Interesting discovery on the carbs today

So keep in mind that the Bugeye was one of the first LBCs I bought when was just learning what a wrench was, so forgive my only finding this stuff now....

But I was tuning the Bugeye and quickly realized that the carb mixture were off. I ended up with the carbs having very different mixture settings to get the mixture right. And that seemed odd. So I pulled the bowl tops and discovered that one of the carbs had a conventional needle and one had a Grosse jet. The Grosse jet was the one running way rich.

I'm going to put on a set I rebuilt where everything matches but just for grins is it typical that the Grose jets tend to run rich?

I'm not familiar with those aftermarket float valves, so can't comment. If a float valve allows the float chamber to run "high" with fuel, this will certainly cause a rich condition.
HS2 carbs (1098 and 1275) do not really have adjustable floats so the float chamber level is usually OK if stock float valves are used (you can shim them, but that's rarely needed).

Do your carbs have those "lift buttons" for the pistons? If so, it's a decent way to get idle mixture close.

And, you may already know this, but a general rule-of-thumb for these carbs is: turn the main jets all the way in (UP) and then unscrew two full turns (some books say unscrew "12 flats" because the jets are hex shaped on outer edge). This will get you close.

GROSS(E) jets are evil and WRONG. A set of Viton tipped needle/seat is the best way to go.

Those "two balls do the trick" things are in the same category as purple motor oil, those dial-a-pressure fuel "pressure regulators" and muffler bearings, IMO. Just stuff to take your money, and sometimes VERY disappointing results.

The later grose jets are junk, just put a vition tip needle and seat in the other carb and you should be good to go, it might take you 5 minutes. As for setting float level , you use shims for the all plastic floats, and the early carbs has a metal tang float so you could just bend the tang to correct float level, they are now making a new metal tang float, Joe Curto has them as well as the vition tipped needle and seat valves, and the shim used for the all plastic float. hope this helps.

I will say this though, the type needle and seat valve you are running probably has nothing to do with your carb running rich, check your needle to ake sure both carbs have the same neelde and the jet height is the same on them, putting on another set of carbs just open another can of worms, with a couple of changes you can fix this set of carbs.

Yes, Hap's right. Joe Curto is the guy to call if you need SU parts.

https://www.joecurto.com/

+2 on Grose jets. I removed them from my LBCs and only fit the Viton tipped valves now.

Thanks guys - appreciate all the info. Always good to learn something.

Hap - seems obvious now but it didn't occur to me that the needles are probably mismatched. Would not be a surprise given the Grose jet thing - duh! :laugh:

I've never dealt with a mismatched set of carbs like this so it was a bit eye opening how much of an impact the Grose jet and/or needles seemed to have. I have the mixture and float levels OK enough now, and balanced the carbs, and she starts easily and runs. it is just that settings I had to use to do that are kinda goofy so clearly not all is well with these carbs.

I have a set of rebuilt/rebushed HS2 with the correct Viton needle that I'll be putting on in the next couple of days so to some extent this is a bit academic but interesting stuff to learn.

As a side note - this is the strongest 1098 Ive ever experienced, I'd not go quite so far as to say she is fast but she's quick. Even with the carb issues she picks herself up and goes! Much fun.

Thanks again for the info, and I'll report back once I get the healthy carbs on her.

The jets can get worn or damaged too. Remember, you're dealing with dimensions that have to be held to something like 0.0001" so it doesn't take much to mess things up. New jets and needles aren't expensive.

By the way, when I say "jets" I mean the part with the hole that the needle goes into. Calling a float valve a "jet," as in "Grose jets" is a bit of a misnomer.

Good point Steve, the carbs could easily have wildly different wear patterns before they ended up on this car.

Ok, clearly there are strong anti grosse jet opinions. Can I ask why? specifically? what do they or don't they do? Thanks

JP, the silly things are HIGHLY subject to vibration, for one. Bounce on the seats and flood. Not good.

Hap may have a more thorough explanation, but I'll just say the things are unreliable junk. Period.

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I miss Billy Mays. :frown:

DrEntropy said:

JP, the silly things are HIGHLY subject to vibration, for one. Bounce on the seats and flood. Not good.

Hap may have a more thorough explanation, but I'll just say the things are unreliable junk. Period.

Click to expand...

Bump - Hap can you add to this discussion?

thanks

Until Hap posts....

I had Grose Jets in both the Mini and our GT6. On one they stuck closed, on the other they never properly shut off creating fuel starvation on one and flooding on the other.

The hearsay is that the original Grose Jet was produced by a family business and now it is made by a conglomerate with a lack of quality control. Whether that is true or not is highly subjective. One thing that is pretty well documented is that the "new" Grose Jet product is shipped with a Cosmoline like coating inside, presumably to keep the ball bearings from corroding in storage. There are reports that if you do not wash that coating off with carb cleaner or another strong solvent you will have problems with the Grose Jets.

Regardless of what is true or false you will find this community divided on the subject. People either love them or hate them. After having problems on two cars I simply don't use Grose Jets anymore.

I simply use fuel without corn oil. No probs since I switched.