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Running some twin hs2s...

The left hand bowl is leaking. The carbs have had a full rebuild kit on them. So had new valves with the rubber tips, and the little brass tubes that came with the kit.

It's leaking out the overflow, I've swapped the float, thinking the one that was in had sprung a leak, I've also swapped the lid and put the new internals in you it, just in case there was a casting issue...

It seemed fine, until I was almost home, and I could smell the petrol again. Opening the bonnet revealed the same problem, overflow leaking...

It's about 10 miles for me from work to home....

The car still runs well


Any clues!?

Ed

A couple of possibilities are;

A little lump of crap is in the valve. Take it off & chck it by blowing down the pipe & operating the valve by hand.

The valve isn't seated quite properly in the float bowl lid allowing fuel to bypass the valve. Unscrew the valve & check it is seated / sealed properly.

Finally, check that the flexible mounting in the carb where the float bowl attaches is not squashed flat the float bowl needs to be mounted flexibly, if it isn't the valve will fail.

What fuel pump are you using?

Too much pressure could cause it.

It's a standard SU pump...

I took it all apart again, cleaned it all and it seems to be ok for now!?

Perhaps it was just a bit of dirt?

Time will tell!!
Ed

If you re-used old rubber fuel hose when re-fitting the carbs, there is always the chance that bits of old rubber found their way into the float valve.

i've had this from time to time on many HS type SUs.
Using the 'viton' tipped needle and seats is a good thing but a sure fix is the 'grose' type ball/valve and seat.
added to this....make absolutely sure the float moves up and down freely but does not wobble about from side to side. Spending time fettling and 'tuning' the little hinge and pin on the float is worthwhile.
an inline filter at the tank exit is a good thing too.

I have had the exact opposite experience with Grose Jets. I have had them stick open and I have had them stick closed. I have removed them from the cars where they were once installed and I now only use Viton tipped needles.

In fairness to the product, I have since been told that new Grose Jets are shipped with a coating applied to the steel balls to prevent them from rusting in storage. I understand that this coating must be removed from the balls prior to using the jet. I was told that the coating can be removed by soaking the jet in carb cleaner and blowing them out with compressed air.