Maximum advance for SC 3.0 or ss 3.2

[Gunter]

Would this work for you?
Maximum advance on a 3.0 or ss 3.2 with CIS:
All components like cap, rotor, ignition wires, plugs etc. have to be good; distributor serviced (Cleaned and oiled) the easy way:

Distributor service (Clean and lube) real easy without removing the pinion gear!

Normally, an SC is set to 5 deg BTDC at ~900 RPM vacuum disconnected.
Instead of concentrating on 5 deg BTDC, I set to maximum advance.
In the case of an SC, 32-35 deg BTDC.
On the pulley, calculate the distance to get 32-35.
On an SC, Between Z1 and 5 deg is 5 mm.
To get 33 deg, use a vernier caliper and set it to 33 mm.
Measure from Z1 and mark the pulley at 33 mm.
I used a small chisel to make a permanent mark, along with a small white paint mark.
Warm up the engine.
Adjust RPM to ~900 with vacuum advance/retard disconnected (It may require adjusting mixture and fast-idle screw)
Get the strobe light ready.
Distributor hold-down nut loose/snug.
Vacuum advance/retard still disconnected.
Rev the engine to at least 5000 RPM and move the distributor until the strobe light shows the 33-mark matching the case-seam mark. Let it idle and tighten distributor.
Re-check the idle and tweak mixture and fast-idle screw if necessary to keep ~900 RPM.
Now connect the vacuum advance/retard.
There should be no, or very little, increase in the factory 5 deg idle.
Re-adjust RPM to about 900-950 with the fast idle screw and mixture adjust if necessary.

The above worked well for me (ss 3.2 with 964-cams Bosch '78-CIS)

[Porsche Head]

What was the final BTDC reading after adjusting for max @ 4000 rpm?

Just curious cuz I I think I am at around 12-15 BTDC however I recurved the dist with heavier weights. I found the curve better if I dialed more to start and slowed the curve.

Cliff
SSI/2in2out/7:31 gears/72 body

[Gunter]

Cliff:
It came in around 8-10 at 900 RPM, vacuum connected.
Correction! Wrong vac connection!
No change! The timing is 5 deg w/wo vac connected in idle.
Stock distributor, no pinging, good pull.
Noticably better performance setting it this way.

[island911]

Great thread, Gunter. A couple questions....

What's the CR (compression ratio) of your ss?

What octane fuel are you running?

[Gunter]

9.8 : 1 CR
After Steve's advise, I will use 94 here in Canada and 92 in the US.

I tried different serviced OEM distributors ('78, '80, '82) and found some difference between the '78 and the later ones:
The '78 seems to have a slower mech advance in the mid-range compared to the '80-'82 types and the engine likes the '78 better.
Also, the '78 seems to have a range of about 4 deg more than the later ones.

The engine likes high revs with the max advance method and idles easily; steady temperature.

[Steve@Rennsport]

Originally posted by island911
Great thread, Gunter. A couple questions....

What's the CR (compression ratio) of your ss?

What octane fuel are you running?

I'm glad that Glenn asked those questions,....

91 octane will not safely support using the higher range of advance values of total advance, (especially in hot weather) unless the distributor is recurved to limit mid-range advance to prevent detonation.

Remember,....using your ears as the defacto "knock-sensors" to detect detonation will hurt your pocketbook.

[island911]

I'm not sure if I should start another thread to ask; What's the best way to run flexible tubing from the engine to the headrest? --I joke.

Steve really made the points that need to be made. --If you want to be conservative, and not have to worry about fuel, weather & engine temperature, then use the factory settings. --they did the work for you.

For those of us who want to maximize the bang... posted timing data/settings should include CR, fuel type, ambient temp, engine temp, volumetric efficiency as a function of rpm... ... hmmmm, maybe we go back to the tube routing question.

[Gunter]

After re-checking the connections, I found that factory settings (5 deg BTDC) will get 33 deg total, so, it's 6 or half a dozen.

[Zeke]

Originally posted by Gunter
After re-checking the connections, I found that factory settings (5 deg BTDC) will get 33 deg total, so, it's 6 or half a dozen.

So, this was much ado about nothing?

[Gunter]

Yeah, it seems that the distributors '80-'83 for an 3.0 SC have a total of ~33 deg advance no matter how you set it.
But some people swear by setting it to max and let the idle fall wherever.

If you set it for max 35 deg, you'll end up having 7-8 deg in idle as far as I can tell.

The '78 distributor shows a max of 30 deg (5 in idle) with a slower advance in the mid range which is more desirable?

[911pcars]

Gunter,
How are you determining the maximum advance for your engine? As Steve points out, you can't hear high speed detonation (pinging). IMHO, while the factory spec may be pretty close, only testing on a dynomometer can tell you the specific number for the specific engine tested. And if your engine isn't built to factory specs, then ...........

How about another 2-3 degrees? And, does the factory advance curve provide the optimal advance for that engine speed. See what I mean? Unless tested, the settings are a compromise with, hopefully, a margin of safety.

Sherwood