Gunter

My 1980 SC has "B" group cams but standard CIS (No Carbs!) It runs very lumpy in idle but very good above 3000 RPM. I have to set a rich mixture and cannot go below 1400 RPM in idle, or else the engine coughs. I want to change back to regular SC cams. What are "B" group cams? How many groups, or cam grinds, or specifications are there? Thanx. <img src="confused.gif" border="0">

Geoffrey

Turbo Group B cams have an intake duration of 237 degrees and .374 inches of lift and exhaust duration of 220 degrees and .339 inches of lift.

Gunter

Thanks for the specs. Has anyone out there had similar experience with these cams not working very well with standard 3 liter and regular CIS?

Steve Weiner-Rennsport Systems

Gunter:

FWIW,....Group B cams would not be the cams of choice for any naturally aspirated CIS car. These simply do not run very well, as you have noticed.

The lobe centers on Grp. B cams are 106 deg and 2.7 CIS ones are 116 deg. This is what accounts for the intake tract reversions that upset the sensor plate. This creates the poor running below 4000 RPM. Even SC cams have 112 deg lobe centers and these would be the cams of choice in most CIS cars.

I might suggest replacing those with SC ones to restore the low-to-mid range power and drivability.

We no longer use Group B cam in Turbos and these were designed and intended for those cars exclusively.

Hope this helps,