The nitty gritty of 2.2T ignition timing...

[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/techart.../23-Timing.htm

This is what I'm using for the "technical specs" Pelican keeps telling me to find:

http://early911nzdownloads.yolasite....cal%20Data.pdf

This document is a bit difficult to decipher, but I've gone down to page STD34 which seems to be correct for my engine.

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

http://forums.pelicanparts.com/porsc...2-2l-911t.html

So. Here is what I think I know:

Point gap - 0.012"
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 like the dwell angle and breaker point gap are related...What's the better way to adjust/measure? 0.016" is specced for the Marelli, but only angle is specced for the Bosch...I pulled 0.012" from the Pelican article.

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 tomorrow...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.

[edmayo]

From the Porsche shop manual for 1970. Dwell 38 plus or minus 3 degrees. Point gap .010" or .25 mm. Idle timing 2 to 4 ATDC. 6000 ,33 to 35 degrees. I take the distributor out and set gap on the bench. All this for 008 dist.

[Tremelune]

Hm. That seems to contradict some of the numbers I was confident about in that technical doc...I wonder how I can reconcile those discrepancies...

Don't you have to set the gap/dwell more than once? Like, isn't it common to set dwell, set timing (which changes dwell), then go back and reset the dwell...then the final timing...

[edmayo]

Dwell changes timing, timing does not change dwell.

[Tremelune]

Oops, I may have read you wrong...Looks like 35° advance at 6,000rpm is a good bet. Let's see if I can hit it...

I was reduced to looking at stickers for sale...

[Tremelune]

Welp, it looks like I have bigger fish to fry...I went to replace my cap and rotor and wound up snapping the coil lead off inside...Cylinder 4 lead was corroded...I think that's the wrong rotor, too...

[edmayo]

That's a non cut-out rotor, so yes it is wrong, it will work, just no over rev cut-out. Yep, that all looks pretty sad.

[Tremelune]

I got a new cap, rotor, points, and a set of Clewett wires...I thought about getting a new coil, but I've read they're all junk and it seems like mine is good.

I'm just trying to do a basic tune-up on this thing...I don't want to spend myself halfway to a crank-trigger COP setup before my third tank of gas in this car...Oh well, as long as it runs better when I'm done!

[66S]

Trouble with low speed running means you should check your idle jets for blockage.

[teenchy]

I thought about getting a new coil, but I've read they're all junk and it seems like mine is good.

If yours is good, of course keep it but you may wish to keep a spare on hand. Many folks have had success with the Partsklassik coil; I've had one for two years with no issues. https://www.partsklassik.com/p-1586-...tsklassik.aspx