cis heads
 

Hi guys,I,m building a 2.7 with webers and the cis heads have a injection divit in the side of the intake port which the carb gasket does not completely cover,so I,d probably have a vacuum leak at this point.My machinist wants to fill in the divits by tig welding.Does this sound acceptable?Thanks,T.C.

I would use .100 thick aluminium and cut gasket shaped pieces out with the CIS shape on the exterior cut and the center hole cut to the manifolds for the carbs. Then use a CIS gasket on the bottom and carb manifold gasket on the top.

Hope this helps
Tim in Sac

I have a few questions.

First, how are carbs commonly used on a 2.7l, CIS engine? Do the people that have done this conversion use the 2.7 CIS heads?

Next, can 2.4l heads be bored to accept the 90mm barrels and used in place of the 2.7l heads? Would this be the preferred method, or is there some other way to make the 2.7l and carbs compatable?

Finally, what does the 2.7l RS heads look like? Do they have these pockets at the beginning of the intake, such as the CIS heads have, or are they round like the other heads are?

I want to build a 2.7l engine using 40mm Webers and E or Solex cams, and I'm qurious as to how to go about accomplishing this.

Thanks.

PMO makes spacers that will cover the CIS divot, and will thermally isolate the carbs from the heads. They require two gaskets, of course. This is the only right way to go in my opinion. They are reasonably cheap too. If you are going for absolute performance, you should fill in the divit as part of the head porting, but it is not absolutly necessary.

I like the weber/2.7 CIS long-block combination. It's an easy quick way to gain performance without doing major engine work. The fuel milage will go to hell, and you may not pass smog, but neither is a concern for me.

The 2.7 RS heads heads had 36mm ports, rather than the 35mm of the 2.7 CIS 911S heads or the 32mm 911 heads, and the RS did not have the divot of the CIS engines since it had the MFI, not CIS.

Thanks,

JP

Does the 3.0 have those same 'divots' in the port?