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MG MGB Technical - Grose jets-flooding

Since fitting grose jets on my HS4 float chamber covers Iíve been experiencing a misfire due to flooding. On examination it seems fuel is leaking past the threads of the jets despite washers being fitted.
Iíve thought about using a thread locking compound, but which one is suitable to use with fuel? Has anyone else found a fix for this fire risk?
J Hughes

Scarap the new Grose Jets. They appear to be nothing like the original ones. Use Viton tipped float needles and your problems will be gone.

'Grose'ly deficient.
Paul Hunt

Back in the '90s, they were a great product, but they were bought out by a company that didn't care very much about quality control. Today, they are to be avoided. Go with the Viton tipped needles as recommended above. RAY
rjm RAY

I agree with the above. But if you want to persevere with what you have, Loctite 243 has been a successful sealant/locker in the screws that hold on the fuel tank sender in my custom fuel tank for the last 25 years in which the screw holes were drilled and tapped through the side. Even with 10% ethanol.
Paul Walbran

I was having trouble with periodic fuel overflow for the past couple of years. I was running old Grose jets(made by the original owner).

My float bowl covers had cracked spindle holes and the nylon floats were looking old. So I bought new flow bowl cover assemblies from Moss and used the supplied viton tipped jets.

No more overflows. I think the Grose jets weren't always seating properly at times. Add to that floats that had wear where the jet rests on the float tang.

Robert McCoy

Thanks for all the input guys; yes it is the Grose jets in-fact both are faulty. With the floats removed and an airline connected to the input on the lid and a finger holding the valve closed I dunked the lid into a tub of water. Bubbles appeared both from the threads and body at just over 2psi. I then tested a 20+year old needle type valve no bubbles appeared even at 18psi.
2 new viton tipped jets should arrive tomorrow with luck.
J Hughes


I fitted the new viton tipped jets and ran the previous tests. The front float chamber was perfect but the rear still leaked at anything above 3psi.
On closer examination the needle valve it self was not the problem this time, but the seating. To cut a long story short Iíve been running the car for several weeks on test (hence the delay with this update) with an original SU needle and jet without an issue. However at the first opportunity Iíll replace the lid.
J Hughes

Viton tipped needle & seats, unbeatable. You can get them from Joe Curto in the USA.

F. Camilleri

This thread was discussed between 29/06/2015 and 28/07/2015

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