Deciphering 1970 911T ignition timing specs...

[Tremelune]

I have a 1970 911T with a stock 2.2, Webers, WR5DC+ plugs, Beru wires, and a Bosch 0 231 159 008 distributor with no vacuum. I just adjusted the valves, and now I'd like to do the ignition timing, but I've never done it before, and I'm struggling to find the right specs.

I'm going by this Pelican article:

https://www.pelicanparts.com/techarticles/101_Projects_Porsche_911/23-Timing/23-Timing.htm

These two documents are what I'm using for the "technical specs" Pelican keeps telling me to find:

http://early911nzdownloads.yolasite.com/resources/TD%20Technical%20Data.pdf

http://p914-6info.net/911_Manuals/Early%20911%20Vol_2_Section_TD_Technical%20Data.pd f

They're a bit difficult to decipher, but I've gone down to page STD34 which seems to be correct for my engine ("Type 911 C", under the the 911T section with a 2,195cc engine).

I also stumbled on this thread, where someone claims that a 7-10° retard at idle is preferred (though it would affect emissions):

Marelli and Bosch Distributor Comparison for 2.2L 911T

So. Here is what I think I know:

Point gap - 0.010"
Dwell angle - 38° +/- 3°, 35° ideal
Spark plug gap: 0.6mm
Idle - 5° ATDC, but maybe 7-10° BTDC based on internet chatter.
6k rpm - 35° BTDC

It seems advance at 6k RPM is usually 30° for these cars, but isn't for a 2.2L 911T (according to these documents from the dark ages that ambiguously describe several different engines and models over the year).

Pelican says to test advance at 6k RPM, and it says to do it when the engine is both cold and hot, which implies I'd do everything at operating temperature, then come back the next day and check again...Is that...so?

For dwell, is the expectation that I run the engine, measure, then kill the engine, open the distributor, tweak, and repeat? I have no helper.

Is it okay if my idle speed is off? It seems weird to mess with the carbs before timing is set.

Do I have this right?? Any tips are appreciated. I'm just gonna get my timing/dwell/tach gun and start messing around...I'm still searching for a factory manual for 1970...Currently the car runs great above 3k rpm when fully warmed up, and gets some pops and clicks elsewhere...and really isn't so happy when cold.

[Tremelune]

This is the curve for my distributor (source), but I don't know how to convert shaft speed to engine RPM:

[47silver]

Times 2

[Tremelune]

Aha, thanks! Seems like 35° BTDC is the number after all.

Now I just need to wait for new plug wires, since my coil lead snapped off in my dizzy...

Just...screaming for a distributorless setup...

[47silver]

Make sure you lift the felt pad and drip some oil (123) light type into the center.

[BK911]

Yup. Dwell is a pain.
I measure it first with a dwell meter then adjust by points gap.
Spin engine by hand until points open then Measure gap
then adjust with next size blade up/dn depending if you want to decrease/increase dwell.
Pita but usually one or two tries and you should nail it.
Then set timing at full advance.
Usually gets there 3500ish rpms so no need to rev to 6k.
Then on to carbs.

[Tremelune]

Arright, I'm a bit boggled. I've got my dwell at 35°. I have new Bosch WR5DC+ spark plugs, a new Bosch distributor cap, Beru rotor, oiled shaft, new OEM points, new Clewett plug wires, and my (possibly original, but newly cleaned up) black Bosch coil tested 0.6ohm at the primary and 685ohm at the secondary.

When I go to time this thing, it's pretty jumpy. At 3,500rpm, advance is a fairly steady 30°. When I rev over 4,000rpm the light flashes decrease in frequency by maybe half...When I rev higher, the timing bounces around between 30-35° and sometimes seems to go over a bit. It's very difficult to get a clear reading. I have the light clamped around the cylinder 1 spark plug wire as far away from other sources as I can get it.

After adjusting the timing, the idle is a bit stronger. Seems like it's around 5°, but it's not the steadiest of idles, I must say...There are some pops and what not (possibly even when revving), but it was doing that before. I haven't gotten a chance to mess with the carbs yet, besides cleaning out the idle jets by blasting carb cleaner through them. I haven't driven the car yet.

The only thing I can think of is that the coil isn't charging up enough and it's missing a spark at high rpm, but the pops don't correspond to when the light flashes decrease in frequency above 4,000rpm...I'd be willing to buy a new coil, but it tested fine, replacements are low in quality, and I don't love throwing parts at things...

Before I started, the cylinder 5 spark plug was rather sooty, but the others looked good. Cylinder 4 spark plug wire was corroded, and the others were clean.

Maybe my Innova 5568 timing light is garbage, but...it doesn't seem to be...

Any ideas?

[frosty2]

Mine was a 2.4t and had the distributor recurved and done away with the vac lines.
I was told to set the timing at 7-10 deg BTDC but it would not run properly so I played around and found that if I adjusted it to 7-10 deg above it’s stock setting of 5 deg ATDC
which was 2-5 deg BTDC bingo suddenly the exhaust sounded throatier and the engine
suddenly came to life.

[Tremelune]

Hm. My idle is on the erratic side, and my pulley doesn't have the 5° mark...I'm not sure what I can do about that besides messing with the carbs, and that's a bit dubious as I'm trying to avoid rebuilding them completely...I should probably just do that, but then I gotta do the timing again anyway...

Isn't the redline value more important? This car spends more time near redline than idle...

I could try and get dwell to closer to 38°, but I've read that it isn't all that important on cars with CDI boxes...I'm a fish out of water; I've only ever had fuel injected Porsches, and this is a lot more involved than tuning my MGB!