Clearance can be an issue but high lift long duration cams lobes cause a less than smooth intake air flow which flops the air sensor around jacking with fuel delivery. CIS is the limiting reason

Best I can remember there is a relationship between the intake and exhaust lobe configuration on the stick for the SC cam that the 964 cam follow pretty closely, even though they have more lift and more duration. This relationship keeps the air flow steady.

Continuos flow of vacuum is a good thing with CIS. Radical cam....get some PMOs.....

Dudes, if you haven't done the mod STFU.

My SC has reground cams to 964 spec. It's a 79 ROW SC, so it has the larger ports and runners. It also has later 9.8:1 pistons and cylinders along with SSI's and a Dansk 2in/1out muffler. It builds speed like a freight train from 3000 rpm all the way to the redline.

Bob Kontak hit the nail on the head. The CIS is the major limitation whe it comes to cam grind. You need smooth air flow for the CIS to deliver air properly. If you eliminate CIS, then valve clearance becomes an issue due to the dome pistons required with CIS.

Thanks all for the feedback.

Now I'm considering several options:

1. U.S. spec CIS with 964 grind, 9.8/10 to 1 pistons, raise displacement??

2. Euro spec CIS w/matched heads, 964 cam, 9.8/10 t0 1 pistons, raise displacement??

3. Motronic, any cam, chip, 9.8/10 to 1 pistons, raise displacement??

4. ITBs (I know zero about), any cam, 9.8/10 to 1 pistons, raise displacement ??

5. 3.6 motor + new exhaust

6. 3.6 Varioram + new exhaust

Of these options, which is the most 'Bang for Buck' and which can be done in logical cost effective stages as I can afford?

Please discuss

Biggest bang for the buck would be to install the 964 cams with what you have.

From there, go right to the 3.6 motor because the bang is so big.

ITB's and P&Cs new are very expensive and buying both would put you in range of the 3.6 motor.


Here's one for example:

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Thanks Bob Kontak and the rest for the advice and info.

Seems like the most sensible is the current motor, 964 grind and a few other upgrades at rebuild.

Then save for the 3.6 + rebuild .