Zenith Rebuild - My First Carby Project

[lrodri64]

Hi Rodo!
From who you bought the venturies?

Thanks for this thread.
I'm working on mines also.

[Demetri]

Great thread! Thank you!

[rodoredas]

It's obvious but I made sure the pre atomisers are orientated the correct way round with the fuel inlet opposite the emulsion tube and clip recess on the clip side, and the clip also right way round with the bulge face to the atomiser. I installed these together, not the atomiser and then the clip, but by inserting the clip half way and using the atomiser to hold it in place while pushing gently on the atomiser and pushing the clip at the same time.


The new pump diaphragm and spring went on next with the cover and 4 retaining screws


I did the Idle jets, idle mixture screw and air bypass screws next. The new idle jets seem slightly longer (although photo does show that) than the old ones and none of the o-rings on the kit would fit. The largest o-ring in the kit is shown on the idle jet below, but it's too small. Enquiries on pelican about the use of the o-ring on the Idle Jets indicated these are not necessary as the jet rests firmly against the inlet. You can see the old o-ring and new Idle jet with no o-ring. I had new Idle mixture screws and springs and these too require an o-ring. The issue I have with the kits is there are no instructions or guidelines to indicate what o-ring goes where. For seasoned experts this does not prevent problems but for DIY's it would help if there was at least some basic guide. Via process of elimination i choose an appropriate sized o-ring for the idle mixture screw and installed it by mounting the screw in a vice, using 2 old mixture screws to get the o-ring in place. I guess a small compass would do the same trick.




Idle mixture o-ring install and bypass screw installed, with grub screw in aux fuel inlet, new springs on idle mixture

[rodoredas]

I had ruined some of the threaded plugs when getting them out as explained earlier and the new ones installed easily. New Main jets and holders installed, I went for 165 mains, purely on recommendation and opinion on pelican




New float level needle valves and the replacement threaded bolts too, reused some the washers and used new ones from the kit where appropriate, again little or no guidelines with the kit, at times frustrating.




My new float had arrived and with fashioned twisted screw driver managed to get the screws securing these tight. To a point I found I could use a small screw driver but the bowl itself prevents proper access.



The top could now on but it too should be checked for proper orientation, left incorrect, right correct


More gasket issues with those supplied in the kit, these that sit between the body and the manifold are just the wrong size, they just don't fit, further adding to my frustration, the kits are not cheap and at this stage of the job I'm wondering what is good about them. Further delays sourcing some locally at extra expense.



cheers

[rodoredas]

These carburettors have been on a Sporto at some time in the past because the manifold has this check valve that is used to source vacuum to the Sporto solenoid and vacuum tank. It was removed and plugged. As was the Solenoid for the auxiliary unit.



The cam disc and shaft rod for the pump jets were installed next and there some alignment to be done here to ensure that the fingers on the shaft rod that activate the pump diaphragm are vertical. The position of the bracket for the retaining spring shown here during teardown is incorrect, they are placed on the outside of the body not the inside as shown , it should be on the bolt/screw that can bee seen top middle according to the manuals.



The fuel line hubs were installed minus the small filter shown here as part 11, general opinion is these are not needed. There was none installed when I took these apart as the these pix taken during teardown show. I did manage to source some but alas they are the wrong size. On recommendation I'm using Goss fuel injector hose.



I have some new fuel filters ready to go and a Syncrhometer for some test later. I'm using insulation gaskets between the manifold and engine, these are 3mm thick with other gaskets either side, sourced from UK.



Just about done, Air Filters arrive...

cheers

[rodoredas]

The new Air Filters arrive a couple of weeks after ordering and we continue, they come complete with all the necessary nuts, bolts and gaskets and fit will. Gasket and base plate are installed along with the old now polished up intake trumpets, filter and top.



The holes in the flat top need drilling out a fraction as the long bolt threads just don't fit.



I get hold of some new gaskets for the manifold to body and mount the carbies to manifold, attach the throttle shafts, newly painted. Not sure I like the silver but it will do for now.

These haven't turned out too bad, stripping and rebuilding the second one took a fraction of the time it took to the first one with less issues.




I then got to play with the angles and setup of the actuating lever and wrote an odd thread about all that, if your game!! its here

This has been a great experience and I've learnt heaps but where to now. I'm hoping to get my 3.0L engine loom in a week or so, (been waiting since October!), I can then complete that engine build, get these installed. The plan is then to remove a seized 2.7L from a project car, a 77 Targa and install the 3.0L with these carbies and a 5 Speed LSD - one day!!



Without this site and all the technical expertise and contributions from others who are experts in the field none of this would be possible.
Thanks

Cheers

[wayner]

Fantastic thread
subscribed!

[1976 TN Porsche]

Nice Carburetor Build! Good looking car too.

[924CarreraGTP]

Just for added information on rebuild kits, Allstate Carburetor obviously sells the same kit as pelican for the 40 TIN Zenith, but for a little over $50. The reason I'm pretty sure it's the same kit is because I bought two from Allstate years ago and recently had a fuel leak between the manifold and carb. So I used the manifold gasket supplied in the kit, and it too was the wrong size from bolt to bolt. However, the intake hole is the correct size, so I gently knicked out a slight bit more of a hole with a paper hole punch toward the outside of the gasket on both sides of the gasket bolt holes, and then the gaskets fit fine and I have had no leaks since. The kit is not a perfect kit by any means, but at least I didn't spend $90+ on it. Not to be down on pelican by any means. Pelican is a great forum, and a good vendor, but like any Porsche parts vendor it's hit and miss for some parts. Pelican is just selling what they can get. At least now I know not to buy a kit from Pelican expecting a better product. So this write up has saved me money. Thanks again!

[rodoredas]

Thanks 924CarreraGTP, had a look at the AllState kits and they look identical and almost half the price, still half the bits I found I didn't use. There has to be alternatives. If I did this again I would try and source from alfa1750, but there must be others who supply.

Cheers

[rodoredas]

For 15 months I've been busy restoring the Targa shown in previous post, today May 2nd 2015, I started the engine to which these Zenith carbies are attached - They Work - !!! see the last post on the link

cheers

[nilknarf]

Originally Posted by rodoredas

For 15 months I've been busy restoring the Targa shown in previous post, today May 2nd 2015, I started the engine to which these Zenith carbies are attached - They Work - !!! see the last post on the link

cheers

Congratulations! That first startup is music to the ears, isn't it? Mine ran horribly for the first little bit, but following the available tuning directions (after using the rebuild kit, of course) will have your car singing sweetly in no time- mine does!

_c

[Luislang]

Congratulations on the startup! Few things are more satisfying than hearing a Porsche come to life again. You should upload a video to YouTube so we can share in your achievement.

[Arts911]

Nice post . I sent you a PM

Arthur

[stephers]

Good job,

I really like the Zeniths once you have gone thru them and set them up properly( which looks like you have with the bigger venturi's and plugging the enrichment circuits


Here is a set that I did for a fellow a few years ago

Thanks, Rick

[rodoredas]

That's nice work too Rick, yeah 34mm venturi. I should have followed your lead and plated some the throttle lever bits, looks much better. I guess I can still do that, the Targa that these are in is not fully going yet, had to send the new ignition unit off to get replaced and it's just come back, so I have a little more to do on that project

cheers

[chris_seven]

These are some 40TIN carbs we just completed.

We have standardised a system to refurbish Zeniths where we hone each throat and increase diameter 0.25mm and fit a new Throttle Plate which we manufacture.

We also line hone the throttle shaft bores to 0.25mm oversize.

We have throttle shafts in both standard diameters and 0.25mm oversize, which are currently out of stock but we will have more in the near future.

We have modified the shafts with a cut away section to both improve air flow and to allow us to use the same throttle shaft screws on all of the other shafts we will be making. (Weber, Solex and MFI)

We have reduced the end section to 5mm diameter so we can also share the shaft coupler with the Weber carb and improve pricing for new couplers. We could make shafts without the reduction in section but I am not sure there is enough demand.



I would agree with comments about gasket quality in many of the repair kits - they don't fit well and the materials never look very good.

We have made our own gaskets using Klinger materials and they are a decent fit.



We are slowly working our way through a range of parts.

We have re-manufactured all of the springs for the Zenith, Weber and Solex 40Pl and will make the MFI springs in the near future.

We have Diaphragms in a Contiflex material that is Ethanol resistant.

We have gaskets for Zenith, Weber and Solex 40Pl all in Klinger materials.

We have insulators in an Epoxy Fibreglass Flame Retardant material.

We have the O Ring seals for all three carbs being made in Viton B and all of the fibre and copper sealing washers to the correct thickness but these aren't finished yet.

We have manufactured Zenith Venturies in 34 and 36mm diameter and will have 32mm in the near future, Weber venturies in 34 and 36mm and Solex 40PI in 32, 33 and 34mm.



We have just completed all of the hex nuts, studs and cheese head screws used on all of these carbs as many are missing or in poor condition and are not commonly available.

There are a variety of reduced hexagon M8 full and half nuts with either single or double chamfers most are 12mm AF but one is an 11mm AF and we have a full selection.

The cheese head screws used on the Solex and Zenith are an older style than the parts now being sold so we have re-manufactured these screws to the original pattern .

We have also made the M5 studs for the carb bodies and M8 Studs for inlet manifolds.

We have a few more parts to complete, such as drop links and then we will be able to supply most parts.

[porschetub]

Originally Posted by rodoredas

For 15 months I've been busy restoring the Targa shown in previous post, today May 2nd 2015, I started the engine to which these Zenith carbies are attached - They Work - !!! see the last post on the link

cheers

Good job,have nearly completed mine and found very little wear in spindles (thank goodness),I didn't remove my floats as the screws are easy to strip,didn't think it was a problem anyway .
What did you do for gaskets under the velocity stacks?,the kits don't have them.
alfa1750 kits fitted very well and have parts included thats others don't,service from HER was great also,she even found a replacement air bleed screw as mine had been broken by PO.
A word of warning for those thinking of doing these carbs,NEVER do up the spindle nuts without locking the throttle cam properly,I learnt the hard way and ended up with a spindle twisted out of line with the rest,took a bit of work to fix .
I found these carbs to be well engineered and pretty easy to do,forget all the BS about part supply as opposed to Webers,I was able to get all the parts I needed and looks like this poster had no issues.....its just the waiting thats a hassle.

[Arts911]

I Have a question. Do all the jets have aluminum washers ? I removed the main jets on mine and they didn't have any. I check another pair of Zeniths and the same .

I didnt even notice a rubber o Ring

I only noticed the o'rings on the air mixture and the injection tubes

[Arts911]

Never mind .... I figured it out