Zenith Rebuild - My First Carby Project

[johnsonfm3]

Hi Rodoredas,
I thoroughly enjoyed your "how to do it" on cleaning my Zenith 40 TIN
Carby's.
While removing part #26, accelerator jet (injection pipe) from the main carb body it snapped in 1/2 at the waist!!
Any advice on how to remove it?? Perhaps I should try just finger pressure as I was trying to overcome the gasket resistance with a pair of needle nosed pliers...
Thanks in advance,
Fred

[johnsonfm3]

Hi Shane,
To clarify the above, I'll remove the rest of the damaged accelerator jet by using dental tools etc.,or drill it out.
My question is how to remove the remaining jets. Were you able to remove them with finger pressure?
Mine just snapped, not like frankc described above. It was virgin, but perhaps the "O" ring was stuck!

OBTW, my central accelerator pump chamber has no vanes but the two outer ones do.

[rodoredas]

Hi Fred, thanks glad you enjoyed it, it's good fun and I hope you enjoy doing yours. Yes some are tight I seem to remember, spay some WD40 let it soak 10-15 minutes, then try and twist, they should just pull out with fingers or pliers, just take it slow. O-Ring is sure stuck. I wouldn't drill. Let me know how you get on. Looked at some of the non-published photos my accelerator pump same.
cheers
Shane

[Einar Irgens]

Hi, all.

I am currently working on my second set of Zenith TIN 40 carburetors, and stumbled upon this thread while searching the web for a decent rebuild kit. Impressive presentation by rodoredas! I however have a question. When overhauling the first set about 10 years ago, I reused all the jets. Is this risky? Should any jets or nozzles be replaced by new items just to be sure? Do they wear over the years? Are the ones with glass balls inside more prone to malfunction?

I also have one piece of advice. Before dismantling a carburetor that has not been apart for a few years, make sure to lubricate the idle mixture and air screws also from the inside. If you look inside the bore underneath the butterflies, you will spot tiny holes where the air/fuel enters the air stream. Fill these with WD40 or similar and leave overnight before attempting to remove the screws. When adding torque, the idle mixture screws in particular have a tendency to break at the smallest diameter.

Originally Posted by rodoredas

[Turbo_pro]

Cool thread

[911 SLANT]

On my Zenith 40TIN. 165 mains, 185 air correction and 60 Idle air. 34 vents. Running on a 2.7 with 964 cam grind, ported heads, 8:5.1, SSIs and GT3 MK, 7:31 on 915. MSD ignition and coil. Car spats at 3,000. Idles nice at 900rpm. No issues with idle. Will pull at take off up to 5000 . Cruising at 3000 spats. Cruising at 3300 at 70mph it purrs. Should I leave it or figure out why its spats at 3000?

[rodoredas]

Hi 911Slant
I had similar case when doing test drives with various jet configurations - i'd suggest increasing idle jet and or adjusting mixture screws out a fraction - but just do one at a time and see if there's any change.
cheers

[DaveO90S4]

Hi all,

Thanks to all who have posted - great for someone like me who has decided to get to the bottom of their Zenith 40 TIN carb problems.

Not wanting to hijack this thread - but just to say I'm running these carbs on my modified 2.7L Chev corvair aircooled 6 in my Porsche 914 in Brisbane, Australia. Have had the car and carbs to a number of so-called 'experts' and have been disappointed with their work, so have decided to do it myself. Yesterday I removed and plugged the 'auxiliary air enrichment circuit', as seems to be the considered wisdom. Am adding phenolic spacers and am making gaskets above and below to suit.

Running 180 air corrections, 55 idles, 30mm venturis, 135 mains. Runs much too rich, especially at cruise (11.5 AFR), otherwise runs well. I have a range of alternative jets plus a set of 34mm venturis, synchroniser tool, float level gauge, repair / tuning manual, and have been scouring the net for info, and hope make use of this 'at home' time this week to get the carbs back on and see if I can tune it.

Am very interested in other peoples 'best' jet and venturi combinations on (say) 2.4-2.7 L engines.

Again, hope this is not a hijack!

Cheers
Dave
Brisbane, Aus

[rodoredas]

Hi Dave,

good to see another set of Zeniths being put to use. From memory my latest config is idle 57, main 145, air correction 180, venturi 34mm (cars in storage and I can't get to them to check). I'd be upgrading venturi to 34mm - I reckon you need more air. At idle 900rpm I have approx 5Kg/Hr on each cylinder, use the bypass screws to adjust.

Get your hands on the Performance Orientated Weber Tuning document, while it focuses on Weber it's relevant to the Zeniths.

Interesting setup you have anyway with that Chev Corvair flat 6.

cheers

[DaveO90S4]

Hi Shane, thanks for response. And thanks for putting Greg and me in touch with one another.

I agree with your thoughts re reverting back to the 34mm venturis - I did that last night. My thinking was it ran well with 34 venturis when I first used it and before I was persuaded to put 30mm venturis in it.With the 34mm venturis there should be somewhat less air velocity and vacuum pulling the air fuel emulsion through the jets at a given rpm, so that will maybe / hopefully lean it out. I had nearly fixed the transition stumble with the 34mm venturis, and I reckon if I go back to my last 'best' jets for the 34mm venturis I shouldn't have to then make too many more changes to get it right, and hopefully with decent AFR through the rev range.

I think if I could get 13.5 at idle and cruise and say 12.5 at WOT, with good progression, I'd be pretty happy.

Cheers

DaveO

[rodoredas]

Hi Dave

great, I reckon the two of you will sort it out, Greg knows what he's doing.

What tool kit are you using to measure AFR?

Let us know how you get on with tuning and what your final setup is.

I'm hoping we can make it up your way later this year so would be good to catch up with both of you.

cheers

[DaveO90S4]

Hi Shane,

I've installed an O2 sensor in each side, and a pair of AFR / lambda gauges on the dash, so I can monitor both left and right banks. As an overkill I also had one bung per exhaust 'log' so I could monitor individual cylinder AFR if necessary. A bit of overkill really I think.

Carbs back on the engine, may try starting it tomorrow once I've pushed it out of the shed and have fire extinguishers at hand - just to be on the safe side.

Cheers

DaveO

[rw7810]

Somehow I have misplaced/lost an injector tube. Anyone happen to have an extra?

[Hi_Fi_Guy]

You can purchase almost all part for the carbs if needed. Parts Klassik online and alfa1750 on eBay both have just about everything you could want.

[stephers]

Just talked to ************ today out of stock on the acc pump nozzles, not sure when they are getting more

Thanks, Rick