MGB GT HIF Carb problems

[Huxley Pig]

Hi guys new to the site as just got my first MG (1977 BGT )

Just picked up the car. Drove home in the howling wind and pouring rain. Pulled into the garage and heard dripping. Looked below to find fuel pouring out below.

Realised it was overflow lines. Car had been stood for a while so stripped the carbs and replaced float needles. Did an air test on replacement and appeared to be sealing. Visual checks on floats showed no damage and sank in fuel with no signs of taking in fuel. No signs of floats sticking moving free and easy. Rebuilt carbs but no change to symptoms. Stripped down again and ran through it all again this time checking gaps on floats and adjusted where necessary. Rebuilt with no change to symptoms. Switched on ignition without starting engine. Sure enough pouring out as fuel pump ran. Blocked off overflow pipe. Checked with previous owner who said had no fuel leak issues and had not changed the fuel pump as I was concerned he may have fitted a pump with high PSI and visually does not look to be new pump.

I am now feeling a little confused and am looking for ideas or similar experiences

Thanks

[GreenV8S]

If the carb looks OK, excessive fuel pressure would be the next thing to check. Are you equipped to measure it?

ETA that type of system would have a dead end fuel system with a pressure regulator between the pump and the carb. If the FPR isn't sealing, it'll pass full pump pressure through.

Edited by GreenV8S on Monday 25th March 20:43

[mywifeshusband]

If you're confident the float needles seal correctly and the floats are at the right height, a filter with pressure regulator between the pump and carbs would be my next step. Maybe with a pressure gauge in the line after the filter. 2-3 psi would be plenty to feed the carbs.

https://www.demon-tweeks.com/uk/malpassi-filter-ki...

[wildoliver]

When you say the floats sank in fuel?

Assuming it's a standard su pump then check what the gph rating is for it (I used to know off the top of my head, but ask if you can't find it) stick the fuel pipe to the carbs in to a bottle and measure how long it takes to fill a 2l bottle then work out if it's the right pump. But it will be the first time an su pump has provided more fuel than it should (usually the bloody things pack up and don't deliver at all).

I suspect either float level (or non floaty floats) or the valve isn't sealing at all. I assume the link pipe between carbs has been replaced? These go hard and leak from micro cracks.

[Auntieroll]

To test floats for leakage immerse them in hot water , if a stream of bubbles appears.........
OP did you replace the needle valve seats when you did the needles?
As suggested above the link pipe is another possibility.
If there is any crud in the needle seats as this could cause the same flooding/ overflow symptoms.
If the needles are seating properly and all the float heights etc are correct then start looking for the unusual , excess fuel pressure is ,as mentioned above , highly unlikely to be the cause, far more likely to be something simple .