure reducer. Barc
Barc Cunningham

Hi Guys
This is all part of the problem I had with the fuel flow a while back, which suddenly disappeard following a reverse tow (back end in the air) to a garage. The car suddenly ran like a scalded cat. I thought that maybe there was something in the tank that had rolled away from the pick-up tube during the tow. So I drained the gas and dropped the tank but it was completely clean. I also installed a fuel pressure gauge at the time which showed between 4-5 lbs on tick over, could be more on the road. I was down at the garage yesterday and the mechanic squeezed the line into the carb as much as he could and the engine kept running. In fact the revs increased slightly. So he said the pressure should be 1.5 lbs. If you figure 2.7 Dave, I'll go for anything under 3. But I still need to find a supplier of a reduction valve.
Thanks
Ken
Ken Martin

"the mechanic squeezed the line into the carb as much as he could and the engine kept running. In fact the revs increased slightly"

How long for? Takes a while for the float chambers to empty when the engine is warm and idling once the fuel supply has been cut off.
Paul Hunt

Hi Paul,

He squeezed for probably 3-4 minutes.
Based on an artical I was just reading on SU pumps, Dave DuBois is right on the nail with 2.7lbs, thanks Dave.
I was also reading a past thread (5/23/09) on fuel leaking from a carburator which included a section from Frank Grimaldi who seems to have had a problem with very similar symptoms as mine and which a regulator cured. So I have just ordered one up from Mr. Gasket over here which is adjustable from 1 - 6 lbs and I'll let you know if it works.
Thanks
Ken
Ken Martin

I suggest a Mr. Gasket Adjustable Fuel Pressure regulator. Mine works best with the pressure setting at 3 PSI. They are priced about $25 and are available most place including eBay.
Frank Grimaldi

Ken - What kind of a fuel pump do you have on your car? The SU fuel pumps only puts out 2.7 or 3.8 psi, either of which works fine on MGBs. Because the SU, Facet and many other type of pumps are impulse pumps, it is very difficult to get an accurate reading of the actual pressure at the carburetors (on my test site, I take the average of the high and low reading for each impulse). If you have a vane type of pump, such as Holly or Carter, you might be ahead of the game to go back to the OEM SU pump. Cheers - Dave
David DuBois

David - I would have thought that once the float chambers were full (ignition on engine not running) and the pump is only clicking once every 30 secs or less pressure would have been stable enough to read?
Paul Hunt

Hi Guys
I finally fitted a fuel pressure regulator and managed to get the fuel pressure down to 2.75 lbs, or as near as I can to it and she seems to be running quite a bit smoother. The only thing I have now found is a little bit of a ping on acceleration, which brings me to the question. My engine is an 18GK.........., or so it says on the plate. Now according to the Haynes manual the timing should be 14 deg BTDC at 600 RPM. However there are only 3 notches on the pulley as per fig 4.9, each with a spacing of 5 deg. 3 teeth equals 2 spaces x 5 deg each = 10 deg. How the hell do I get 14 deg? Any ideas?
Ken

Ken Martin

This thread was discussed between 22/05/2009 and 13/06/2009

MG MGB Technical index

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