Posted in the rebuild section Maybe the wrong place Carb Conversion Newb Question
 

This is really about saving a wrecked but rust free factory 914-6.

I'm new to the 911 engine. I was able to purchase a 1973 2.7S engine with CIS. I would just keep the CIS as I am familiar with how to tune and repair it. I have done a couple 928 euro spec "S" builds but I'm installing the engine in a factory 914-6. The original engine is long gone.

Believe me if I could keep the CIS I would. I like it but In order to use the CIS I have to cut the engine lid latch off and move it. the plenum interferes with the latch and I don't want to modify the car in any way so I want to change to carbs.

On to the questions already...

I have a set of factory cabs from a 1972 2.4 911. I thought I read someplace there is an issue with lining up the intake manifolds from the CIS setup to carb manifolds.

Is this true? If so what gaskets aid in matching up this issue?

Second: Can I re-jet these carbs for the 2.7S? What jets are recommended as a base line?

Third: Can I use the F.I. cams? I assume these are low lift long duration for low intake pulse.

Fourth and final: If I MUST change cams is there a low cost solution for a sporty set of cams?

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1) CIS port shape need a manifold and insulator with extra metal to properly clamp the gaskets. PMO sells this.

2) CIS pistons don't allow wild cams. The dome doesn't have deep enough valve reliefs. 964 cam is kinda the limit. To run a sporty cam, you'll need new pistons like JE.

CIS cams will work fine with carbs. They just can't flow as much. So no problem there. Ran CIS cam for 5 years. New cam means refreshed rockers.

Carbs for a 2.7 will like larger venturis verses a 2.4. In order to figure out what you might need, you'll have to provide more info on the carbs.

Probably should disassemble and clean first. Then measure the Venturi diameter, and note the size of the jets you have.

Who knows, maybe someone already opened them up to flow more, and now they are fine for a milder 2.7.

Great info guys! I'm not ready to start on the engine yet. I have a chassis to restore first. But I am working in that direction. I'll start with sourcing intakes.

Thanks for the help

Here is a good baseline Weber setup for 2.7 CIS:

32mm Main venturis
135 mains
F26 emulsion tubes
180 correction
55 idle

regards,
al

Thank you, Sorry about cross posting fellas... Great info from the brain trust here!

Nice car, apart from the dimple in front.