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MG MGB Technical - Grose or not?

1973 MGB, SU-HIF with a float valve that does not close all of the time. I have to go in anyway, are Grose jets the way to go? Tom
Tom

The Grose jets that are being made today are crap. Use the Viton-tipped needles from Burlen Fuel Systems. Click on this- http://www.burlen.co.uk/
Steve S.

The carb bottoms are off and the floats don't have any gas in them. There is a lot of "play" between the float and the "axle-pin." There are already viton tipped valves in both carbs. Both "flappers" that engage the valve have small indents worn into them. Could this be the cause of my flooding? Also, the "O" ring from Moss is square and the installed ones are circular. Are both OK? Thanks, Tom
Tom

Hi Tom

The O rings are square in the Kits. Reset the float height, see what happens. The viton tips usually do the trick and flooding tends to be caused by debris in/around the flow jets.

Peter
peter burgess

You may want to try reducing your fuel pressure.

A fellow club member had problems with his carbs overflowing, until he installed a fuel pressure regulator.
BE Clough

I'm having the same problem guys! Today I pulled my 73-74 B out of storage in the basement and put the TR6 in it's place for now. I wanted to start the B and see how it is doing after sitting for two years.
I put in new gas and hooked up the battery and it ran fine for about a minute, then the back carb started leaking out the overflow. I took off the float top and cleaned the chamber and needle seat four times. It seemed to work fine every time I would put it back together, but it still leaks. I also checked the float pin and it has little grooves in it where the flow hinge moves. Is this normal or worn?
There are no adjustments on the float. It's just solid plastic, so I can't adjust anything.
As a side note, last year, while it was sitting I replaced the fuel pump with a none original SS pump. It seems like I shouldn't have to put a regulator on it, or should I???
Cleve

Non-SU pumps often need a regulator as they frequently put out too much pressure. If you get overflow with an SU it is the carbs that are the problem. Anything in the float pivot or linkages that has grooves or notches from wear could cause it to stick. Gum from fuel evaporation after not been used for some time can cause floats to stick or not close fully. Disconnecting the pump (white wires in the mass by the fusebox where the main harness joins the rear, or simply disconnecting the fuse that it is very wise to have), running the carbs dry then reconnecting the pump can often flush any debris out of the now wide-open valves. If it happens again check the float very carefully, sometimes fuel inside it is not obvious. After that if new valves don't help it's time to look at dirty fuel. Float height in itself won't cause flooding, unless it is so badly set that it can't rise high enough to push the valve fully into its seat. Whilst that could happen after work it is highly unlikely after simply not being used for a while.
Paul Hunt

Paul,
Thanks for that! I noticed last evening while looking through a parts book that I have carbs from an earlier car, not from the 1973-74. (I have to write it like that because I am not sure what year it is yet)
I'm going to purchase some brass rod and make a new axle for the float and see if that helps. If not, I'll purchase a regulator. Thanks again!
Cleve

I took the float apart one more time and it still leaks, so I bought a pressure regulator. It’s adjustable from 1-6 psi, so I thought I would try it on 3 psi and see how that does.
Does anyone know where the best location would be to mount the regulator? Near the pump or near the carbs?
Cleve

Hi Cleve, under the bonnet where you can see it.SUs are happy on 1 1/2 -2psi, the old filter king regulators don't like dropping down that low and are ready to fly apart at low settings. The best ones are the ones with a dial on top with numbers representing pressure.

Don't forget the old trick of a thin washer under the brass flo-jet, this also lowers the float height.

The HIF carb float height is adjustable.

Peter
peter burgess

I had a similar problem on the rear HS4 carb on my car. The taper jet is in good condition and it didn't appear to be sticking. The fuel pump had recently been changed for an electronic SU unit so I too initially suspected there was too much pressure, but as it is specifically specified as being suitable for the B I discounted this until I had explorer all other options. I also considered fitting Grose valves but a little bit on Internet research (non-MG specific) reported that these often didn't cure the problem and there were concerns about the quality of units currently being sold.

On a whim, I fitted a O ring seal between the taper-valve and the carb body as Peter's suggestion above and thus far it seems to have resolved the problem.

I plan to overhaul the carbs over the summer, but because the car has only done 28k miles since new I'll just be cleaning and fitting a new SU seal & gasket kit.
Mike

I had a fuel leaking problem and solved it with new standard float valves and 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

Just a follow up from last week.
I purchased a pressure regulator and installed it this weekend and drove the car around. No more flooding, so I guess it wasn't the needle and seat.
Thanks for all the input!
Cleve

Just an update on the '73B flooding issue. I replaced the floats, floar spindles, viton tipped float vales and thier seats. About 25 miles and 8 off/on cycles. So far, so good. Both the floats & the spindles were fairly worn with lots od free play.
regards, Tom
Tom

This thread was discussed between 22/05/2009 and 31/05/2009

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