911 sc ignition timing curve

[scott.k]

Hello,
Does anyone have an image/diagram of a 1980 911 sc stock ignition timing curve, or the idle and max rpm degrees would help too. Also, any diagrams of a modified sc timing curve that you are using would be useful as well. This is for an msd 6530 timing map.
thanks
scott

[psalt]

scott,

The factory spec for a US car is 5 BTDC @950 rpm (vacuum disconnected) and 19-25 BTDC max @6000 rpm. Far from ideal for a hemi head with domed pistons and reflect the factory's decision to increase compression and retard timing and still stay safe on 87 CLC octane. On race gas the ideal timing would be somewhere in the mid 30's BTDC. My advice would be to start with 8-10 BTDC at idle, 26 degrees max, and try advancing from there if you have higher octane fuel.

[Gunter]

scott,

I am no friend of MSD, I like Bosch CDI.

Has the distributor been cleaned, serviced and the curve checked?

Distributor service (Clean and lube) real easy without removing the pinion gear! - Pelican Parts Technical BBS

+1 what Paul said but with a question:

Paul,
Do you still recommend to disconnect and plug the retard vacuum permanently on the distributor for the US SC's with Lambda but leave the OX sensor connected?

[psalt]

Yes

[bsimonson]

I have a US 1980 SC but the engine was rebuilt by a PO with "95mm 80-83 Euro" piston/cylinder (930 103 983 01) so I guess it has a 9.8:1 compression.

I use 95 octane fuel.

How much advance would be good @idle and @6000 rpm? Same as the recommendation for Scott?

BR, Björn