Buy flow tested carburetor jets?

DRG-ler

DRG-ler

Senior Member
A long time ago I found a shop on the Internet that offered rebuild kits with flow-tested jets for Zenith carburetors. Unfortunately, I can't remember where that was... At first I thought it was Renners, but I can't find anything of the sort. Does anyone know where I can get these checked nozzles?

Greetings Andy
 
So my memory has not deceived me. Thanks for the feedback.

I once wrote an email. Calling is not my thing, my English is too bad for that. I only write about Translator here. I'm curious what they answer, whether they have another set of jets.
 
Why do carburetor jets need to be flow tested? If they're the proper size orifice I would think that's all that's needed? Or is there more to it than that?
 
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katy said:
Why do carburetor jets need to be flow tested? If they're the proper size orifice I would think that's all that's needed? Or is there more to it than that?
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Confirming the proper size orifice is what flow testing is all about. There have been many low-quality reproduction jets made and sold in the past that had the wrong size orifice which made the mixture wrong (usually too rich, but not always).

Plus there have been many shadetree mechanics out there over the years that cleaned out jets with pieces of wire and stuff that enlarged the jet's orifice opening and changed their flow.

So if you want to have the fuel flow through the jets and into the carburetor to be correct (as Ford intended) it is good to verify that the jets you plan to use are sized correctly. Once you have them flow tested, you are good (unless you ruin them by cleaning them out with a piece of wire -- don't do that).
 
Tachchen.


Drilled or unstamped nozzles were originally installed. Consumption was 20 - 22 l/100 km.


Only with the calibrated nozzles did I have a basis for adjusting the other subtleties.



Average consumption now is 17 l/100 km. (5% surcharge due to speedometer advance.)


A little bit leaner would be possible, but then the cylinder head temperature rises very steeply on long climbs.
 
I bought "off the shelf" jets from Brattons a couple of years ago, I checked the sizes before I installed them and they were bang on.
The literature I have says: Idle jet: .021", Comp jet: .037", Main jet: .037", Cap jet: .039".
 
I have now received an answer from Rennert. They still have nozzle sets in stock. However, they are reluctant to ship abroad because too many shipments have been lost. But it's not a problem either, since I use myus.com, a shipping service. 18-22L/100km may still be tolerable in the USA, even if the many tank stops are annoying.

Here in Berlin, the price of gasoline is currently the equivalent of $8.29/gal... You'd want to save gas where you can. And the comparison to my uncle's Ford showed it. The engine runs much more economically there, and that was only due to the carburetor. My Ford also ran more economically with its carburetor. So it's time to overhaul the carburetor.
 
Werner said:
Tachchen.


Drilled or unstamped nozzles were originally installed. Consumption was 20 - 22 l/100 km.


Only with the calibrated nozzles did I have a basis for adjusting the other subtleties.



Average consumption now is 17 l/100 km. (5% surcharge due to speedometer advance.)


A little bit leaner would be possible, but then the cylinder head temperature rises very steeply on long climbs.
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Werner, In one of the clubs I belong to, Model As are considered very economical. When I had a standard motor with Zenith Carburettor, I reliably achieved 10-11 l/100km at a steady 70 kph. Given that these cars are about as stream lined as a brick, consumption rises quickly as speed increases.
It is interesting to note that when I installed an overdrive, the consumption did not change but the motor was happier.
Taking a side track now, I have just posted elsewhere how happy I am with my new Burtz engine. The power from it depends on which head, camshaft and carburettor are chosen. On mine, I used a 6:1 head, webber carb and a local grind that goes on a B camshaft. It is a moderate profile (lift is 0.308"). At 85 kph by the GPS, that returns 10.5 l/100kms.
I think you should be getting better economy than what you have quoted.
 
So, after a year and further problems, I finally rode a relatively long tour today. 213 kilometers... (Otherwise only short stretches of less than 80km.) The car runs great, absolutely without any problems and the consumption was an incredible 13.4L/100km.
Rennert's nozzles are absolutely worth their money!

Thank you again for the tip!
 
For maximum fuel economy, you should check the fuel level in the carburetor bowl with a tube connected (instead of the plug) under the main jet. The minimum space between the fuel and the machined gasket surface should be 16 mm (5/8"). It is acceptable to increase this distance (lower the fuel level) to 17.5 mm (11/16").

You adjust the fuel level by adding or removing thin gasket washers from the base of the float valve. IF you are going to err, make the fuel level a bit lower. I have run as low as 19 mm, tend to shoot for closer to 17.5-18 mm.

If you can start and run a cold engine with the GAV closed, the carb is too rich. I must open mine at least 1/2 turn open when cold and then close down later to 1/4 turn open, after about 5 minutes of driving.

On long, steady flat drives, I have seen 11 L/100km (21 MPG).
 
I just ordered a few sets this week and they should be here this week. It's under some drop down boxes on their website. They shipped them right away.
 
I have a B carb, and intake. What size jets? I am thinking the main jet must be too small. I took the gross-jet out, and set the float on the car "wet" with that little clear plastic tube. The engine gets to a point where it noses-over, and just feels like it it running on air instead of fuel. I guess I am thinking the main jet is too small. Opening up the GAV really doesn't cure it. The GAV works because when the engine is cold it sure makes a difference when you open it a bit.
 
Gene F said:
I have a B carb, and intake. What size jets? I am thinking the main jet must be too small. I took the gross-jet out, and set the float on the car "wet" with that little clear plastic tube. The engine gets to a point where it noses-over, and just feels like it it running on air instead of fuel. I guess I am thinking the main jet is too small. Opening up the GAV really doesn't cure it. The GAV works because when the engine is cold it sure makes a difference when you open it a bit.
Click to expand...


Check for a bit of rust or something clogging a passage in your carb, or clogging a jet.

On a B carb, there is that extra little fuel feed built into the throttle shaft. As the throttle opens a lot, more fuel flows through it. Get some carb spray, followed by low pressure air, and make sure that passage is fully open.

After that, you would need to flow test the jets and adjust as needed. If you are at all handy, you can make a jet testing rig and measure them yourself. Target flow rate numbers are available for the B carb on the web.

IMHO, it's not so much about the jet diameter size that you measure that's important, it's about the liquid flow rate that you measure through the jet under controlled conditions.
 
Had it apart (dipped it). Gas flows nice and fast out the line at the carb too. I am inclined not to build a rig, but just buy a size larger from Brattons.
 
I ordered two sets of calibrated jets from David Renner yesterday, also using MyUs.com for shipment to germany.


Together with the order confirmation i received very detailed information about the carburettor, the jets and air filters. i am not going to copy it into this thread as it is 'his' text but i will ask him if he is prepared to send it to us here... ...for dissection and controversy... ;-)
 
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