Distributor

[930 porsche]

I have a distributor wondering where the 2 vacum lines go to? 1 has been hooked up to the intake i believe and the second one was open to the air so I decided to put a plug. To make sure of those 2 vacum lines where should they go?

[930 porsche]

What do you think about advancing the timing on the distributor until it starts knocking then back off a little for more performance?

[mark houghton]

Originally Posted by 930 porsche

What do you think about advancing the timing on the distributor until it starts knocking then back off a little for more performance?

I wouldn't do that. You would end up too far advanced when on boost and melt holes in things.
If you want to run more advanced timing and have the assurance that the proper amount of retard is in place when on full boost, do as I and a few others have done with an MSD boost ignition retard.

[930 porsche]

Explain what it is and how it works. Thank you. What about those 2 vacume hose?any idea where they go?

[Speedy Squirrel]

'86 to '88 USA car? They go here:

[cole930]

930,

The 2 ports on the distributer, one is vacuum advance and one is vacuum retard. Do a search for distributors and you will find lots of info.

Don't ever set timing by advancing until it knocks then backing it off. It needs to be timed by the book at 4000 rpm with a timing light.

If your using a MSD 6AL ignition system you can buy a MSD Boost Timing Master this allows you to bump up your initial timing setting for better low end grunt and then when boost starts it allow you to retard timing so many degrees for every PSI of boost which prevents detonation at higher boost level.

Cole

[930 porsche]

I have some picture for you. Just circle the vacum line where ever they go. I have a total of 5. 4 in the back and 1 in the front of the throttle. Here is the VIN #9308800085. The only line hooked up from the top vacum line of the distributor is going to the front throttle bottom vacum line. Is this correct? Also I believe my WUR is hooked up to the back of the throttle in the one that has a T which will be sharing the blow off valve. I plugged 2 small vacum lines which were connected to each other with a silicone hose doing a U so I figure it is the same as plugging them individually right?

[Speedy Squirrel]

For the two lines that go to the tee, one on the left goes to the vacuum control (also called the blowoff valve, it is the big round can mounted between the upper and lower intake, hopefully you still have it). The one on the right goes to the warm up regulator.

The two that are at the top of the throttle body and capped go to the EGR valve on California cars, and are capped on others (EGR valve is often removed on California cars).

The line at the bottom goes to the thermo switch, and from the thermo switch to the distributor outside connection. This is what the thermo switch looks like:



The other line goes from the back of the distributor to the cut-off valve (electrical valve mounted on the upper intake, also often removed). The cutoff valve has a vacuum line that tees into the thermo switch vacuum line, and the other connection goes to the warmup regulator atmospheric vent (the line that connects to the air cleaner (also often removed).

On older cars it is hard to get everything connected back the way it was supposed to be because various components have been removed over the years.

[Speedy Squirrel]

In your case (1978 930 USA car), and considering the items that have been removed, this is what I would suggest:

Connect A to the vacuum control (blow off valve, big round canister connecting upper and lower manifolds)

Connect B to the warmup regulator

Leave C and D plugged

Connect E to port1 on the distributor

Leave port2 on the distributor open to atmosphere (do not plug)

[930 porsche]

I just want to thank all of your input especially Speedy for coming through for me. Understanding the functionality and where they all plug in was one of my goals to accomplish amongst other.

[fredmeister]

NOT TO ADD confusion, but Speedy Squirrel has some sound knowledge of the turbo set up. great write up.
I wanted to ask if the Port 2 on the dizzy is the boost retard port? if leaving it open to atmosphere, aren't you removing the ability to retard timing under boost from the dizzy?
along that line of reasoning, i found that port 2 can be connected to the same line as port 1 described, by installing a small tee and thus you can gain back the retard feature on boost that would go unused by leaving it open to atmosphere.
tell me if you don't agree and please explain.
I am referring to my 79 930 which seems to have the same setup as described here.

Fred

[JFairman]

The correct vacuum line arrangement is in the owners manual (it almost takes a magnifying glass to read the little roman numerals next to the TB vacuum ports and lines, and in '87 the TB insert was printed upside down to add to that confusion) and on the inside of the engine lid, if the complete decal is still there.

Unfortunately alot of what has been posted in this thread is wrong, incomplete, or backwards.
It becomes a waste of time to try and correct it though because there were small differences in different years and what country the car was sold in, and the people posting wrong information think they are right.

[billjam]

This is the diagram for 1986 cars from the Owner's Manual. It may help clarify.

[Speedy Squirrel]

Thanks Billjam, but Porsche930's car is a 1978 USA, which has a completely different throttle body. The early model cars (1976 - 1979 EURO, USA and ROW) have throttle bodies that can be recognized by the two vacuum ports that angle off to the right when viewed standing behind the car. This is clearly seen in the pictures that have been posted.

I used the diagram in the workshop manual for this model year and engine, so I am quite sure the connections I described are correct. I would like to post it here, but I think it is against the rules. If this is incorrect, please let me know. I think it would be helpful for others as well.

I recommended leaving the backside port vented because Porsche930 has lost his cut-off valve. It is connected to the air injection system, so many people discard it, not realizing that, on these early cars, it also connects to the distributor and performs the full boost retard function as well.

If Porsche930 backs off 5 degrees on his static timing, and leaves the boost retard port vented, he should be safe. That is similar to how the EURO cars are set up; they do not even use the boost retard port.

[Speedy Squirrel]

Fredmeister, I agree with your idea, and Porsche930, it is another way to go. Even with the same pressure on the front and the back of the diaphram, there is a retard effect under boost, due to the way the springs inside the capsule bias the two pressures.

[930 porsche]

jim I need you to talk to speedy to come in agreement for the vacum set up. I am confused now. Your disagreement between speedy and fairman is about C, D, E,port1 and port2 connections? A and B you two are in agreement.

[JFairman]

the way i described it in mulitiple emails with you is exactly the same as the 1986 owners manual vacuum line diagram billjam posted above.

compared to an '86 your TB has one extra port next to the vacuum advance port that you said is for operating egr valves.

[930 porsche]

So we agreed:

A goes to BOV
B goes to WUR

Notes: Can A goes to WUR and B to BOV which should not make any diifference since they are sharing the same line as a T? I am asking this question for ease of set up because I am using a high grade vacum line that can be bent to a certain degree only from my BOV.

Our confusion are:
C to Port1?
D plugged?
E to Port2?

Knowing that Port1 is vacum advance, Port2 is boost retard and E vacum retard. With this information we should be able to come up with an answer for all of those connections. I need your help in finishing this vacum project. Thank you.

[JFairman]

port 2 on the distributor is vacuum retard. it pulls back the timing at idle and deceleration to lower certain exhaust emissions.

there is no "boost retard port"
under boost there is no vacuum anywhere, just air pressure and it saturates both vacuum lines so vacuum advance and vacuum retard cancel each other out or they are equalized on both sides of the diaphram in the vacuum pot so it is in the middle position, not advancing or retarding the timing.

so, without any vacuum advance or vacuum retard going on you only have centrifical advance happening and that maxes out around 3000rpms in most distributors.
that said, without total igntion advance (centrifical and vacuum advance together) with boost pressure in the intake system this scenerio is called boost retard.

hope that makes sense to you.

[930 porsche]

Jim Fairman thank you for the education about clearing up the Vac advance and Vac retard. I guest I did not use the right verbage and called it boost retard instead of Vac retard.