Zenith 32 NDIX Jet Cover Gasket Quality Control

[Pascal Giai]

I don't know you guys, but I am replacing regularly the same jet cover gaskets on my Zenith 32 NDIXs due to quality issue...
The cover needs 2 gaskets, the O ring for the cover plate #33 and the tinny fiber/aluminum seal for the bolt #35 on the diagram bellow.
I know Carburetor Rescue uses the aluminum gasket for the bolt, but these gaskets do not like to be re-used and need to be replaced each time, the fiber ones can be re-used and last much longer.
Sometimes I even use 2 gaskets stacked on each bolt...I find them at my hardware store for very little money...
The O rings are more difficult to locate and I am not sure if I am doing the right thing in ordering them from Stoddard ??? ( part # 616-100-838-00 $12.89 each )
The material doesn't survive too long with modern gas and the leaks are occurring too often to my taste. Sometimes they last only 6 months...
Does anybody know a better source for these O rings ???

Thank you for your expertise !

Pascal Giai, San Diego

[Ron LaDow]

2nd image: Someone has already ground off some material in the hopes of getting a better seal. It will not work and others here hope adding but one more gasket will do the trick. It will not.
The leakage has to do with the misalignment of surfaces, see here:

La Dow Zeniths 2-17.pdf

(339.98 KiB) Downloaded 158 times

Make sure the surfaces are normal and be done with it.

[John Hearn]

Pascal how often is often?
You are using the correct rubber gasket. I see from the package it was made in 2012 and a usable date (Verwendbar) till 8th September 2022.
Do you have a photograph of one that leaks?
As Ron has said leaks usually occur because of bad surfaces and alignment. These often caused by overtightening......
If it is the actual "rubber" breaking down due to modern fuels you should go back to Stoddard who should take it up with Porsche.
I beleive Porsche has a three waranty on parts like this.
KTF
John

[James Watters]

I seem to recall that someone was making the rubber gaskets out of a different material that would not break down. This was 4 or 5 years ago. Was the material Viton?

[David Jones]

Viton is resistant to gasoline. I bought mine from a bearing supply store. If you pay more than $0.50 cents for one you must be getting the de luxe version. I don't remember the size but measure one and buy it from Amazon if you are feeling lazy.

[Don Gale]

ditto, that cover has seen better days. new covers are available at partsklassic for $16. Viton is a better choice vs. buna-n, but be aware viton is usually 90 duro and will require more force to compress and seal. buna-n is most likely going to be 70 duro and will compress easier.

[Dick Weiss]

The O-ring for the Zenith jet cover has a special thickness which is compressed when the bolt is snugged up and NOT tightened to bottom-out metal-to-metal--especially the early Zenith bodies not having the extra gusset under the bolt-boss which will be pulled outward when over-tightened preventing the seal to be squeezed properly. The casting's boss can be squeezed back flush to the surrounding edge of the opening.
I've never had a problem w/the correct O-ring and the photo shows that the O-ring needs to be roll-twisted to be retained in the cover's slot--no glue is needed. If removed later, the seal will stay rectangular and if it's still soft, it can be re-used.
If the jet cover has been over-tightened giving a slight cup-shape, it can be compressed in a vice using a 3/8"
diameter plug About 1/2-5/8" long on the inside of the bolt hole and squeezed.

[Pascal Giai]

I replaced the aluminum gasket with a fiber gasket ( $0.76 at my local hardware store ) and the O-ring with a Porsche part 616-00-838-00 ( $12.89 ) good enough to drive to the "Bella Collina Concours" in San Clemente on Sunday.
So far no leak, but for how long ?
Today I went to my hardware store ( Marshall's 8423 Production Ave, San Diego, CA ) and bought O-rings M432.
They fit the jet cover perfectly and seat well on the carburetor body...I am currently testing one as a sample in gas...
They cost $0.68 and are a little thicker ( 3.8mm ) than the Porsche part ( 3.4mm ).

Pascal

[Ron LaDow]

The fiber washer means the leak is a bit slower.

[Bruce Smith]

Pascal -

I'm curious about the fiber washers you found at the hardware store. These aren't such a standard size, with an OD of 10 mm and an ID of 7 mm. Is this the size you found? If you use a larger OD and try to make it work, you will need to over tighten the bold to cram it in and it will leak.

Cheers,

[Pascal Giai]

Pascal -

I'm curious about the fiber washers you found at the hardware store. These aren't such a standard size, with an OD of 10 mm and an ID of 7 mm. Is this the size you found? If you use a larger OD and try to make it work, you will need to over tighten the bold to cram it in and it will leak.

Cheers,

Fiber washers I bought are 3/8 x 9/32 x 1/32

[Mike Wilson]

There are also steel washers with a rubber insert. Has anyone tried those?

Mike

[Paul Hatfield]

I used to have a problem with the covers leaking until I really dove into cleaning and inspecting the cover very carefully. Because of over-tightening, mine had a crack in the cover at the bolt hole opening. This is soft metal, and it is easy to over-tighten and damage them. Also, without careful inspection, it is easy to miss the flaw. As a side note, when you clean these notice the foundry casting on the inside. I discussed this with Brad Ripley and found that the ROKA casting stamp stands for RObert KAhrmann Lobberich company, Germany, more known for precision castings for the model train hobby.
Anyway, as Ron and Dick pointed out, the surfaces must be in good shape, or you can mess with this for a long time.

Hope this helps-

[Steve Douglas]

I have three different O-Rings for Zeniths NDIX 32 side covers. #1 is from a recently purchased Royze, measures .35mm diameter and Id 32.52mm, #2 is "white label" but possibly rebadged EMPI gasket only kit, bought from one of the better vendors, and it leaked, it is .320mm diameter and Id of 32.7mm, and #3 was from a VW swap meet, unbranded and it is .33.6mm diameter and has smaller Id .31.05mm. I have been using the smaller ones with good luck, basic kit $9.50 but some gaskets are untreated paper and wick gas, making a smelly and damp outside of the carb. The Royze also work well, and they range in price from $29-65, but may have some wrong O-Rings fiber instead of aluminum.

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[Pascal Giai]

One more time the " Porsche " O-ring did not survive California Premium...