Early 2.0 Distributor Performance

dmaddox · 01-30-2021, 07:01 AM

Hello - Upon investigating a starting issue I've been having, I have been going through fuel delivery and ignition to clean/diagnose/etc.. each system.

Upon doing so, I discovered that my early 1968 2.0 (911L) contains a 70/71 2.2 Bosch distributor (0 231 159 008). While the original/correct distributor is 0 231 159 001, the car seems to be running ok once started, with an acceptable power band (although I have yet to really warm up the car and get it into the higher RPM range).

In researching the advance of these two distributors (the 001 and the 008) I found the following:

008
10 degrees advanced at 1000rpm
12 degrees at 1500
14 degrees at 2000
16 degrees at 2500
19 degrees at 3000

001
7.5 degrees advanced at 1000rpm
8 degrees at 1500
8 degrees at 2000
10 degrees at 2500
13 degrees at 3000
15 degrees at 3500

These two distributors advance on very different curves. Using Early 911 Distributors - Carbs-Fuel-Ignition (CFI) - Repair & Sales as a resource, I noted this rather interesting statement:

"Porsche matched distributors to engine and model type as shown in the table below. Some degree of crossover is possible, as is some 'tuning' of the advance curve. But hard limits and transitions are determined by the design of the advance mechanism and are difficult to modify. In most cases, the distributor designed for a particular Porsche model is the best choice."

Now, unless modifications have been done to the 008 that is in my 2.0, I have been running on a 70-71 911T advance curve. Looking at the charts on the website, along with the analysis I posted above, would you expect a degradation in performance going back to the 001, which was intended for the 2.0?

Maybe I am fussing over nothing here, but when others are fussing about the correct "BOSCH" orange in the replacement lens, I don't feel so bad digging into the specifics of a distributor.

Again, I am learning and appreciate any guidance.

Cheers.

SWS911 · 01-30-2021, 07:13 AM

The key to the distributors for each car are the cams. Figure out which cams you have in you engine and go from there. I'm building a 2.4 on an early aluminum case using a 70.4 crank, 2.4S pistons and "T" cams for torque, hence I'll be running a 008 to match the cam timing.

dmaddox · 01-30-2021, 07:19 AM

Cool, I understand. I am new to this car, have receipts going back into the 80's and have nothing in the history or receipt stack that would lead me to believe I have anything other than stock cams to this 2.0. I do find it odd however, that once started and warmed up, the I don't have any missing, stumbling or whatever along the powerband.

jluetjen · jluetjen's Garage

How does the car run at idle? What is the idle speed that you've been seeing?

dmaddox · 01-30-2021, 08:05 AM

I love researching this stuff. Part of the passion I guess.

I would assume / guess that all 1968 911 engines, both for the 911 and 911L, since both 130HP would receive the same cams. Only the 911S would have received different cams (and therefore the 002 distributor).

My engine number "3280124" in an 911L US Market 130HP, should be the same in a 911 or 911L

The PET shows 01/04/06 versions of the cams. However, should be the same?

dmaddox · 01-30-2021, 08:06 AM

Starting is tough/rough, but once warm idles ok, idle speed is 950 at spec.

stownsen914 · 01-30-2021, 11:05 AM

It's possible to have a distributor curve off by a few degrees and the engine may seem to run fine (i.e. not run so badly that it misses or stumbles). But it may not make optimal power.

Trackrash · Trackrash's Garage

The problem with the '70-'71 dizzy is it is set up for smog control.

Those dizzys have a 4* AFTER TDC idle setting. Which is crap for idling. You want something like 7-10* before TDC at idle.

The best solution, IMO, is for you to recurve the dizzy so you have 7-10 degrees at idle and 35 degrees total at 6K rpm. If you understand how a dizzy works you can bend the stops for the advance weights to achieve this.

dmaddox · 01-30-2021, 02:43 PM

Excellent information. I am looking for the correct distributor for now, but if it comes down to it - I will 100% get in there and learn this - or both. Trackrash - thank you.

Would you happen to know if the 911L motor (late 67 build date) would have different cams than say a regular 911 or a 1967 911? The "L" didn't get anything special, motor-wise, right? Just trim bits and brakes/etc..

Cheers,

Dallas

Trackrash · Trackrash's Garage

The L model had the MFI but with E cams. IIRC the L model became the E model.

There is not a lot of difference between the original 911 cams, aka solex, and the E cams. The S cam is much more aggressive. When the T came out that cam was very docile.

Look here. Dougherty Racing Cams Porsche 911, 930 and 964 camshaft profiles

One other thing to consider when choosing an advance curve is the compression ratio. For example the S motors use less total advance.

dmaddox · 01-31-2021, 06:13 AM

I could be mistaken, but my research indicates the L was a carry over from the 1967 911 @130hp. While the 1968 911 was reduced to 110hp and became the 911T. MFI wasn't on the L.

My plan is to source a 1967 distributor, the 001 - and dial in with that distributor to see if that not only solves some of the starting issues, but smoothes out the power curve at all, especially up top.

If not, I'll just put the 008 back in and roll with that. This, assuming everything else is stock on my car.