2.7 CIS on a built 3.0 (now 3.2)?
 

Hi there. I wanted to ask some experts here regarding my engine upgrade.

I currently have a (fairly) stock 2.7 CIS engine in my '77S. I plan to replace it with a built 3.0 (that now has a displacement of 3.2).

Will I be able to use my CIS from the 2.7? Has anybody done this? Will it fit? Will it need to be modified at all (to provide adequate fueling)? What am I missing?

Thanks in advance for sharing your knowledge and experience.

More displacement = needs more fuel.

Unless you're a cis mad scientist

Nope

Compare with the Porsche spare parts catalogue for differences. Any CIS is completely customized on the engine. They vary in several details. In general I tend to say it's basically possible but to be on the safe side I would purchase a complete set of a CIS for exact that type of another engine and overhaul this. Some people fit carbs on these engines and selling the CIS system for cheap money. Any Porsche engine has a engine code saying like 911/xy or 930/xy like mine 930/16. Refer to that engine code when purchasing another CIS for the engine.

In general the CIS is able to feed any of these engines. The 3.0l engine is only 10% bigger than the 2.7. So this should also be possible in general.

Check out https://cis911primer.com/home.html to get a first impression on what they may differ in vacuum lines, changes for emissions etc. I know that the throttle bodies may differ and of course the fuel distributor, sensor plate housing as the main concerns. Also the WUR is quite important on that. The intake runners, fuel lines, ,thermotime switch, sensors, etc. may be equal. A main concern is whether the new engine is a lambda controlled. Then it's way more difficult. What type of engine will the new 3.0 be? Why should the 2.7 be replaced? Is it bad?

Thomas

2.7 CIS is sized for 35mm ports.
Doesn’t fit well on early 3.0 heads or 3.2 heads.

Definitely won’t flow enough air /fuel for a 3.2.

Barely good enough for a 3.0.

My stock big port 3.0 gained 20HP just by switching to a 3.2 manifold. Using aftermarket ECU


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I really appreciate all the feedback and sharing of your knowledge. Thank you so much for taking the time to help me out!