Zenith conversion
 

What are your thoughts on converting a 73.5 T from CIS to Zenith carbs? I obviously have a 2.4 engine. I would be using something like E or S pistons with this. Has anyone bored out the Zeniths for more flow? What would be the best combination to provide decent low end torque and reasonable HP (dont need to rev like an "s").

I used zeniths on my 2.7 and they work great but you will need venturies and jets. I think weber venturies will fit and the jets your better off doing yourself . Buy a set of jet gauges and some small number drills to set up your jets. You can save some time and call MM as they have all you need for your conversion. They are sometimes hard to deal with but there parts a re inexpensive and of good quality. I would not have them do any work for me however. Just ask the other members

Ben

77 911 3.0
75 914-6 2.7

Depends on the price of the Zeniths.....personally I would consider some new PMOs......2900ish for a new kit.....includes intakes, plumbing and air cleaners.....they have bearing in the throttle shafts and a warranty. You never know what you are getting when you buy used.

According to Bruce Andersons Performance Handbook the venturis for a 2.4 T (2341 cc) should be 31 and throttle plates 34 to 39 mm. I think the stock Zeniths are 27 venturis and 40 throttle plate so I am not sure why everyone dis's the Zeniths as they seem to be sized appropriately. I know that there is not the level of support that Webers have but you can get everything for the Zeniths for about $500 on ebay. Webers are typically 3x that price.

The ROW 72-73 911T had Zeniths not MFI or CIS so you may keep an eye out for some Zeniths from those years.
Differences between 2.4L and 2.2L were:

Venturies 28.5 vs 27.5
Main Jet 120 vs 115
Air Correction 190 vs 185
Idle Air Bleed 155 vs 140

Hope this helps!

Andrew M

I'm not ragging on Zeniths,,,,,just used carbs in general. I would make the same comment on used webers...