Venturis

[chris_seven]

34mm Venturis for Zenith 40TIN.

As part of our carb modification mission we have started to make a range of new venturis.

We are making Solex, Weber and Zenith Venturis in any size.

They are made from 6082-T6 and bright anodised.

[classic]

Nice work, they look great

[69Sman]

Nice, and much needed.

[Mr9146]

How about some emulsion tubes to match?

[obrut]

Nice work Chris.

In a recent discussion on Zenith's carb on this board, there was reference to a sport kit for 2.2's that was sold by Stoddards back in the day which purported to effectively remove the factory 'restrictions' on the T motors. It sounds similar to the factory sport kit that were often supplied with rally cars etc.

From the earlier thread:
"I ran the Zeniths on my '70T back in the day. Stoddard sold a "sport kit" for 2.2Ts which was a set of custom machined 34mm venturis, appropriate jets, an E dist rotor (7000 red line), and foam Filtron filters. They recommended a twin pipe sport muffler, but I ran the stock single Leistritz on the street and open megaphones on the track. There were no other modifications recommended aside from venturis and jetting...stock enrichment, left wierd air balance tubes intact, etc. With short gears car ran like scalded rat. Stoddard claimed 35-40 hp which sounded like alot, but the stock venturis were 27mm which strangled the motor, and the way the car ran I tended to believe their claim. The kit was cheaper even then than a pair of Webers. The Zeniths were just fine...many time trial trophies including Parade. If you can find parts, they're OK. Hopefully Ed can help."


What would you recommend (venturi and main jet sizes) to try and do something similar for a 2.4T?

When I do the calcs listed in Bruce Anderson's book (for the equivalent Weber setup) it works out at 30mm venturis, which is only 10% more area over the stock 28.5mm.


I have recently picked up a super original 2.4T that runs like a champ but the thought of it being de-tuned by the factory irks somewhat...

[chris_seven]

We are just about to fit them to a 3.0Sc and a Carrera 3 motor and have all of the relevant jets. We have modified some emulsion tubes and if they work correctly we will re-manufacture.

We have used some bas settings from Webers that we have on another 3.0SC that runs well and has no flat spots and idles correctly and we are looking for a similar result.

The old estimates for setting up carbs is always a reasonable place to start.

I would say a 30 venturi should be OK


Main Jet = Venturi x 4

Air Corrector = Main Jet + 50

Idle and emulsion tubes are harder to figure out but I would start around 60 idle and look at an equivalent emulsion tube to an F3 Weber.

[zenithblue71T]

So, what can I do to get more HP from my Zenith carb rebuild i'm about to undertake? Bigger jets and venturis? E distributor? I have a stock Dansk exhaust and SSIs.

[chris_seven]

We have installed a few sets of Zeniths - mostly on 3.0 litre cars so it really depends on your engine spec.

We are just about to complete our own Zenith Rebuild Kits as I have found the gasket quality on the kits available in the UK to be quite poor and many of the O rings don't fit correctly.

I have managed too source Ethanol resistant diaphragms which should be delivered next week and already have the needle valves , gaskets (made from good quality Klinger materials) Sealing washers and springs.



We have larger than standard pump jets and 34mm venturis available as well as idle jets, main jets and air correctors.

I still have to source the diaphragm for the US based emission control system but we have just completed a 'kit' to delete these parts.

[preS]

chris_seven I am amazed how many parts projects you do and are able to help us w/ better parts than what is average available!

I have not bought from you yet but you are definitely one of my preferred vendors I would contact first.

Richard

[chris_seven]

We are doing the same kits for the 40IDA3C as well and have quite a few other parts ready.



We have a batch of new rocker shafts and have them running in about 5 engines now.

They are made to a very close tolerance.

The steel is 300M and they were stabilised at 580 degC after machining, they were then ground and Nitrotec surface hardened.

Nitrotec is a nitrocarburising process that produces a surface with a hardness of about 1000HV and produces an oloephilic layer.

It is not as hard as DLC but is a surface diffusion based process not a brittle coating and I think is more appropriate and much, much less expensive.

The forging dies for the 906 Rockers are on order and as these rockers don't have any bushing we thought we needed hardened shafts.