Thursday, 5 April 2012

Porsche 944 Cam Belt

Sometime after the arrival of the first Porsche 944s, we started to get problems with cam belt alignment, which culminated with a number of belt problems and with several engine blow-ups with pistons hitting the valves. We looked at this in some detail and by this time others were having the same problem, which the Porsche factory was saying was a fault of over tightening of the belt adjuster.
Rob McEwen sent off our findings from our own in-depth investigation to the Porsche technical department at the factory, as we had found a design fault with the pulley adjustor, the thinness of the wall of the offset hole, on the aluminium cylinder head. This acted like a stiletto heal on a soft floor and the adjuster when repeatedly retightened to the factory torque settings, was imbedding itself in to the soft aluminium head and consequently the pulley was going further and further out of alignment.
This only happened to the Porsche 944 cars that the respective Importers had bothered to make the service adjustments on. So in effect the mechanics carrying out the Porsche recommended adjustments on their customers cars were the ones only suffering from this problem. It actually showed up who was and who was not carrying out the regular service as prescribed by Porsche.
Porsche at first refused to except that this was a design fault and we continued to fix all cars with us (with or without the problem) by using extremely thin hardened steel, shimming washer placed between the cylinder head and the belt adjuster pulley.
Bob came up with a new design to permanently fix this problem with a new stud adjuster design with a stepped collar to seat the pulley adjuster. Rob sent this off to the factory as a suggestion permanent fix for the problem that by was now giving Porsche a number of problems worldwide. However, there was still a refusal to accept any suggestions from us.
In the following months Porsche finally came up with a modification by way of a Technical Update, this it turned out was almost identical in design to what had been sent to them!
How much time was lost and how many cars had failed, I do not know. However it was a typical reaction from Porsche, who are so advanced and who think of the smallest detail in every way, that there just can’t possibly be anything that has been overlooked. Their pride will not let them accept a solution from anyone outside of their own organisation.

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