[Cloud9...68]

[quote name='sparky' post='46795' date='Feb 2 2008, 07:18 PM']An very experienced mechanic friend suggested the tension should be such that I can twist it through about 90 degrees with my fingers.[/quote]



That's a helpful hint that I hadn't heard before. I'll have to remember that when I do mine.

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[sparky]

When I get the belt re-tensioned with the official tool this week I'll ask them to do a calibraton check on the current tension (done using 90 degree twist technique). Then I'll know whether it's really a good rule of thumb for our balance belts.

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[Cloud9...68]

Thanks. Love your avatar, by the way. Have you done a lot to stiffen the chassis to allow the left front wheel to get airborne like that?

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[RS Barn]

I'm not a fan of the twist 90 degrees test.

But I do have a quick check for balance belt.

If you put your finger under belt at 4 Oclock to waterpump roller and push toward wp roller, it should just about touch with light tension on your finger. You can actually feel when the belt has reached the end of its slack vs belt tension. If it touches easily-too loose. If it gets real taught way before roller too tight

Pete

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[sparky]

I'd go with Pete / RS Barn's tension test rather than my rough 90 degree twister - he's surely done this a lot more than me !



As for flying a wheel in my avatar - actually that photo is a bit of a fudge - the wheel has just been launched by cutting the ripple strip .... but I'll take the credit none the less <img src="/forum/images/smilies/968/cool.gif" class="smilie" alt="" />

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[PorscheDude]

[quote name='sparky' post='46844' date='Feb 4 2008, 03:02 AM']As for flying a wheel in my avatar - actually that photo is a bit of a fudge - the wheel has just been launched by cutting the ripple strip .... but I'll take the credit none the less <img src="/forum/images/smilies/968/cool.gif" class="smilie" alt="" />[/quote]



That is a great shot!

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[Cloud9...68]

[quote name='RS Barn' post='46835' date='Feb 3 2008, 04:40 PM']I'm not a fan of the twist 90 degrees test.

But I do have a quick check for balance belt.

If you put your finger under belt at 4 Oclock to waterpump roller and push toward wp roller, it should just about touch with light tension on your finger. You can actually feel when the belt has reached the end of its slack vs belt tension. If it touches easily-too loose. If it gets real taught way before roller too tight

Pete[/quote]

Thanks pete, that's very helpful. I'll do this when replacing my belts in the next month or so.

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[apex]

fantastic thread. thanks guys - especially pete!

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[schwarz968]

[quote name='sparky' post='46795' date='Feb 2 2008, 08:18 PM']The workshop manual descriptions for removing / replacing the camshaft & balance belts is pretty good. Once you have them removed the water pump is pretty straight forward: just undo all the bolts/nuts around the perimeter and gently prise it off. Clean up / remove the old gasket remnants and fit the new pump. Then follow the manual on how to get the belts properly aligned.



There is one slightly tricky bit - setting the balance belt tension requires a long 27mm spanner and a special Porsche tensioning tool, or at least good experience to know what is right tension. Not that I'm that experienced, but I tensioned it without the tension tool ... at first it was too tight and noisy, so i loosened it a tad and the noise reduced accordingly. An very experienced mechanic friend suggested the tension should be such that I can twist it through about 90 degrees with my fingers. That's where it is now, and it's working/sounding fine, but this week I'll take it to the local Porsche workshop to get it properly tensioned with the proper Porsche tool.[/quote]



I just posted an Ebay listing to sell my tensioner and calibrator if your intrested. Item Number is 290204712294



Schwarz968

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[RS Barn]

Just a weird note.

Using the factory tension tool at .9 , You would be amazed how much tension is required on the A/C Alt belt.

It scares me all the time.

Pete

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[sparky]

eBay offer is good, but starting at US$475 is a bit exe .... must be quite expensive from the factory.



Pete - what about belt tension on non-A/C cars with no compressor and proper Club Sport mounts for alternator?

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[SpeedRacer64]

[quote name='sparky' post='47064' date='Feb 8 2008, 02:07 AM']eBay offer is good, but starting at US$475 is a bit exe .... must be quite expensive from the factory.



Pete - what about belt tension on non-A/C cars with no compressor and proper Club Sport mounts for alternator?[/quote]



I just LoVe that picture...

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[RS Barn]

Sparky,

Belt spec is same for A/C and non A/C

It is still .9 on factory guage. Tight as ____

There isn't any deflection. This is just how Serp belts work-very tight

Pete



Sparky,

We just need an RS Barn windshield banner and move driver to left side to make picture even more awesome.

Pete

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[sparky]

[quote name='RS Barn' post='47101' date='Feb 9 2008, 12:24 PM']We just need an RS Barn windshield banner and move driver to left side to make picture even more awesome.

Pete[/quote]

<img src="/forum/images/smilies/968/rolleyes.gif" class="smilie" alt="" />



... 968's are faster in the southern hemisphere <img src="/forum/images/smilies/968/tongue.gif" class="smilie" alt="" />

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[sparky]

OK my balance belt is now set to specified tension by experienced Porsche mechanic using the Porsche tool. Gotta say it's not that tight at all - quite surprising. The mechanic assures me it's correct.



I checked it using Pete/RS barn's technique (described earlier, just touching the water pump pulley) , and my 90 degree twist technique (also described earlier).



The answer is .... both are right ! In fact I'd say with confidence, using both techniques as a double check is the perfect answer.



Another thing I learnt along the way - the belt whines when it's overtight (which is easy to do)

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[JWahlsten]

Well, I just got done doing the Vario-Cam pads, the cam chain, and timing the cams. I must say the procedures given in this DIY were spot on, and with a few pointers from Max at RSBarn while I was picking up some goodies, the project isn't too bad. The worst part was getting some of the bolts loose and removing the timing belt tensioner.

So, now I have two dial gauges to add to my Porsche maintenance required tool collection ... If anyone needs to do cams and are in the local area, I am will to lend a hand or tools as needed.

What's even better is I did the airbox mod at the same time and the ole butt-o-meter says the car is stronger. Enough of this, I'm going for a drive.

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[sparky]

great to see my work still making the odd '68 get faster.... cheers

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[JWahlsten]

It certainly did, thank you... It was a good write up.

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[Cloud9...68]

One question that doesn't relate to the timing of the cams, but which is an integral part of the head R & R procedure: How did those of you who did this job tighten your cylinder head bolts? I understand the "tightness" of the bolts isn't expressed in term of torque, but in terms of angular displacement. What kind of tool do you use to tighten the bolts?

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[RS Barn]

Snap On sells a wonderfull Torque Angle Guage!!!

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