Zenith Stromberg questions

My engine is running too rich. I have rebuilt the carbs from the ground up and I pretty much have a stock setup for the year of my car with the secondaries in play. Engine has a Pertronix ignition 10deg BDC at 700 idle and it looks like I have the chokes in the right way.
My notes say I set the floats at 16mm back when I rebuilt them. Here are some specific questions…
1/ Should I increase it from 16mm? If so to what?
2/ Anyone know how much that will that change the mixture? i.e. is it even worth doing?
3/ Where are the ID stamps found on the mixture needles? I removed the mounting screws to remove them so I could look at the biased base but they are stuck in the pistons and I don’t want to F with them, so I’m assuming they are B1E’s. They look like they are in good shape with the base flush to the piston.
4/ Jets are pressed in @ 0.065" below the bridge. What about changing it?

I know all about Joe C’s adjustable jet kit for the ZS. If I can’t get this leaned out, I might order a pair. But for now just looking for some advice so I can learn more about these carbs.

1/ from memory 16mm sounds right

3/ I believe you are correct, I think the stamp is on the shank up where you cant see it unless you pull them out. are your carbs 3207’s? the number is stamped on the bottom of the manifold mount flange. if they are and you are reasonably sure they are original then the needle should be a B1E. however…

4/ 0.065 seems way to high for the B1E and orig carbs. pretty sure they were originally around 0.100 below the deck.

I went with the curto adj, and in trying to lean things up with B1E needles anything above 0.085 was way too lean.

you should be able to push the fixed jets either direction, they are just press fit into the carb body.
I used a couple deep sockets and a big C Clamp to move, and then ultimately remove them. others have had luck using a punch and light hammer taps to push them down or out.

I did a quick check on a needle, its actually on the shank INSIDE the collar that is held in the piston. this needle is spring loaded, you can pull it down even while clamped in the piston, the number is stamped around the shank, in this case its a B1A

also here is a chart from the Stromberg book

Bob F

Bob, where did you get those great looking vice pads ?

In my opinion the adjustable jets are the way to go here - so easy to make small precise adjustments (even along the side of the road) until you get the mixture exactly where you want it.

I used a set of jet carriers from TR4 carbs (just because I like doing things the hard way I guess) but Joe’s kit makes it dead easy.

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Bob, great info and helpful photos, especially on the metering needles, thanks.
Interesting, if you think that 0.085" should be way too lean, and I’m at 0.065" I should also be running lean and not rich. Do I have that right? Which makes me wonder what’s really going on.
Let’s see if anyone else has any ideas.

Geo, I may end up with Joe’s kits yet. And to answer Bob’s question, I’ll have to double check and look again for the carb number when I’m close to the car. My memory is not that good!


They came from Brownells.com. a giant firearms parts and tools supplier.
search for Magnetic Soft Jaws, or 100-002-397WB.

They fit my big Wilton Vise perfectly and are a nice set of poly clamps that have magnets in them


If you decide to go with Joe’s adjustable jet setup (really nice by the way), I’d have him send the needles he recommends for these as well. May as well take care of any possible issues all at once, imo.

Anthony I struggled with running rich too. I damaged one needle trying to get it free of the piston. Rather than go with the adjustable jet I called Joe Curto and asked for adjustable piston/needle assys like came on the later ZS carbs like on the Series 3. This way I could just swap over the diaphragms and drop them into my carbs and easily put it back original if I did not like them. It was $137 total for both carbs in 2015. Runs much better after I leaned them out some.

68 E-type FHC

David, I didn’t know that the S3 ZS carbs had adjustable needles. You’re saying they can drop into my current carb body? That’s interesting. If that’s the case, makes me wonder why some buy adjustable jet kits and go to the trouble of pressing them out and replacing them.

Just my two cents on this. First, pressing out the fixed jets is pretty simple. I made it more complicated by using a C clamp and sockets. Installing the new ADJ jets just requires screwing them in from the bottom, there is no pressing or fumbling.

The thing I really like about the Joe setup is that I can adjust things with the motor running and not having to remove anything.

I carry an extra socket that I wrapped with tape and made 1/8th turn gradients on it.
SO I can drive, stop n fiddle, drive a little more, repeat until I like how things are running.

That being said, I will admit that after dialing it all in a few years ago I haven touched anything since, so maybe there isnt enough to justify one over the other. And I get the fact they arent cheap. but there sure are nicely made. I suppose if I had bent or worn needles I might have looked at the other option.


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Ideally that’s how carbs are suppose to work. Years ago someone on this forum once said carburetor is a French word meaning “Don’t touch me”. meaning, of course, once they are dialed in, leave them alone.

Thanks Bob, good photo thanks for sharing. No question, Joe’s kit is well built…

I originally stated…

Bob, If you found that anything above 0.085" to be lean on your carbs, would it stand to reason that mine at 0.065" should be running more lean than yours? Yet I’m running rich. If that is true, I must have something going on that I’m missing or overlooked. Like in the chokes maybe?

FWIW - after many iterations of small moves I seem ideal at .078 (2½ turns of the adjustment):

Do assure the choke (enrichment) is fully off… but I think engine condition, float level and other factors are at work that make it difficult to compare settings car-to-car.

Geo, Now I’m starting to second guess the work I did on the chokes. I’ll double check them when I’m back at the car. With all of the tasks I’ve done twice on this car to get it right, I swear I feel like I’ve put together 1-1/2 restorations. :grinning:

About float levels, I’m at 16mm. But from the archives, which is usually my “go to” starting point, some say that it really doesn’t make much of a difference. Others rely on a setting of 20mm and say it’s best to help lean out the carbs.

Anthony, yes later ZS carbs had adjustable needles that can be adjusted using a long allen wrench that reaches down to the bottom of the damper oil reservoir into the adjuster to raise or lower the needle. I do not know when Jaguar switched over to them from the fixed needles but a guy with a Series 3 showed them to me on his car. Here is what the tool often looks like but I made mine


68 E-type FHC


For me as I raised them the car wouldnt run above different RPMs. above 0.08 I couldnt rev past about 3500 with serious problems. But as Geo states, there are so many variables that I wouldnt say that setting wont work in your car. maybe it is the chokes and some mechanic had tried to lean things by raising the jets. But this brings it back to the adjustable jets.

Joes instructions say to start 3 turns down, that puts them in the 0.09 to 0.1 range. Geo’s car is happy 1/2 turn leaner, I think I am somewhere in between Geo and the “3 turns” myself.
I think I calculated that each “flat” of the adjusting nut is about a 0.006 change. and each full turn is about a 0.035 change. thats from memory, could be off a little.


I also converted my Stroms to the Curto adjustable jets. I do not have the ability to fine tune by sound or feel as some of you can. Installed Innovate system that runs off two O2 sensors in exhaust down pipes, this way can adjust by the numbers that are displayed on gauge. Have found that the Stroms are not very accurate, one jet may be higher or lower than the other and give similar A/F ratios. When first installed my fear was running too lean and that caused O2 sensors to fail, no longer a concern. Just watch the #s while driven hard.

Close - as I recall the threads on the adjusters are 32 TPI (same as an SU I think).

I am envious, I think thats even better. and as I seem to recall , after dialing mine in they did end up at slightly different depths. Which at first had me concerned, but I left them alone and now I am glad I did.