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Posted

Quick visit to Porsche main dealer today in Toulouse, presently surprised by super cool spares department!

Genuine cam chain idler arm axle for less than the net!!

84 euro all in for two axles, i guess there's a lesson to be learnt there!! ( not dissing our friendly parts providers on here ! )

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  • Like 1
  • 2 weeks later...
Posted

84 quid including postage from a very efficient gentleman in Cornwall!

Sometimes an ebay gamble pays off....certainly better than the 600-700 for a new one. It arrived in a couple of days and freshly cleaned too!

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Happy with that!

Spot the difference.....

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one vandalised 

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one nice and pretty

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Then onwards......

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Going around in circles here!!

Mask up, clean with MEK and seal the back of the chain box with our old friend JB.

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Remove seriously obstinate dowel pin

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Grrr, drop a few f bombs, then succeed and smash it back together. 

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next step, pick up the new idler axles from Porsche and fit the new idler sprockets and on to cam timing!

 

  • Like 2
Posted

So when i went to change the idler sprockets i found the shafts worn as well as the sprockets.

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And the arms were dirty.........omg

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So, super easy, remove circlip, and gently tap out the shaft to remove sprocket. Then off they go for cleaning.

Sweet

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Then , new shafts, circlips and sprockets, important to maintain the orientation of the shaft so the oil catch points up when installed.

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Install..

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  • Like 1
Posted

Right now...........Camshaft timing    🤯

So i have dougherty 964 cams, has anyone here had much experience setting them?

What will be the difference between the settings?

I see three options really  0.9-1.1---or---1.26---or---1.4-1.7

I will be running the 3.1 CIS fuel system with SSI's

Any experience here will be happily received

 

Porsche Manual Pre 1980  8.5 : 1 compression

Screenshot2024-02-17at13_29_46.png.542c7c6ac6a2a8b5214f2f6814e6b981.png

Porsche Manual Post 1980 9.3 : 1 compression

Screenshot2024-02-17at13_30_20.png.2de67701a2d8a34a924c0cdda164e3a3.png

Porsche 3.1 document, origin unknown 9.8 : 1 compression

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The same in German

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Dougherty Website info

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Posted

As a single data point ………. I spent far too long trying to work out ‘the’ recommended timing for my 964 cams.  In the end I opted for 1.4 (1.26 being standard 964) - I was after mid-range torque rather than out and out top end power.

[SC based, balanced 3.2 SS, std valves & springs, CRF CDI+ box (locked off dissie mechanical advance) with Jonny’s ignition curve, CIS & SSIs]
 

It seems to go well, but I’ve never put it on a Dyno, nor have any back to back comparisons, so who knows.

  • Like 1
Posted
1 hour ago, PeterK said:

As a single data point ………. I spent far too long trying to work out ‘the’ recommended timing for my 964 cams.  In the end I opted for 1.4 (1.26 being standard 964) - I was after mid-range torque rather than out and out top end power.

[SC based, balanced 3.2 SS, std valves & springs, CRF CDI+ box (locked off dissie mechanical advance) with Jonny’s ignition curve, CIS & SSIs]
 

It seems to go well, but I’ve never put it on a Dyno, nor have any back to back comparisons, so who knows.

Thanks Peter

Out of interest, have you any idea which way will the power characteristics change between 0.9 and 1.7

Posted

Ok now this is starting to hurt my brain 🧠 

#1 Intake

Starts to open 27° before TDC 

Closed at 253 after TDC 

Max displacement 11.43mm

#4 Intake

Starts to open 36° before TDC 

Closed at 258° after TDC 

Max displacement 11.53mm

 

This is with both banks set around 1.4mm @ TDC. 

 

Why is there such a difference??

Is this normal and not particularly critical??

Beginning to think there's a quality issue with these cams.....but they're a fresh regrind and gave never been run.

The supplier has a good reputation so I'm scratching my head.

Also I'm surprised the vernier adjustments are not very sensitive,  one hole difference on the cam sprocket is 0.1mm on the left bank and closer to 0.2mm on the right bank.

Thinking maybe I have to replace the inner sprocket and pin as well........grrrrrr

 

Posted

Sorry, I just read lots, decided that my increased capacity would give me some extra low down grunt & so I didn’t push the low down torque potential of the camshafts.  I think the technical view is that I researched a lot, then just guessed.

  • Haha 1
Posted

So, not to happy with worn rear sprockets and sloppy locking pins its new parts time!

again.....

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Beautiful!

Reassemble and check end float and alignment again. Right bank was bang on but i had to take a shim out of the left bank and try again!

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Now back to cam timing....

  • Like 2
Posted

Cam timing again........searching the net......soooooo much rubbish about 

So i did a rough set ( one dot ) and got within one hole of the right place!! ( i think )

I'm getting roughly 0.2mm-0.28mm difference of lift between the two positions.

I used a DTI in the spark plug hole directly on the piston and i created a degree wheel to put on the crank pull form here https://www.blocklayer.com/degree-wheel

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I marked the first and second attempts with a paint marker on the sprocket so as not to get lost and confused!

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Then measured and got this.....

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So now i'm set at 1.52 to 1.58......think i'm going to send an email to DRC who ground the cam and ask what they normally recommend setting to!

This week i got a spot in a body shop for the chassis......entry in 6 months then 6 months to a year to finish.......i have time !!

  • Like 1

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