Ignition Timing and Distributor question

[Boxster Rod]

I have an '88 930 that I'm trying to sort out. First thing is setting the timing. I know it should be at 26 degrees BTDC at 4000 RPM, but how do you determine where 26 degrees is? To clarify, I do have a timing light, and see two marks for timing - one on the fan housing, and on on the pulley - I assume when these line up that this is zero? Is 26 degress (or any other mark) on there? If this is zero, I roughly figured 26 should be about 1.2 inches over. I've looked everywhere and nothing I've seen tells me.

Second thing - the distributor has 2 vacuum ports. I pulled a vacuum on the port on the "right side" (facing engine from back of car) which caused the timing to retard. Pulling a vacuum on the other port seemed to have no effect on the timing. What should these ports do? I assumed pulling a vacuum on the "left" port would cause an advance in timing? But you know what happens when you assume...

Thanks much

-Rod

[e170drvr]

Boxster, My 87 has a small notch in the pulley. hard to see but its there. obviously if your timing light is adjustable simply dial in 26 degrees. The vacuum pot as I understand it will give you a little advance when the car is cold, the pot facing the engine is retard, and will give you around 10 degrees or so retard on boost. If you can't get the advance side to do anything, try and put a few drops of oil under the rotor in the felt pad. the mechanism may be gummed up.

[Boxster Rod]

Well, my friend's dial back to zero light was DOA,so I had to fish out my old standard timing light. I'd seen pics of other 911 pulleys that had additional marks w/ numbers for timing, just wanted to make sure I wasn't missing something. I gess it's time to fix my friend's timing light or find another.

As far as the vacuum unit, does anyone know if this uses a common internal diaphram for advance/retard?


Thanks again

-Rod

[fredmeister]

I am not sure the function of the ports on my 79 930 distributor as well.
The port on the "right side" (facing engine from back of car) on my distributor is not connected to a hose, ie it is open to atmosphere.
I pulled a vacuum on the can on the other port facing away from the engine and it did nothing.
This port has a vacuum line from the throttle body atached to it, but I assumed this was the vacuum advance connection, and the other port that has no hose is the boost retard, am I wrong?

thanks

[RarlyL8]

Fred, your engine is a 930/63 California 930?
For that engine there is an extra vac pot that retards at idle for smog purposes. The other vac pot works by preventing further advance in the absense of vacuum. In other words it cancels out the vac advance once the transition to boost occurs.
There was a thread a few weeks ago on this subject where out takes of the factory manual were included. The California 930 is rather complex with the CIS add-ons for smog control.

[fredmeister]

Not sure what components/engine type I have, passed thru too many hands to know for sure.
I think we may be miscommunicating, there is actually only one vacuum canister on my distributor, it is just that it has a port on each side of the canister split line. One faces the engine which is open to atmosphere, and the other port/nipple is on the side away from the engine, and this one has a line from the throttle body connected to it. This seems to me that each nipple is on either side of the rubber diaphram that should be inside the can, and they probably counteract each other.
Now I am not saying this is stock because of the fact that the car has seen 3 owners and all the exhaust/smog equipment has been removed. It still had the US exhaust but the thermal reactors were replaced with a cast 3 pipe collector. I am not sure really what should be on the car and this is what worries me with regards to the ignition timing.
I will try to post pictures of my set-up once I have time to take some.
Do you have any pix of the non-california distributor as Boxster Rod described?
Also, how critical is it to have the boost retard still connected? I am assuming that this function has been removed on my distributor via the open port/nipple.
If this is disconnected what would be the proper timing to run as far as max advance under 0.8-1.0 bar boost?
What would be the initial timing roughly at idle to get to this setting? As this is how I would set up the timing at idle and then run it up to 4000rpm and check max advance. The owners manual I believe states that these should be set at 5 degrees ATDC at 950rpm.

Thanks for the info,
Fred

[NathanUK]

Is it like mine? Both ports on mine are connected, I took this pic while the car is in pieces for upgrades

[fredmeister]

Yes, mine looks just like this picture. Except the only port that has a hose connection is the outside one away from the engine block. The other one is left open to atmosphere.
I pulled vacuum on the outer one that has the hose connection, and saw no change in timing. Is this possibly the boost retard side? I did not have a way of applying pressure to it to see if it retarded timing.
I checked the centrifical advance and they work. I get about 20 degrees of advance at the crank at 4000rpm . Is this a little on the low side?

fred

[fredmeister]

Bump

[RarlyL8]

Typical timing is set at 26* @4000rpm.