Is this TDC?

Touque · 11-03-2002, 07:54 AM

my turn for a question that a few of you may consider 'dumb'! oh well.

My problem from before (912 smoking and spitting oil) is most-likely my #3 cylinder running too rich. Thanks for all your help.

This question involves TDC for my 68 912 - my pulley does not have the 'usual' mark on the outside to show it. The only identifying marks look like this:

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if this is the pulley looking from above and the | are the notches.

and it looks like the other side (180 degrees turned - BDC) looks like this with 2 marks (notches) on the rear edge:

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I'm 'guessing' that the top one is TDC and the bottom is BDC. I have adjusted my valves based on this, but they seem loud.

Do you think I could have adjusted my valves based on the wrong mark and adjusted my timing after putting in a 050 distributor (again based on the wrong mark), and still got the car to run properly (almost perfect...)? Or have I done it correctly...? Would it even run if it was off 180 degrees?

thanks in advance.

Duke · 11-03-2002, 11:41 AM

To find TDC of #1 turn the engine over CCW until the TDC or "OT" mark on the pulley lines up with the vertical mark on the crankcase housing and at the same time observe that the dist. rotor points to a small notch on the edge of the dist. That is cyl #1. Then continue turning the pulley CCW 180 degrees, this will be cyl #2 (the marks on the bottom of the pulley should now be lined up with the vertical mark mentioned above) Continue turning CCW another 180 degrees, this will be cyl#3, another 180 degrees will be cyl#4. Observe the rotor each time you turn the engine 180 deg & it should line up with each spark plug wire leading to that cyl. Hope this helps.

Touque · 11-03-2002, 01:12 PM

I have all that as well in a few books, but I'm really looking to find out if I indeed have TDC or the OT mark identified correctly. I think the distributor rotor can only go in one way as the 'prongs' in the bottom are not centered.

adot · 11-03-2002, 02:34 PM

Follow The DUKE's reply, its right on the MARK.

GoodLuck
Brett

adot · 05:15 AM

Hey Touque

Guess what, just found out that the letters 'OT' are embossed right below the TDC( OT ) mark on the outside pulley. Smart, smart, smart they were at Porsche. If the OT mark was on the inside pulley, you could never be 100% if you have the right mark because you cant see that side to see the OT embossed.

GoodLuck
Brett

Touque · 11-13-2002, 06:16 AM

cool

I know i've heard about the 'OT' letters, but now it makes sense. I'll have to look as soon as I am back home from my trip.

thanks Brett!