View Full Version : Front Zenith carb overflowing

07-13-2007, 09:23 AM
The front carb on my 73 TR6 is overflowing. Gas is leaking from everywhere. It sone of them Zenith jobbies. I've tightened all the body screws. I got a feeling the float is stuck. Any ideas? Thanks

07-13-2007, 09:35 AM
sounds like you got some crud (technical term) keeping the jet stuck open. I've removed the float bowl without removing the carb for the same problem. You can't really set the float level like that but you can remove the jet for a cleaning or replacement.


07-13-2007, 09:49 AM
I told all of you that it was just a matter of time before Crypty started the infection process stateside.

No one believed me. It was just a rear view mirror you all said. What damage can that thing cause?

Well here we are. The same symptoms starting on a poor innocent bystander in NY. It's like the plague. It jumps from car to car.

If I were you I'd summon Divine help ASAP.

07-13-2007, 09:50 AM
i've got the carb off and the bottom case off. Looks like the prvious owner may have changed the needle to one of those gross ball. Its a brass fitting with a little silver ball at the top. I guess I should remove it and clean it with some carb cleaner. Any thing I should do since the carb is off?

07-13-2007, 09:58 AM
i've got the carb off and the bottom case off. Looks like the prvious owner may have changed the needle to one of those gross ball. Its a brass fitting with a little silver ball at the top. I guess I should remove it and clean it with some carb cleaner. Any thing I should do since the carb is off? IMO, throw the gross thing as far as you can, and put a real needle valve in there.

07-13-2007, 10:36 AM
Make sure the float itself is moving freely and not hanging up. I would want to remove the float and shake it to see if there is any fuel inside the float. That is another issue all in itself.

07-13-2007, 11:19 AM
I have seen the floats installed upside-down. Car had a fuel leak which is why I was able to buy it so cheaply ;-)

07-13-2007, 11:24 AM
Ok I cleaned the Grose Jet and made sure the float wasn't sticking and that the float was air tight. I sprayed every hole I could find with Carb cleaner and then blew everything dry and put the carb back on. Started car and same problem. To much gas is getting in. Any other ideas?

07-13-2007, 12:07 PM

Did you do anything to change your fuel pressure?

New fuel pump, rebuild the old one, etc?
Fuel pressure needs to be under 3 psi.

I too, recommend you go back to the proper design needle and seat.

My experience with Gross jets is that the debris ingested will tarnish/or indent the balls. The principle of fuel shut off is one ball resting against another and when they are minutely affected that seal goes away. So any I come in contact with I advise the owner to replace with viton needle and seats.

07-13-2007, 01:19 PM
I also would change that Grose jet to a conventional viton one.
Be aware that you will need to reset the float height after you have done so because the needle valves have differing heights

07-13-2007, 08:15 PM
Good point, Graham

Guess you didn't pick up on the Gros"s" thing. That's what we called them when they went south. Becam a gross thing.

07-13-2007, 11:30 PM
I just posted on this in the Jag forum (Fuel pouring out top port of carb..)

In my case the float hinge had popped off on one side, the side which contacts the button shut off on the grose jet....

This probably isn't the case it sounds in your situation, but the bottom line is the float is not contacting the jet to push it far enough up as fuel fills the bowl, allowing it to shut off the fuel intake for that carb. The excess is probably also pouring back into your intake into the exhaust. I would bend (adjust) the float to make less clearance distance, this is trial and error. The idea is to make sure the float rises high enough to close the jet. Start with a gradual change, see if possibly you have the factory procedure for your car which would give you a starting point. You probably aren't having the issue on the other carb, so you may measure both float to jet shut distances to see if this may be the case. A backfire with this issue is an engine fire in the making. Leave the air cleaner(s) off while you try to get the float level set properly. Also, I was able to cut down on the fuel pouring initially by adjusting that carb on the car, but of course, not a good fix, just trial and error and my trying to avoid pulling the carbs and checking the floats. Your jet may be bad, but sounds like an adjustment. To test that you could switch the jets, see if the same condition occurs in the other carb..... Hope this helps, and I don't think that Grose jets are too horrible, try the float level adjust before you scrap them. (Maybe swap the jet and float to the other carb, then see what happens... a quick start should tell you right away if you need to replace the jets and floats, test swapping just the jets first though. Also, have you loosened and calibrated the throttle shafts on the carbs? Just a thought, but all of these steps I did corrected the problem and tuned the carbs to work together.)

Brian /bcforum/images/%%GRAEMLIN_URL%%/cheers.gif

07-14-2007, 06:06 AM
I'll chime in here and agree: Bin the "gross" jets. Hateful things. Get the Viton tipped needles, Joe Curto for any/all carb bits.

07-14-2007, 12:33 PM
Ok problem is fixed. I took the carb all apart again and soaked everything. I then blew it out. Put it back together and it no longer overflows. So I'm not sure if the float was stuck or if some dirt got trapped on the jet. Either way its fixed. Thanks guys. One other question. Are the stock jets all that much better than the Grose jets or is it just personal perference?

07-14-2007, 01:01 PM
As long as you keep the fuel flow clean, it doesn't matter.

The classic needle and seat would develop a depression in the needle(early rubbers) that would let fuel slip by, after many moons of driving.

So Gross(e) jets came around. Their principle of operation is by having balls compress, think of having a couple of tennis balls resting atop each other inside a tube. When the fuel drops the balls separate and fuel goes around them in the tube. However when dirt or crud enters the ball holder the problem starts. If it's just superficial crud it can be blown out. But if it's chunk of junk...... It will form depressions in one or two of the balls and you will NEVER obtain that tight ball to ball seal, needed to stop gas flow. Seemed to me the quality of the Gros(e) jets went down around the same time the people of the needle and seats starting improving their product by going to a Viton rubber.
And it is a lot easier to clean out a typical needle and seat than a Grose jet.The Grose's in my cars came out and now I use needle and seats. Any car problems with anyone here and I recommend going to a good viton needle and seat. And ZS/Weber/Hitachi/Dellorto needle and seats are not that rare. A good parts house that carries carburetor stuff for their carburetor shops can get them for you. Or you can try one of the carb specialists listed on this forum. I still recommend BP Northwest as a supplier in your area. If you haven't yet dealt with them, recommend you do so, You will be pleasantly surprised.

07-14-2007, 06:44 PM
Are the stock jets all that much better than the Grose jets or is it just personal perference?
I've never used Grose jets on my cars, but I have fixed persistant overflowing problems for others several times now by swapping the stock needle valves back in (usually the "worn" ones that were taken out).

The Grose Jet appears to expose more area to fuel pressure, meaning it takes more force from the float to shut them off. If your system is marginal, meaning the fuel pressure is a little bit high, or the float is a little heavy, or the fuel density is a little bit low; then I believe the stock valve may work when the Grose Jet won't.

07-17-2007, 11:20 PM
I'm going to hijack this thread w/ a new inquiry... I'm in the midst of rebuilding my leaky rear carb, and I'm submitting a picture from Nelson's PDF on carb rebuilding:


What is the device he's using to measure the float offset; would NAPA have something like that? I thought I had a small ruler that came w/ Rochester carb rebuild kits, back when I was doing my '55 BelAir, but of course, I can't find it. Any other device recommended? Thanks!

07-17-2007, 11:57 PM
Looks like it might be ditial calipers. Try Harbor Freight.

07-18-2007, 12:02 AM
Don't know about the above question, but will pipe in about the Grose Jets, I have had MGs, Triumphs and AHS, all with SUor Stromberg carbs, when I ran them as daily drivers back in the day I would get the annoying fuel overflow problem intermittently, mess with the carb, sometimes would go away sometimes would take a couple or three dismantling and cleanings.

This was very annoying, starting with my TR4a with strombergs and the two cars I have had since I have put Grose Jets on and since intalled have never had a single fuel overflow problem caused by the needle or balls in my case not seating OK.

Don't know about the new needles, haven't tried them, but the old ones were worse than Grose Jets and for nearly 20 years of driving on 3 different cars I have had no problem with the GJs.

07-19-2007, 08:57 PM
Definitely calipers of some sort, but can't tell if they are vernier, dial or digital.

I tried calipers from Horrible Freight once; were so bad I took them back the next day. Maybe the next pair would be OK and I just got the last ones made on a Friday, but HF's quality control has always been spotty at best, so I won't try again. The cheap dial calipers from Enco work fine for me, and are cheaper to boot.
Still "cheap Chinese", but adequate, IMO.

I used to use vernier calipers, but my eyes have gotten too weak to read them without glasses.

PS, don't get me wrong, I buy lots of stuff at HF. Just not precision measuring instruments.

07-19-2007, 09:58 PM
A simple small sliding T-Ruler from Craftsman should work fine. You can measure the float level (full bowl) as well as float drop (empty bowl) close enough to make it run just fine.