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MG MGB Technical - HIF float

First time I have seen this in forty plus years of working on SU carbs!

Plastic float half full of fuel - no sign of a hole and it doesn't leak out when I warm the float (no naked flames!!)

Anyone seen this happen?


Chris at Octarine Services

Yep--had it happen to my mate's MGA hotty at the historic meeting last year,(1st time also) bit rare and could have been like it for a while as the mixture on that carb had been gradually wound up to compensate for it but eventually it started flooding up at idle and wouldn't clear , something i hadn't really noticed before that they were handed as well,have always just poked them back in where they came from and pure luck never got them mixed up i guess
William Revit

Yes, on my V8. Couldn't see the fuel there but could hear it. Like you heating and squeezing didn't reveal the leak.

Incidentally I saw someone had a new 'stay up' float sink. They returned it to the supplier who said "You must have damaged it".
paulh4

It was on my V8 - must be a V8 thing!
Chris at Octarine Services

Them stay up floats are a pain in the but-
They only have to get a little scratch on them and the fuel weeps in and down they go
The smooth surface is the only seal they have
Lots of Japanese cars here had them--Lots of Japanese cars here had issues with them--
Luckily a lot of Jap cars had a glass window on the floatbowl so you could look in and see it sitting on the bottom


William Revit

Same here............V8. But this was a newish float. The old ones went back in and haven't been an issue.
There is a lot of heat from the block, which may contribute to float breakdown, I put a slab of insulation under the float chambers.


Allan Reeling

"Once is happen-stance, twice is coincidence, three times is enemy action, Mr Bond".

I suspect that one is as much poor manufacturing as anything else, mine was probably even darker than Chris's. I've only had the one fail in 100k, even though often in summer the float chamber gets hot enough to boil the fuel out of them, I can hear it.
paulh4

I notice that the two pictured are from left hand carbs - was yours Paul?
Chris at Octarine Services

The float that died on the MGA was on the front carb, how that relates to L/R on a v8 I'm not sure but I think Left as the idle mixture screw is on the front
William Revit

My float failed a couple of years ago HIF fitted 2005 4 pot supercharged
Michael Beswick

I've not had a failure on our '74 B/GT with the HIF floats in my over thirty years ownership. I have done a full cleaning and re-build (new floats and gaskets) about every ten years. Plenty of discoloration of the plastic (like Chris) but no fuel leakage (so far).

Have me thinking it's about due again though.... ;-)

Larry C.
LC

With the quality of stuff these days I really don't think routine replacement of stuff like that is a good idea. It's bad enough when you do have to start replacing things, then have to again and again, like wheel cylinders, clutch slaves, heater taps, hoses, and so on.

I've had the roadster 30 years I only changed the bottom hose a couple of years ago when I had the radiator out, and seriously debated whether to put it back. It was still black, shiny and supple. Top and heater hoses on that and top and bottom hoses on the V8 have been replaced a couple of times.

Same with the V8 fuel pump hoses, I only replaced those because they were almost certainly original and the braiding was crumbling away. I slit a piece lengthwise and opened it out, and it was perfect, no sign of deterioration at all.
paulh4

Paul,

Thanks for the advise. I will delay the next re-build on the HIF's for now, and also kept the previous ones which were only dis-colored from use and age for spares.

Regards,

Larry C.
LC

This thread was discussed between 07/01/2020 and 14/01/2020

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