Carburetion & Injection

Sales FAQs

1)  Will the PMO carbs fit my Zenith or Weber manifolds?

Yes. All the bolt patterns are the same. Naturally, 40 mm carbs are for 40 mm manifolds, etc.

2)  Will the PMO carbs work with my CIS cams?

Yes. The early CIS cams (73-77) are limited but still allow the carbs to produce more horsepower. The later CIS and Motronic cams (78 and later) are actually excellent cams for carburation.

3)  What about my exhaust system?

The early style exhaust through 74 is excellent. From 75 on an early style exhaust, such as the SSI heat exchangers, is a necessity. The size of the exhaust system is extremely critical. If headers are used, we recommend 1-1/2 o.d. through 3.0 litre and 1-5/8" o.d. on 3.2 and up for street cars.

4)  What about ignition systems?

The stock CDI ignition systems will generally work through 77. The early cars (65-68) will need to add a CDI ignition. From 78-83 the distributors need recurving. Check with Barry at IAE. 

5)  What about my air conditioning and power brakes?

Provisions for both are included in the kits. On the 50mm PMO kits, air conditioning is not an option because all manifolds for the 50mm carbs are tall. The exception is if a whale tail is installed; then the 50mm carbs can be used with air conditioning.

6)  I have PMO watershield air cleaners on my Webers (or Zeniths). Will they fit the PMO carbs?

Yes, except for the base plates. We will include new base plates at no charge when PMO carbs are purchased.

7)  What kind of performance increase can I expect?

This depends on the condition and type of engine. PMO carbs will outperform Weber and Zenith carbs. The increased performance over mechanical injection is usually the result of the mechanical injection running too rich in the midrange (which is almost always the rule). The CIS and Motronic engines need changes in the ignition and exhaust systems for the PMO carbs to work properly. When these changes are made, substantial increases in horsepower are common. Full-on race engines frequently achieve 100 horsepower or more per litre. For instance, George at Midwest Eurosport reports 320 horsepower from a 2.8 litre race motor on their dyno. This engine runs 46mm PMO carbs.

8)  Are spare parts and rebuild kits available?

Yes. The PMO carbs will never have to be rebushed because they have ball bearings on the throttle shafts.

9)  What parts are interchangeable with Weber?

We manufacture all the parts except we use Weber jets, floats, and viton float needle valves. To fine tune the idle circuit, we manufacture the idle air jets.

10)  What kind of Weber jets does the PMO carb use?

The same as the IDF Weber. The main jets, emulsion tubes, and air jets are the same for the Weber IDF, DCOE, 2 bbl 48 IDA, and the PMO.  PMO carbs use the IDF idle fuel jets. As already mentioned, the idle air jets are manufactured by PMO.

11)  What is included in the kits?

Everything needed. Please check our question and answer sheet and check-off list seen elsewhere on our website. We make over fifteen different 911 manifolds to properly fit the PMO carbs to your engine.

12)  Are people happy with PMO carbs and conversion kits?

Yes!  See our list of Testimonials.

13)  How do I order?

See our Purchase page.