Removing and Replacing Distributor

[Mike80911]

I recently checked the timing on my 1989 930. The timing was about 4 degrees off but the distributor is at the end of the slot so I could not adjust it anymore. I am guessing that the PO had it out and did not line ti up properly when reinstalling. My question is how to tell if the number one cylinder is at TDC on the compression stroke? I have done many American cars but never a 911 and I either put my finger over the cylinder or I also have a TDC tool but I can not do either with the 930. So how do i determine TDC?
Thanks

[Mike80911]

Update on my progress. I turn the motor over to align what I believe to be the TDC mark on the crank, there are 2 marks someone painted one white and one yellow I think I used the right mark. When I remove the cap and align the rotor with the mark on the distributor the distributor slot is all the way at the end of it's travel. I would imagine it should at least be in the center of the movement slot when at TDC. Any input would be appreciated. Thanks
Some Pictures

[Alan L]

it is the 2nd (latter) mark you want for the Z1. The first mark is your deg advance (timing at 4000 rpm mark) - assuming you are rotating clockwise. If you do that you will see the rotor go anti clockwise. There is a mark on the dizzy body - you can see the notch in your pic. That is your #1 TDC firing mark. When the rotor points at that notch you have the mark. You shpuld be on your Z1 pulley mark then. The notch is not a timing mark - just an indicator. It looks like your rotor is pointing at the notch?
Most dizzys are near the end of the slot travel. But if you are fully done and the timing is out, you may be one tooth off for the dizzy. Once you get your Z1 mark and #1 firing right, you could pull the dizzy and try moving 1 tooth. My dizzy sits about 25% short of fully rotated anti clockwise .
You will need to reset timing of course.
Take note when you pull the dizzy, which way the rotor turns. It is a helical drive. But then I would set the dizzy about 75% anti clockwise in the slot, and adjust the rotor setting as you drop it in to see if you can get the rotor to line up close to your notch on the body.
Alan

[Mike80911]

Thanks for the reply. So you are saying that the first notch on the pully spinning the motor clockwise is the one I should use? The one marked in yellow would be the Z1 mark I need to use to set TDC? If you look at the picture you can see the yellow to the right of the white. The dizzy lines up with the notch but with the crank mark at the white marking.

[Alan L]

Your white mark looks to be the TDC. The yellow is to the right of that? In which case yellow is your advance timing mark (4000 rpm). The white is TDC. The rotor is pointing to the dizzy notch - so you are currently at TDC #1 firing.
You could try shifting the dizzy a notch if you are at full adjust and timing is out. You know where you need to land up now.
My TDC (Z1) mark is my timing mark at idle -= 0 deg. Different motors/dizzys are a bit different - vacuum off/on etc. The 4000 rpm is the mech adv timing and is basically preset in the dizzy. When I set my idle mark, the other is also set.
Regards
Alan

[Mike80911]

Thank you for the reply. I am going to move the dizzy a tooth or so and see how that works out.

[Alan L]

Yes - clockwise - 1 tooth, if too advanced and fully rotated on the slot. Then you will rotate the dizzy same way - to follow the rotor. So the rotor should set 1 tooth to the left of the notch. Not sure how many teeth on the drive gear - maybe 12? In which case will be 30 deg further around.
It may work. You should have some spare adjustment if all is correct.
Alan

[Alan L]

Looking at your pic again, if I am seeing it right - you are hard on the end of the slot, but if you are too advanced you should be rotating the dizzy counter clockwise to retard the timing. You have room to move that way. That would put you around where mine is on the slot. You may not be a tooth out - just adjusting the wrong way?
Alan

[Mike80911]

I believe the timing was about 30 degrees BTDC at 400 RPMs . I just texted a friend who was with me when we checked to see if he remembers the exact number.

[Alan L]

Depends on your motor and dizzy - but that is correct for some, and 26 deg for other set ups.
If that yellow mark is 30mm round (circumference) from your TDC mark, that will be correct. That will be where you should be at with 4000 rpm providing your idle setting is correct also. Usually zero deg - but some are with vac on and some without.
Alan

[Mike80911]

Thank you for all of the advice

[Alan L]

Sometimes people like to set the idle timing a few degrees advanced - like 5 deg. This provides a bit better low throttle/pre boost response. But this will have the effect of pushing your advance timing 5 deg further also.
The idle spec is usually 0 +/- 2 deg. I don't have access to that data right now for specific models.
Alan

[flightlead404]

Originally Posted by Mike80911

I recently checked the timing on my 1989 930. The timing was about 4 degrees off but the distributor is at the end of the slot so I could not adjust it anymore. I am guessing that the PO had it out and did not line ti up properly when reinstalling. My question is how to tell if the number one cylinder is at TDC on the compression stroke? I have done many American cars but never a 911 and I either put my finger over the cylinder or I also have a TDC tool but I can not do either with the 930. So how do i determine TDC?
Thanks

Just stick a short piece of dowel down inside the cylinder, or a 1/4" extend-o-johnny and watch if its rising or falling as you turn the engine carefully (by hand obviously)

[Mike80911]

Thank you

[Mike80911]

Next update. I moved the distributor what I believe to be one tooth. It seems to move the rotor quite a bit almost to the end of travel for the slot in the opposite direction. I have not had a chance to check the timing yet have to get someone to hold it at 4000 for me. Does that seem correct that one tooth should move the rotor that much?
Thanks

[Alan L]

If you counted the teeth on the dizzy shaft you could calculate it. If 10 teeth then 36 deg. Yes - a lot of movement.
If you were fully at the end of slot as in pic,....and advanced in timing, then retarding it will give you some spare slot.
I suspect you were probably on the correct tooth originally.
You should be able to check the idle timing. If that is correct, the advanced should be right also - but will pay to check.
Alan

[Mike80911]

Thanks Alan and if I were you I would go with the Fuchs painted white with a anodized lip I had them on my white 930 and they looked awesome. I'll post a pic on your thread