emcon5

Cross Posted from Pelican

82 911SC, rebuilt at 111K miles due to excessive oil consumption, has 115K on it now.
98MM Mahle Cylinders with RSR Pistons, measured at 9.8:1 CR.
Cam reground to 964 profile by Elgin.
Twin plug with Rennsport 964 distributor conversion, 2 Bosch CDIs and coils.
ARP rod bolts, 993 steel head studs.
SSIs with a Dansk muffler.
Stock CIS w/ Lamda system.

I have lots of torque, but I think my small intake runners and ports are hurting me up high.

Any feedback would be appreciated.

Tom

jetskied

I'm no engine expert, but it looks like the fuel is enough. It may need more air. The only solutions I can think may be to try a enlarged throtle body. Other solution may be too costly like ported heads, EFI conversion or Webbers.

DGaunt

I was under the impression that CIS would not tolerate a more aggressive cam that the OE profile due to back pulses interfering with the eh sensor plate. Was I misinformed, or is the 964 grind compatible? I thought you had to go to carbs to exploit better cams?

id be very interested in knowing how far Rennlisters have discovered they can go with CIS as the cost of changing the CIS system is beyond my budget.

emcon5

CIS cannot tolerate a cam with a lot of overlap, but there are more aggressive grinds out there which will work. It is generally accepted that Webcam's 20/21 grind is as far as you can go with CIS, and have it run right. The 964 profile is an improvement over stock, but not as agressive as the Web grind.

Tom