Two sizes of Zenith Banjo Bolts

[Steve Douglas]

I was having trouble with one Zenith Carb leaking at the fuel inlet, tried new gaskets and checked the mating surfaces, still a slight fuel leak. I decided to look more carefully. I pulled out my small collection of banjo bolts and started to compare them. The one bolt that was leaking had a V stamped into the head, the side that didn't leak was plain, no markings. Measuring the bolts I found a small difference. The ones with a "V" were 29.27mm long and the shoulder was 11.97mm diameter. The unmarked ones were 28.10mm long and the shoulder is 12.00mm diameter. The longer bolts will bottom out in the fuel inlet of some of the carbs, and while they seem tight they aren't compressing the fiber washer enough. The longer "V" bolts are more than one tread longer. Also the inside diameter and the holes are slightly larger. The new red fiber gaskets are 11.99mm id. and fit the V bolts but not the shorter bolts. I had some older fiber gaskets and they were 12.02mm id.
After fitting the shorter bolts to both carbs and the old fiber washers, no leaks.
Anybody else found this problem?

[Martin Benade]

Not sure of all that, but I think the V is for vergassar, probably spelled wrong. That is so you won't try to use it in the fuel pump that has a slightly different thread.

[Ron LaDow]

Not sure of all that, but I think the V is for vergassar, probably spelled wrong. That is so you won't try to use it in the fuel pump that has a slightly different thread.

Correct. Except for those who have swapped them ('darn thing is awful tight!') and find they have leaks.

[Martin Benade]

I have probably done that, but fortunately I can't remember.

[Steve Douglas]

The A/B fuel pump banjo bolts are very different than the Zenith inlet bolts. Bigger threads, and holes. The ones I was showing will both work in some Zeniths, but not all, as the thread depths are slightly different
The left one is the fuel pump and right Zenith Carb inlet.

[Vic Skirmants]

Steve; maybe the unmarked one is for Solex? I'll have to look at my stash.

[Ron LaDow]

The A/B fuel pump banjo bolts are very different than the Zenith inlet bolts. Bigger threads, and holes. The ones I was showing will both work in some Zeniths, but not all, as the thread depths are slightly different
The left one is the fuel pump and right Zenith Carb inlet.

Interesting. In all the carbs (and bolts) that went through here, I never ran into a length difference.

[Steve Douglas]

The unmarked bolts I think are the originals to my 59 coupe normal, and the PO3 carbs dated 8/58. Not sure where the longer ones came from, but have 6 long and 4 short, and being I have 2 complete running engines from the 58/59 era, guessing the short ones are originals and the 6 long are from another vintage, maybe the "Cs" ? The longer ones will work in a few of my extra carb tops and the rest it bottoms out. Also the current red fiber washers are very hard to install onto the shorter bolts, they will fit with some manipulation, they slip on easily on the long bolts.

[John Brooks]

Maybe it's the photo but one looks like it's is 1.0 and the other is 1.25 pitch. Webber and solex use the same size bolt except for the thread pitch, they start but then you are screwed when they get close to tight. Go measure the thread pitch.

[John Hearn]

Yes the V stands for Vergaser, German for carburator........
KTF
John

[Bruce Smith]

Here are the two correct style banjo bolts used in a 356/912 motor, both M12 X 23mm. The bottom are are the finer thread pitch (1.25mm) used with Zenith and Solex carburetor fuel ports. The top are a coarser thread pitch (1.5mm), correct for use with DVG fuel pumps. If you try to use one for the other, you will get some resistance. If someone has forced one pitch into another, its time for a Helicoil.

[Dick Weiss]

Banjo bolts:

Both Solex and Zenith carb tops use the 12 x 1,25 which have the V stamped on the head. The non-stamped head is 12 x 1,50 which is used on the early "rocker arm" fuel pump. If the wrong bolt is used on either port, distortion will damage the threads causing a leak and over-tightening will strip them out. I don't use Heli-coils, but make a bronze insert bonded w/JB Weld and reface the boss squarely for the seal.

I have several Zenith top covers for $125 exchange--mailed or swap meets; Rarely, Solex tops don't get damaged enough due to their cast aluminum material vs. Zenith's soft pot metal material.

[Vic Skirmants]

I don't think the Solex ones were ever stamped with the V. Or were the 1960-61 Solex ones stamped? I know the later ones weren't, because they no longer used the early fuel pump.

[Brad Ripley]

For what it's worth .... In the Stoddard inventory, here are the dimensions of the banjo bolts, carb and pump:
Carb bolt, Solex and Zenith: 616-100-867-00 12 x 1.25 x 22.45 Diameter of shoulder is 12.00 See photo below.
Carb fiber washer: 616-108-423-00 ID is 12.12
Note: length measure for all metric bolts is under the head to end of threads.

Pump bolt: 900-175-020-01 is DIN 7643 12 x 1.50 x 24.00 no shoulder see photo below
Washer is same as for the carb bolt.

BTW, the pump bolt, 900-175-020-01, is used for earlier 32 & 40 carbs and early fuel pump.

[Steve Douglas]

Brad, you are correct as usual on the original sizes of bolts for the Zenith and Fuel pumps and the red fiber washers.
However, I found that some of the currently offered red fiber washers are smaller in id. 11.98 and 15.94 od. compared to the older ones of 12.02 id. and 17.0 od.. These came from Intex and CIP and are unbranded kits sold at cheap prices, $22/23, and these washers are very hard to get into the 12.mm shoulders, but fit nicely on the longer "V"bolts.
I was at a friends house who has had only late C cars forever and looking through his stash of parts I found some of the longer "V" bolts, as well as a couple of the shorter ones. I have tried 13 different tops of unknown vintages and 3 of them were threaded shallow enough for the longer bolts to bottom out before being tight on the banjo.
Maybe the late C cars had different bolts and machining of the tops?