No
The distributor has both mechanical and vacuum advance.
As for the vacuum advance, because we use a dual vacuum pod we get a dual action.
With vacuum we get 3 degrees of vacuum advance.
At zero boost/ vacuum we get 0 degrees of vacuum advance.
With booth the advance can starts to retard. The more boost the more the retard until it reaches 2 degrees of dist. retard.
Now, the mechanical advance works independent of boost. It only cares about RPM. The higher the RPM the greater the advance until it reaches full advance about 12 degrees @ around 4500 RPM.
We then set the dist. at 30 degrees no boost.
That is about 0 degrees static.
max advance about 30
0 at idle
20 degrees @ full boost @4500
This allows us to run 1.0 bar of boost, no intercooler, street gas with 7.5 to 1 comp. with no detonation.

PS: the horse power and torque is great.

Henry, it was very kind of you to give me some of your time today over the phone. Your suggestion of using the 3.3 turbo pistons and cylinders over the 935 pistons in my 3.0 cylinders has me rethinking and going in that direction. Could you please post the rod modifications for me with the bore and offset with explaination, my notes got the best of me.

We have installed 3.3 (97mm) pistons on the 3.0 crank many times in the past few years. But it's not that easy.
Some back ground.
The 3.3 has a longer stroke but a shorter rod. To make it all fit and maintain the same overall engine dimension Porsche raised the pin location in the piston. (pin height).
The stroke is 4mm more, but the rod is only .8 mm shorter.
That means they raised the pin height 1.2 mm because the stoke made a 2 mm difference at each end.
Here's what you do.
Remove the old pin bushing.
Off set bore the 3.0 rod end to fit the 3.3 bushing. Remembering that we are trying to make up for the different wrist pin location, set the bottom of the new hole at the bottom of your existing hole.
This will give you almost 1/2 of the rod length you need.
If you want all the the deck height back you will need to make a bushing that has a 3 mm larger OD with a 20 mm id and install that bushing in the 3.0 rod. Now you must off set cut this bushing .5 mm. This will give you the proper deck for normal installation. When you're all done your rod length should be 2mm longer. On most Porsches longer rods are better.
Higher compression pistons, no CE rings and longer rods, all good.

Henry thanks for the the info, it seems like a lot of work but probably not in the hands of a competent machinist. If I were to stay with the same displacement then the 935's with the stock re-plated 3.0 bore would be the cost effective solution and produce an engine similar to your 74 project in this thread. I will stay in touch with which way I choose to go.

Henry, don't want to bug you, but did you ever get a dyno sheet for this project?

The car is out of my control, but if the owner chooses to get it dynoed and then release that information to me I will gladly post it here. Until then, he's driving the wheels off the car, as he should.

Henry,

Slightly off-topic I know but what engine modifications do you recommend for '76/77 3.0 Liter 930 Turbo?

TIA

Henry, I didn't mean it like "go out and get me a dyno test for this motor pronto!!" I just noticed you said "no dyno sheet yet but what fun" on the first page, and I was curious. I think this and the 2.8SS are now 2 of my favorite 911 engines running around.

Now, how difficult is it to Motronic-ize a 3.0T like this? I was thinking of perhaps a non-IC, twin-plug, Motronic, SC-based engine with 3.3T p/c...a 3.1T beast!

It would be no different than building one with an intercooler except you would not have to fabricate an intercooler.
It seems like converting a 3.2 to a 3.1 might make more sense.
Either way great fun is in store for some one who builds this engine.

It depends on what you are looking for.
I like increasing the compression ratio slightly, porting to 38, SC cams (even better than 964). If the engine is coming completely apart, a 3.1 conversion makes sense.
Twin plugging on a non intercooled turbo is also a good idea.

The magic to 3.1 (70.4x97) is that the pistons set are readily available and when the rods are lengthened to use the 3.3 pistons, the engine spins with greater ease.

I like the idea of a non-IC, twin-plug sleeper, but with Motronic. Would it be good to use 3.2 heads? I kinda think so...I'm thinking you are right on using a 3.2 as a base instead of an SC...The 3.3 p/c did seem like the "magic" combo when I first considered them (and recalled your descriptions of rod length:stroke and the optimization thereof)! Now, how much more difficult/expensive is it to do a Motronic-based turbo, with the plumbing, etc.?

Great info, but what about the 6 bolt crank as it uses 2.7 rod?

If you want all the the deck height back you will need to make a bushing that has a 3 mm larger OD with a 20 mm id and install that bushing in the 3.0 rod.

This is the part that concerns me, make a bushing.
are there bushings available that can be machined to these spec's or are there after market bushings available for this modification, or do I have to start a foundry in my garage.

Any good automotive machine shop can order custom bushings.
If you have trouble, let me know.

As for 2.7 rods, they are the same as 3.0 rods in lenth and pin diameter. The only difference is the big end. On the 3.0 the big end is narrower.
3.0 is 21.8 mm ? and the 2.7 is 23.2mm ?.

As 959 engine is 2.85 (95x67) twin turbo, haven't you ever thought about building a 2.8SS turbo?

I thought about it but I built a 2.5 turbo for the "914 From Hell" instead.

Would twin plugging be your advice for using intercooler also. I have a 3.0 l also and plan to use 2*GT25. How about 964 RS cams?

K

K:

I'm going with GT20's. How many rpms and what boost target are you shooting for in the end? Aren't the GT25's getting pretty big for a 3.0 (pure question and nothing meant)? Twin plugging would be MORE important without intercooler. Depending on compression, piston shape, bore size and rpm twin plugging could make sense.

Update...
 

The car is running great and feels incredibly quick. So quick, that I fitted a safety devices roll cage for safety!! I also fitted a duck tail and am in the process of removing the rockers. I thought I would enhance the sleeper effect. I am going to have the car on a dyno within 2 weeks and can't wait to see the numbers. When I get the numbers, I will post them here.
Thanks again Henry, for such a fun ride.

Bryan

Henry,

Could you elaborate on the "1 MSD 6Al triggering two Blaster II coils"

Thanks
Scott