Distributor rotor position and notch/distributor orentation timing issues

[ARCSinAK]

I struggled yesterday to verify the rev limiter rotors position at TDC after reinstalling distributor. The position of the distributor effects the its orientation. I marked the distributor previous timing position with a scratch but want to verify the rotor as it seems one tooth either way is close. Is the small dot on the wide rev limiter rotor what should line up with the notch on the distributor? I remember the no rev-limiter rotor being more straight forward in terms of lining up with the notch.





This pulley is from a 74, there was no mark for advance 35 degrees before TDC all the timing threads I have research say there should be. I measured with a metric sowing tape 35 mm and put a notch on the outside of the pulley. ??? I presume the marks to the left are for MFI??

I had a couple dramatic backfires hopefully nothing was damaged in the 76 CIS system that I replaced the original 74 set up with, a smoke test revealed major air leaks I was able to install the 6AL MSD box and Pertronix ignitor as this 911 was running previously with no CDI. Upon 1st start up it ran but was stumbling seems off then I could not determine the timing and thought I was a tooth off. May have been 180 degrees off as the timing light registered no marks. Hard on Kauai as there are no 911 experts. I want to make sure I get the number 1 TDC right before I continue.

And advice would be appreciated.

[john walker's workshop]

Distributor position, rotor/notch, looks about right. Usually the distributor isn't right up against the stud though. To determine #1 TDC, pop off the left upper rocker cover and see if #1 rocker has some clearance. TDC mark could be #1 or #4. What about the massive air leak? Did the airbox split the seam?

[Flat6pac]

You need the crank pin locator at 9:00
The 2 marks in the left on the picture are either Z1 and 5 degrees or 30/35 BTDC
If it’s Z1 you’re distributor is too advanced, if it 30/35 you’re white markis is close to TDC for 2/5 depending as John noted checking the #1 intake rocker for the looseness of the valve adjustment
Like I said in the first sentence, you got to know that the pulley pin locator is at 9:00
Bruce

[ARCSinAK]

Hi John-

Thank for your advice. The original air box had a leak, I had a spare 76 CIS system that came from a good running 2.7. Installed it with all new seals, new injectors. After installing I had the same issues, cold start and cutting out under full throttle I did before. I was so frustrated. It would only start if I bumped the sensor plate, after I manually idled it to temperature it ran pretty smooth and strong on the first couple of drives but then developed the same issue of cutting out under full throttle I had before the CIS change. I attributed that to ignition/lack of CDI since I had changed the entire CIS system. I also changed out the thermo switch and used the 76's 7th injector harness as the 74 had a different connector hoping to cure the cold start issue but no dice. Decided to install the MSD 6AL box to rule out ignition. I installed the MSD and it started but it was not right. It ran but motor seemed out of balance. I noticed the sensor for magnet was loose on the Pertronix, removed distributor to address that issue and that's were things went south with the timing. Had a couple of radical backfires, 44 magnum kind, think I was 180 degrees off once ETC. Now I only get an occasional burp/pop no start. I am aware that bumping the sensor plate to start is not all that wise given the uncontrolled fuel and mixture problems. Hopefully the mufflers in one piece and the 76 air box is still intact. Had to walk away yesterday. Is there any other way to determine TDC on number 1 with out removing the valve cover?


Flat 6-
Crank Pin indicator? Hole in the pulley? The pin that holds the distributor? When I have the distributor adjusted to the original position, aprox center, the rotor dot seems to be off a little in each direction depending on what tooth I'm on. Thats what I found confusing.
These are the only double notches on the pulley, also no Z1 engraving. Does that rule out that the marks on the left could be 30-35 BTDC ? Could the motor have run at all if I had it 35 degrees out? I have timed it before using the marks in the center image and when I rev (advance) the motor the timing light view on the pulley moves to the right of the two center marks. The only other marks on this pulley are singles at apron 90 degrees. I searched a bunch "pulley marking threads" and have yet to see a diagram of a pulley with the marking mine has???

I sure appreciate you patience with my remedial questions.

[eastbay]

Here is a pulley diagram, looks like you have your pulley marked wrong

[ARCSinAK]

Thanks for the diagram. My motor is base US 911. Could it have ran for years if it was timed at 35 before TDC?



Went to Bruce’s book and found a clear image of the rotor position.

[frosty2]

My pulley looked a lot like yours with no visual Z1 marking but someone on the forum
suggested using a mirror to look on the back side of the pulley and bingo there it was.
If it the same pulley as mine it is one of the two marks to the left on your picture as
Bruce mentioned.
Thanks
Mike

[frosty2]

Also I struggle with verifying the position of the rev limiting rotor as well so I keep
A standard non- rev limiting rotor around for when I’m messing with stuff and when
I’m finishing lining things up I pop it off and stick the proper one on.
Makes it easier for a non mechanic like me😁

[Flat6pac]

When you’re setting up static, the crank pulley on Z1 you want the leading edge of the rotor at the mark on the distributor
I’m still concerned with the pin locator locking the pulley to the crank nose.
I’ll look at a couple pulleys and take a picture.
Bruce

[Flat6pac]

These are actual pulleys with markings
Notice rhe 2 holes are vertical with the locator pin at 9:00
Not so on your pulley in picture.
Bruce

[ARCSinAK]

Hi Bruce-

You are correct my pulley has no such no pin locator. Humm

Should I pull there valve cover and check rocker on number 1?

[Flat6pac]

Pull the bolt on the pulley. Sometimes the washer or flange hides the pin. Without the pin, you don’t know where you are in relation to spec
The rocker stays loose for about 3/4 the way around the pulley so you can’t still find Z1 but you can see which rotation you are on, #1 or #4
Bruce

[ARCSinAK]

Ok going there now.
Is a two pin spanner wrench required to secure the pulley in order to loosen the bolt? Torque Spec to re tighten?

[Flat6pac]

Good question. Sometimes the bolt requires heat to break free
Spinner could help...
Bruce

[ARCSinAK]

Bruce was right again!
Located pin, currently I’m 180 out on the rotor when the pin is at 2100 hrs.

Still strange how it was even running if it was timed at 35 as TDC
Can I be confident that when the pin is at 9 o’clock I am at 1 TDC?
Then re set distributor?

Wondering if I should completely remove pulley as in theory it could be flipped end or end with the pin locater hole in the same location, resulting in 180 off as the pulley notches are cut into both sides???

[ARCSinAK]

Shouldn’t the side of the pulley with MFI timing Notch be towards the fan housing?

[Flat6pac]

No you can’t be confident until you pull the top valve cover left side, set pulley to Z1 and check #1 rocker for lash which should rock. If it’s tight, check #4 intake to feel valve lash.
One rocker will be loose and the other will be tight and moving down as you turn the crank.
When you come up to Z1 one rocker will be loose, if it #1, you’re TDC adjust the distributor to the notch with leading edge of rotor to the notch
Note, did you check the pin locator on the crank nose as they do elongate if the pulley isn’t tight.
Bruce

[Trackrash]

If it was me, I would do as Bruce suggests AND make up or obtain one of those devices that replaces the #1 plug which is used to determine the TRUE TDC.

[ARCSinAK]

I'm so grateful for all of the advice. Lucky to have this community.

I pulled valve cover, established TDC on #1.
Got the timing dialed for the first time in a long while.
Took the "Tarpa" out for a test run, she ran better than ever. SOOOO Stoked.
2nd test run dialed in idle, mixture and timing a bit more by ear. Dam near Brazilian Smooth.

Now need to solve the on going do I need a MSD tac adaptor or not mystery. Currently no tac.
I'm running pertronix no points. If I just touch on and off a jumper from the purple and black wire in the original 3 pin harness to the negative side of the blaster coil I get intermittent bumpy tac readings. If I leave it connected nothing. If I connect the wire from the tac to the "Grey" MSD tac output wire nothing. ???????