Diff between Early and late SC intakes

[CEO]

I need to know what all the differences are between the early and late (lambda) Intake systems. And why did porsche go to small intake runners on the late style?

Any info would be great.
Regards, Kenneth

[JackT]

I read somewhere, can't remember where, that the smaller intakes worked better with the higher compression of the late model SC's.

[jluetjen]

From what I can tell, my theory is that the smaller intake diameter may have improved low engine speed running (possibly a pollution improvement) by keeping the intake gas speeds up. I haven't seen any data that would suggest that it hurt the performance at all on the 3.0s.

I'm guessing that increasing the CR could have an offsetting affect on any drop in efficiency at higher engine speeds resulting from the smaller intakes, as well as improved the part throttle performance.

[Bill Verburg]

As John said the smaller ports & runners contribute to low speed torque and throttle response by keeping gas velocity up, this also sharpens and enhances any vacuum signals which might be used.

When I raced MX I had several sets od cylinders(2srk ports are in the cylinder walls)c, some with bigg high hp ports and some w/ smaller toqier ports. The track and track condition determined which was used.

[dd74]

Originally posted by Bill Verburg
When I raced MX I had several sets od cylinders(2srk ports are in the cylinder walls)c, some with bigg high hp ports and some w/ smaller toqier ports. The track and track condition determined which was used.

So did you have to change heads along with the CIS depending on the track?

[Bill Verburg]

2 strk heads are just a lid for the jugs and a place to screw in a spark plug, single cyl. 2strks are very simple devices

[CEO]

The info I have is that the 78-79 SC used 45mm runners and ports and the later ones 39mm runners and ports.
Noah where did you get your information at.