Zenith Carb Question(s)

[Dick Weiss]

Two different things about Zenith carbs;

1. The choke cover screws aren't flat headed--they're slightly crowned.
2. I've had several Zenith choke cover screws w/o star washers and they were lightly "staked"
(w/a screwdriver tip) next to a screw-slot/edge to lock it in position. It still can be R & Rd if needed.

[Ken Tuvman]

The solution is pretty simple, and I've done a lot of them (hundreds). I usually use Walker kit pumps and have only had a couple that were difficult to seal. First make sure the pump cylinder in the carb housing is clean and smooth. If it's pitted, which is rare, you're going to have problems and probably will need a new body. If needed, run a brass small brush or a some Scotch-brite inside the cylinder but don't overdo it. Clean it and dry it good (no oil, WD-40, etc.) Then expand the skirt of the dry leather sheath of the new pump just a little bit, again don't overdo it. When you insert the pump, guide it squarely into the cylinder to ensure that it goes in evenly all around since you've expanded it's skirt. Insert it dry, i.e. no oil, gas, or solvent. Then do the set-up up on a bench with mineral spirits to adjust float level and pump volume. Wait a few minutes after you've filled the bowl so that the pump sheath is sufficiently wetted. Then manually work the pump through its full stroke with the pump rod disconnected until it begins to squirt from both injectors. Problems can arise if you haven't cleared and gauged the pump jets and injectors, ensured their seats are clean and smooth, and installed new pump jet o-ring seals. Once they're squirting, connect the pump rod to measure volume. A good starting length is 70mm. Longer is less volume shorter is more. I use a syringe to fill the bowls - I wrote a Registry article a while back on the set-up.

Regarding "Expanding the skirt just a little bit - what is the proper "technique" to do this?

[Brian R Adams]

Thank You Bruce - would love to see a link to your story and read it.

A simple search for "syringe" brought me to Bruce's post. Substitute a large plastic syringe for my outboard motor priming bulb and filter as a pickup dongle:

viewtopic.php?f=1&t=35783&p=278240&hili ... ge#p278240
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[Brian R Adams]

In the article Ron LaDow published on refreshing Zeniths he wrote:

"Fit the idle mixture screws (with springs) by hand. Gently; no fresh grooves on your new mixture screws. After you try it two or three times, your fingers will tell you when they stop. If you ‘groove' one, you have spares. Back each of them out 1-1/2 turns from the ‘stop'."

I wanted to avoid bottoming out the mixture screws with the springs in place, as it's too hard to feel them bottom out without going a little too far (the compressed springs make you use force to advance them that last bit.) Without the springs, the screws rattle around in the holes, and allow you to be very sensitive to bottoming out. So ... With springs set aside, I took a new mixture screw and noted the position of the screwdriver slot when I barely engaged the threads in the hole. From there I turned it clockwise 1/2 turn at a time by watching the slot. Counting 1/2 turns, it took 14 (or 7 full turns) plus about ~1/8 turn to bottom out gently. This turn count seems consistent (as expected) across all 4 idle mixture screws/holes.

Now I can put the springs on, get the mixture screw threads just engaged, then add 11 half turns (or 5.5 full turns) without ever bottoming out the screws, and know I am ~1-1/2 turns from "closed". Later, when tuning the idle mixtures, I add or subtract 1/4 turns from the starting position, and, by keeping track, avoid coming near bottoming out, and if I do approach bottomed, I know there's an abnormal rich condition in play that needs to be addressed elsewhere (idle jet, float level, ...) In this way, there's a high likelihood of installing and adjusting the new mixture screws without ever bottoming them out and scoring the conical tips.
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[Brian R Adams]

...

Posting here, as this is the active Zenith thread:

Ron, in 2014 you wrote:

The kits typically include .04" and .05" alum shims and .028" fiber shims. And if you are rebuilding your carbs, hang on to all the shims that you find. Finally, these guys ( http://www.pinzgauer.com/parts.php?cat=pinzgauer&id=3 ) have .02" shims.
Since they all need at least two shims, some mix of this and thats will always get you in spec.

In playing with the loose washers in the kit, and the provided float valves, I notice something bothersome. On the new valve (as on the old) there is a shoulder which centers the included fiber washer perfectly. However, the shoulder is only "tall" enough to center the bottom washer. If I stack another washer on top of it, the second washer is above the shoulder and can float laterally. I see this as a possible issue in preventing any leakage of fuel past the washer stack. The ideal scenario is a single aluminum or copper washer with the proper ID/OD that is the desired thickness.

How do you address keeping the washer stack concentric? Is it just a matter of holding them ~concentric while tightening the valve into the carb top? It occurs to me one could apply a scant film of sealant between the washers and clamp them together, concentric, to dry before final assembly.

PS My Walker kit holds aluminum washers .040" and .060" (not .050") plus the red fiber .028" packaged with the float valve.

PPS Here's the link to the .020" (0,5mm) Ron referenced:

https://swissarmyvehicles.com/pinzgauer ... enith-ndix

They also sell a .040" (1mm) washer:

https://swissarmyvehicles.com/pinzgauer ... enith-ndix

Note: The .040" (1mm) aluminum washer in the Walker kit will work as a shim, but it is intended for the accel. pump pressure valve, and it has a slightly larger ID than it should, so it's a looser fit around the shoulder on the float valve. I happen to have some of the .020" (0,5mm) and 0.040" (1mm) aluminum washers from SWA (see above) and these have smaller IDs for a better fit on the float valve.

Brian

[Ken Tuvman]

Good Morning - want to try to set the floats using suggestions above - don't have a banjo bolt handy to make a pump like Brian did on post #25

Found these (2) on Ebay - would either of these work?

Thank You

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[Brian R Adams]

Ken,

I believe they will all work, but I would prefer red fiber washers myself, as (ironically) they don't tend to wear out (work harden, scuff) with repeated cycling. The one example has a 1/8-27 pipe threaded hole in the head for attaching a pressure gauge. I'd rather put the gauge inline (w/ 'T') so I wouldn't have to plug that hole if I omit the gauge. I also don't like the idea of the gauge hanging on the bolt anyway.

Brian

[Brian R Adams]

My '59 is lacking an insulation pad behind the engine on the firewall. While removing the Zeniths from my friend Mel's '65, I discovered the 12mm wrench I have been using was too long to manipulate the carb hold-down nuts behind the left (port) side carb. The insulation in his car interfered. I had a stubby Crescent wrench that worked, but fussily. (Those damn things never stay adjusted in use, especially fumbling around blindly behind the carb.)

I endeavored to purchase an inexpensive stubby 12mm wrench, not much longer than 4 inches. On Grainger's web site I found this little gem. It's 4-3/32" long, very slim, well-finished, and the box end has thin walls. Honestly it looks a lot like a Snap-On, but the price was only $2.91 plus local sales tax, and since I am lucky enough to have a Grainger brick+mortar store in my city, I had it shipped here "will call" for free! I figured for that price it had to be made in China, but no, it's made in Taiwan, which is about as good as it gets nowadays in my book.

Here's the link to the little bugger at Grainger (the photo there is not of the actual item):

https://www.grainger.com/product/produc ... 12mm-5MW24

Here's my wrench:

wrench.jpg (2.05 MiB) Viewed 802 times

Brian

[Heidi Frances]

Hi Ken,

A couple of things I did on my carbs... I filled those little silver caps from the inside to keep the body from weeping. That was driving me nuts trying to find the leak and it was those little caps all along. Next was an issue of the car slowing when hot at idle (like at a light after a bit of a drive). I finally figured it out. The left carb float level was just a tad too high. It tested to spec when cool, but sitting on the left side it gets a bit hotter there. I just put another small shim on the needle and seat just on the left side and it is rock solid on a hot idle.

Good luck on your rebuild!

Franny

[Ken Tuvman]

Hi Franny - feel like we’re friends - love your You Tube videos

I think You meant to say filed not filled & you’re referring to filing tabs on carb top tang so the top fits nice & snug on main carb body.

Learning so much from the 356 community & making new friends too.

Still a ton to do but eating my elephant one bite at a time.

Building a good support network.

[Heidi Frances]

Hi Ken,

Take a look at your carbs on the side with the big round choke cover... Towards the bottom, you'll see two small silver caps that are meant to seal small holes. On our car, they were just ever so loose and fuel would weep through. Last time I had the carbs out I used a burr tool and roughed up the hole from the inside and filled them with JB-Weld. With them sealed; no more weeping. If you aren't comfortable with JB Weld, there are other products. Also, if gas is getting out, air is also getting in. Properly rebuilt and dialed in these carbs will make the car run beautifully so if you are noticing issues you know are the carb, just keep at it Glad the videos are helpful We just drove the car up to Boulder and back (about 50 Mi total and it never skipped a beat. 356s are just the best!

Franny

[Dick Weiss]

Ken,

Did you receive the carb parts I sent last week?

Dick

[Ken Tuvman]

Good Morning Dick - received the parts in Saturdays mail - thank you very much! It seems every step I take with this project uncovers more neglect of previous owner(s).

Dick sent me a spare banjo with fuel hose so I can bench set my floats & accelerator pump(s) - I'd purchased my rebuild kits from 356 registry and they Kindly sold me a new carb top for a nominal fee because a previous owner had drilled out the portion of carb top where A/P resides with a funny looking bolt and screw (look at earlier posts on this thread). That top is fine but the existing one that looks "good" has a stripped female thread where the banjo bolt screws into carrying fuel.

Discussed with my younger son, who works at a professional auto shop and he plans to show me how to repair this afternoon with a Line-Seat kit today - it's supposed to be stronger and more long-lasting than Heli-Coil.

This project reminds me so much of my BMW R6LS project that needed EVERYTHING. A therapeutic project but sure a lot of speed-bumps to get to the pot of honey!

p.s. the great news is the friends I'm making here - thanks also to Al Zim and Dick Weiss for being kind and great and offering so much knowledge and also to Tom Wavrin for Kindly sending me his Charlie White Zenith book and testing kit to help me get my carbs properly adjusted - Tom also provided me with a beautiful Leistritz exhaust to replace my mouse house that was trashed - no shortage of great resources here! I've had similar experiences on the BMW m/c forums and my mechanical skill have improved so much by meeting folks like you! Thanks!!!

[Ken Tuvman]

My son showed me how to fix the stripped thread in my Zenith
Carb top with a Time-Sert kit - pretty impressive - he used red
Loctite and a special tap type tool to insert the thread.

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[Ken Tuvman]

Next step - bench setting the floats & accelerator pump