Porsche Enthusiasts Club Forum

Could someone please tell me what reading I should use for a used cam belt on an 85.5 2.5 lux? The Porsche manual says 2.7 +/-0.3 on the Porsche tool but what does this equate to in kg or lbs?

Thanks

used cam belt are you sure about that...

you must have a very good reason to use a "used" one whatever you do make sure the rotation is the same direction as it came off.

engine suicide comes to mind

If its been on less than a year i'd say it's fair game, if not "best" practice.

Any more than that just change it.

Thanks for your concern but I changed the front engine seals 1 year ago when I bought the car and changed the belt at the same time. I'm just rechecking the tension but it's at 40 lbs which appears to be the internet agreed value for a new belt (about 2.5k miles ago). I'm not a great fan of taking suggestions for the correct value from random locations on the net and I can't find anything about a used belt (although Porsche themselves do quote a value for their special tool) so I'm looking for some guidance from a trusted source. Hence the question. I personally think there is a great deal of paranoia about the cam belt (which may come back and bite me), but I'd like to get it in the right ball park if possible.

Any information based on actual experience would be appreciated.

Thanks

Matt

Hi

The problem with using a USED belt , is not the time its been on , its the TENSIONING TWICE !

I would NEVER fit a belt again once tensioned, even if it has only been on ONE DAY... and thats if the engine had NOT been run... after a year..no way...

Is it really worth risking your engine for the cost of a new belt ?

All the best Brett

I assume this is tensioning the belt that is on the car already, not removing & replacing? For the others they are meant to be checked & if necessary retensioned every 12 months or 12K miles.
Just found it on the Pelican site:-
Timing = 40 (New belt)35 (used)
Balance = 28

http://forums.pelicanparts.com/porsche- ... -belt.html

Perfect, that's exactly what I was looking for, thank you.

You are also correct that I'm not refitting the belt but checking the tension of a belt already on the engine. However, as the general consensus seems to be that a new belt is required I've ordered one from my local OPC and will fit it based on the new reading and then check after 12 months. Thanks for all the feedback which is much appreciated.

I have the Kricket tool, however to tension the cambelt i found it easier to do by feel, the metal guide rail is your friend there, according to a reliable source, when pressing on the back of the belt near the cam puller you should not be able to get the belt to touch the guide rail, when pushing it from behind the bottom of the guide rail, you should be able to get it to touch the rail with only a little force, maybe i'm just slow but i couldn't find a decent place to grab a tension reading from on the cambelt with the tool

When I fitted the belt I just used the 90 degree twist method halfway along the run from cam to crank but with the idler removed. When I checked the tension with the Krikit in the same place it was exactly 40lbs which appears to be spot on. However, it appears that Porsche predicts some stretch in the belt over the first 1500 miles or so which is where the used belt tension comes in. I was quite surprised by the special tool readings recommended in the Porsche data which allows for something like a spread from 2.4 to 4.3 (there are no units defined). I.e. the allowed upper tension is almost double the allowed lower tension limit. Admittedly this is only up to 3000km at which point the belt should be checked and the allowed tension is amended to between 2.4 and 3.0. I've owned and serviced several Ducati bikes which have a rev limit double that of a 944 and the belts are routed around much smaller radii. Both of which put much higher stress on the belt. These days they recommend setting the tension via a frequency analyser to 3KHz when you pluck the belt at the mid point.

I suspect that the belts used these days are much stronger and more consistent than those used when these cars were new. This is certainly the considered opinion in the Ducati world.

Thanks again for everyone's input and help.

If the belt is already on the car and has not been removed then why change it?
Just recheck the tension of the existing belt.

That's what I'd do, the belt is good for 3-4 years or 45K miles. It isn't just the belt it is all the idlers & tensioners as well. The only time I would change a fitted belt was if it got contaminated, oil & coolant being the main ones.