Zenith carbs on 2.4 engine

[iolguy]

Any input on using Zenith carbs on a 2.4 L engine with 2.2E pistons? I was going to convert my 73.5 CIS engine to MFI and bought a complete 2.4E MFI unit. Since then I realized it will be a chore to put the injectors into my heads (hole is there but it needs threads). Additionally, I would have to get the left heat exchanger with the heat pipe for the MFI thermostat. Just a lot of little things to do. I have the option of trading out Zenith carbs for the MFI unit (seems to be an easier task). Anybody used Zeniths on a 2.4L?

[Henry Schmidt]

We have used Zenith carbs on everything up a 3.0. The problems you will run into are:
Poor jet selection. We used jets from the Solex 40 P11 (365 & 912) and jet drills.
No venturis. We use modified Weber venturis
Lean running and pore tuning when decel device was left in place. We removed it and plugged the holes with allen set screws.
When all these modifications are performed the carbs work as good or better than Webers.
However I would recommend a new set of PMO's.
Or of course the MFI is my first choice.

Time Certs in the heads will work to install injectors and the Supertec Enrichment devise will eliminate cold start and heat riser issues.

[304065]

What is the Supertec Enrichment Device?

Does it involve going to the Getty Museum?

(seriously, I have a 71E with disabled cold-start as I am allergic to fire, would be interested to know what this is.)

[Henry Schmidt]

Supertec Enrichment Device is a cable operated mechanism that replaces the thermostat on the MFI pump and works so well that there is no need to squirt raw, unmetered gas into the injection stack on cold start. It is my theory that this spray does more harm than good. It (the spray) washes any dust that accumulates in the stacks into the engine and the gritty mixture also causes premature wear on butterfly shafts and bushings. Comes as a complete kit but requires some talent to install.
It's pricey but worth it.

[304065]

Henry,

Thanks for the explanation and photograph.

Is this similar in principle to the 2.0 MFI system that used a second solenoid to move the rack? Do you have any clients that have converted a 2.2 MFI to the solenoid system?

[Henry Schmidt]

I have used the second solenoid system on pumps before we made our enrichment device and the problem with it is that they are full on or full off. No partial setting. With our system the drivers sets the amount of enrichment and duration of enrichment. I'm not saying Porsche owners are control freaks but "I want a knob". If you live at high altitude you can actually adjust the mixture from inside the car.

[andrew15]

Actually, Porsche used Zeniths on 2.4L engines outside of the US. I'll dig out some information and see what their specs were

AM