CIS Piston "Swirl"

[The Watson]

I have read where the "swirl" on CIS pistons creates the needed turbulence to better atomize fuel since the CIS system lacks in that regard. Makes sense. So when I move to a JE piston, is has protrusions, but not the same swirl. Any "on the ground" info out there as to whether JE or other aftermarket pistons work well with CIS? I was leaning towards keeping my CIS, but this is a factor in that decision.

[Flat6pac]

The JE s work well in the CIS
Bruce

[BURN-BROS]

It's not for "swirl". The dome is placed in order to push the compressed mixture towards the spark plug. It is meant to provide a cleaner burn and requires less ignition timing.

[Bob Kontak]

Originally Posted by BURN-BROS

It's not for "swirl". The dome is placed in order to push the compressed mixture towards the spark plug. It is meant to provide a cleaner burn and requires less ignition timing.

Good info. I do remember on my top-end job the piston tops had an eyebrow sliver with no carbon deposits on them. Hope it has something to do with pushing the AF mixture away from the sliver.

The Watson needs to figure out if a distributor re-curve is in order and bank on using higher octane gas.

Do all the pre-SC CIS cars run "regular" octane gas?

[BURN-BROS]

Originally Posted by Bob Kontak

The Watson needs to figure out if a distributor re-curve is in order and bank on using higher octane gas.

I do not recommend a recurve for a 3.0 liter while retaining CIS. The system is designed to run lean and the timing requirements for a 90cc combustion chamber is more than the available fuel could take.

Originally Posted by Bob Kontak

Do all the pre-SC CIS cars run "regular" octane gas?

I think they do. Compression was lower and the combustion chambers are 25% smaller.