2.7 Ignition timing?

[ClickClickBoom]

Hey,
I have a 1975 911S with a 2.7. I slapped a Pertronix ignition points replacement in with no drama, started right up and idled nicely. Idle was a little low so I decided to put the ole timing light on the issue. Timing was set between the "Z" mark and the first timing mark on the pulley. The FSM states that O degrees BTDC, when I set it to that mark it doesn't want to run. I know I can run it to 6000rpms and set the 35 degree value specified in the original FSM. My question is the Red FSM is for the earlier engines and I also have the Grey FSMs for the 1974 thru the 1980s models. If I set it at 6000 rpms will I be on the mark? Any advantage to disconnecting the vacuum retard?
I have used the Pertronix on several other cars and loved them. I know this one will rock once I get the timing locked in.
I also have SSIs, stock intake and cams, and run 91octane.
Any bright ideeaers?
Thanks
eric

[James Brown]

if everything is stock, you might have a vaccum leak. but, like mine, I set it where it runs best. +- a few degrees at idle shouldn't hurt. Thats a CIS car, right?

[2.70Racer]

From the factory service manual: 5 degrees ATDC with the vacuum hose connected.
The vacuum is to retard the timing for smog purposes.
I also found my '76 2.7 CIS ran better with the vacuum hose disconnected and blocked, ignition timing set 4 or 5 degrees BTDC, and the mixture slightly richer than called for to pass smog.
I would spend a day or so connecting the smog pump, adusting timing and mixture to pass smog every 2 years in Albuquerque.
I now live in a smog free county. No smog or smog tests.
Run my carbs, cams, and higher comp pistons.
It's a track car today, rarely on the street.
It wouldn't pass smog in Kalifornia.

[RoninLB]

I did same as Doug when I ran CIS and stock dizzy

5 BTDC and vac retard disconnected... and slightly rich, I think to 3.5

[carrera turbo]

hello
i normally set the timing at 5-6 k to full advanced per spec for motor, then i see how she runs at idle and adjust the CO% to spec and then adjust it to make car run smooth, i pretty much ignore the at idle timing and go with the full advanced number for safety, i watch to make sure the advance mech. is working and dial in the timing from there. I'm sure there are others who do it different but i have been lucky so far with this method.

cheers ed

[ClickClickBoom]

Thanks guys,
I will delete the vacuum hose and set it for 35 deg at 6K. Comforting to know that these motors are well....... motors, and respond as such.
eric

[ClickClickBoom]

Hey,
Capped the vacuum line to the dizzy, timed it at 6000 rpms, 35 deg. Wow, these cars really like proper timing, it still hits at 3500 rpms, just harder than before. It would seem that the PO's shop set the timing to some mysterious value to run good down low in the rpms. At lower rpms the idle was a little erratic, hitting the mixture and fiddling with the decell valve. Got a nice stable 900 rpm idle.
eric