Saw this referred to over in the Help Me! forum. Didn't seem to be relevant to the thread and I have no emergency so I thought I'd ask here:

What is a Grose Jet? And why is it apparently a better choice than a needle valve for carbs?

Chris

The Grose Jet is a replacement for the float chamber needle valve. They had a better valve design and were less prone to failure.

They are no longer available for our Datsun-licensed SU carbs.

They were a simple two ball design. The float lever rose contacting a larger ball which in turn raised a smaller ball which shut the orifice. That's fancy speak for the "hole" through which the petrol comes a gushing......

Back when I was doing my MG, (early '90s), they were quite common in the Brit-car world. But even back then, they were a "love 'em or hate 'em" thing. Lots of people swore they were awesome, but numerous people blamed them for failures up to and including engine fires from overflowing float bowls.

I honestly can't remember if I had Grose jets in the MG or not. In an odd coincidence, I did just replace the float needles and seat in the Datsun carbs just last week.

One of the first things we found after taking over the company was that 4 cylinder motors set up a harmonic at about 3 grand that literally rattled them open which would certainly lead to the overfill siuation and potential combustious maximus situation....

Old Scott did a fair country job of overselling the hell out of Grose Jets.

Thanks all for the replies.

I think I can see where the "love em or hate em" aspect comes from. The design of the Grose Jets appears more resistant to clogging / jamming from debris or build-up, and possibly allow for a finer and more controlled flow of fuel into the chamber. But, man, trying to figure out an over-rich (or flaming!) condition that comes on at speed -- wheeew, that could produce an inventive vocabulary landing you one circle deeper in Hades.

Chris