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Timing question

 
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rcarson25  



Joined: 14 Dec 2020
Posts: 7
Location: Middle TN

PostPosted: Wed Dec 23, 2020 12:50 am    Post subject: Timing question Reply with quote

I just did a timing belt and water pump on my newly acquired 1981 924 turbo. I have attempted to align the timing marks, but cannot seem to get the cam gear timing mark perfect. I have set #1 to TDC but the cam gear mark seems to be about 1/2 tooth off. Any suggestions or is this common. Thanks in advance.
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Carrera RSR  



Joined: 08 Jan 2010
Posts: 2104
Location: Somerset, UK

PostPosted: Wed Dec 23, 2020 1:00 am    Post subject: Reply with quote

Probably due to head skimming. Better to be 1/2 tooth advanced than retarded. Only way to be cock on is a vernier pulley or thicker head gasket. Although the marks are a guide and not an absolute.
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1980 931 - forged pistons, Piper cam, K27/26 3257 6.10 hybrid turbo, 951 FMIC, custom intake, Mittelmotor dizzy & cam pulley, H&S exhaust, GAZ Gold, Fuch'ed, Quaife
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rcarson25  



Joined: 14 Dec 2020
Posts: 7
Location: Middle TN

PostPosted: Wed Dec 23, 2020 1:38 am    Post subject: Reply with quote

Awesome, exactly what I wanted to hear advance is where I set it assuming that would be better as well.

Last edited by rcarson25 on Sun Dec 27, 2020 12:02 am; edited 1 time in total
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morghen  



Joined: 21 Jan 2005
Posts: 8274
Location: Romania

PostPosted: Wed Dec 23, 2020 5:51 am    Post subject: Reply with quote

the crank pulley has a rotational tolerance, loosen the 6 bolts holding it and find its middle position, if you took it off and put it back in a hurry you may have not noticed that.
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peterld  



Joined: 10 Dec 2006
Posts: 808
Location: Noosa Heads QLD Australia

PostPosted: Wed Dec 23, 2020 11:39 pm    Post subject: Reply with quote

+1, plus the locating pin (Porsche calls it a tensioning sleeve) which locates the toothed belt pulley, can bend (particularly when using an impact tool to remove the bolt) throwing out the timing by several degrees.
Using proper engineering dowel pins (spring steel roll pins) is the answer.
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