Duck

Well the engine is back from being rebuilt. I have most everything back together and was going to put on the new distributor caps on and noticed the rotors did not line up with TDC. Being my usual self, I removed the distributor to line it up exactly. Well I noticed that there is a chip in distributor gear in the engine (it was also replaced for the same issue during rebuild). So I am not sure if it chipped again when replacing the distributor. I would hope this is not an issue since it had that before as well.

My question is that no matter what I do, the rotor will not line up correctly. It is either before the notch or after the notch. In theory, should I be able to get it directly on the notch? I know timing is controlled by the DME so from reading other threads, may not be an issue. I just tend to like everything lined exactly.

Thanks.

crg53

I may be wrong, but as far as I remember, the line up mark is not near the screw holes. Are you sure you are on the TDC for the compression stroke??? There are 2 TDC"s one for compression and one for exhaust.

Duck

Yes, definitely at TDC. The mark for TDC on the distributor is just past one of the screws. I thought maybe the nick was my issue, so I turned the engine just a little and marked the amount needed to move the rotor to end up on the TDC mark. I removed the distributor and tried several times with no luck. Either I was before the mark like before or with a slight movement of the distributor, I would end up past the mark. I reinstalled the distributor to the original position and rotated engine twice to get back to TDC on the pulley to verify I was no better than before.

Does anyone know how much rotor travel there is with moving the distributor one gear? It appears to be a little over 1/2 inch travel with each groove of the distributor gear. Based on what I have tried, I do not think I will get it to line up exactly like before. Hopefully it is close enough to not be an issue.

Should have everything back together to install during Christmas break.

newsboy

The gears that drive the distributor are helical cut. If you start out with the rotor pointing to the distributor
nub, and then seat the distributor, it will rotate clockwise, slightly past the mark, which is O.K.

Duck

Based on the first pic of the rotor, I can get it like that or the next groove takes it to the complete other side of the mark. Since the rotor has a mechanical movement clockwise, what is best - before mark (like pic) or after the mark? Whatever I do, it will not line up with mark.

-nick

If you're confident in the crank tdc mark, then I would dig in and check your cam timing. Something doesn't seem right. Mine lines up bang-on. I take it that both dizzy rotors are off by the same amount? i.e., the dizzy belt didn't slip or break?

Duck

They checked the belt and it looked fine. I would hate to have to get all into the timing since they just rebuilt the engine by a reputable shop. Unfortunately the shop is 2 hrs away.

I am just not as confident at looking at the timing. I will verify TDC at least.

C4inLA

So, are you saying okay to be slightly forward of marks? I started just bit left of dist TDC marks and rotors rotated inline with marks on distributor housings....

RicardoD

Yeah, I've always read to have the marks lined up when installed. What that means is you clock it back a bit prior to install so when you fully seat the distributor and it rotates a bit the marks exactly line up.

Robbrizzle

The TDC mark you want on the pulley is Z1, you want the rota arms to line up with the protrusions on the out side of the distributor, roughly 12 o clock and 2 o'clock or just a tad more clockwise in your image, good luck.

-nick

Duck- You definitely need to call up the shop.

The dizzy runs off of the left cam. I absolutely would not run it if you see a chip on the cam gear. You said that you had the chipped gear repaired in the past? That would require replacing the left cam, something your wallet would certainly remember! However, that wouldn't effect being able to line up the rotors.

Do you remember how far off the rotor was from the pointer before you pulled it out to line it up? As much as 60 degrees? Possible that they used the wrong crank notch as tdc. Without a doubt, don't run it!

Duck

Thanks for all the input. I really need help to figure this out.

Couple points to make sure it is clear the situation (sorry so long):

* Engine just had top and bottom rebuild by a reputable shop. They are definitely not new to Porsche engines.

* Engine has not been installed yet (currently in the process of bolting everything back together)

* Distributor drive 930.102.112.00 (which looks like is on the crankshaft - not camshaft) was replaced as it had a nick. It appears new one now has one. Will call the shop tomorrow. The nick is not deep (probably not even a mm) so not sure how it would affect the distributor. Maybe someone has had this issue as well?

* Somewhat checked TDC - rotated engine to Z1 while observing a screwdriver stuck in cylinder 1. It definitely peaked close to Z1. I guess in theory it could be 360 degrees off, but the distributor rotors would have been way off if the shop was no where close on the distributor installation.

* I tried several spots when installing the distributor (took it out originally to see if I could line it up better). I tried before the mark and watched how much the rotor rotated during install. Backed it up to where it should have lined up perfectly, but distributor would not install. It appeared I was not a groove. So backed it up further to catch the next groove and the rotor rotated and stopped before the mark. I tried several times with no way getting it stop on the mark.

Questions:

* Since they installed a new distributor drive gear on the crankshaft, could it be slightly rotated and that is why the rotors will not line up on the marks?

* Does anybody know the rotation amount of one groove on the distributor gear? I am guessing there are about 12 grooves on the distributor gear, so each groove would in theory move the rotor 1/12 the way round the outer part of the distributor.

* So if the first question is that the drive on the crankshaft is slightly off, what can be done? I doubt they would tear down the engine again to adjust that only. Based on the below thread, the OP's car drove fine.

https://rennlist.com/forums/964-foru...one-tooth.html

* Has anyone seen a nick in their drive gear on the crankshaft? I am guessing it was done during distributor install. Trying to determine if it is really a large concern.

* Lastly, if I cannot get it to line up perfectly (per the shop, it does not need to), what is better - before the mark or after the mark? I am thinking before as the mechanical movement moves it to almost the mark. After the mark, the mechanical movement would move is very close to the next cylinder.

Again, thank you so much for all the input and sorry for the length of the post. It has been almost a year since I drove it last and really was hoping to have it back on the road by Christmas.

fasterlaster

I know it was mentioned before, but do yourself a favor and triple check TDC of the compression stroke. Ensure that both valves are in the closed position as well as being on Z1. Remember that Z1 marks TDC of the piston, but there is a compression stroke of Z1 and the TDC after the compression stroke where all burnt fuels are pushed out.

Duck

Thanks. Will pull off the top valve cover tomorrow and verify this.

Duck

I could not wait - ran out and pulled off the valve cover. Yes, it was at TDC so do not think I can get the rotors to line up at the middle of the marks without drastic measures.