it looks to me from the pic that the belt just isn't seated down into the teeth. it matches up great for a while, then it pulls away, but it looks like it's long before it should be forcing itself up and out of the teeth

I'd definitely not use that belt. I've never seen a toothed belt that didn't fit out of the box. That goes for both automotive and on machinery where they are used for high torque applications. Sometime you have to work them in place if the fit is really good. But if your pic conveys it correctly, it doesn't look as thought that belt has a chance of having the right pitch. I'd take it back to the supplier to have them compare it to another belt. Or even better, call Gates. Their quality guys will want to see it so they can figure out what went wrong in manufacturing. My guess is either they had a bad run of belts with the pitch set incorrectly (highly unlikely), or they were marked wrong. No way the belt should be that far off.

maybe i'm just not seeing what you are. it doesn't look to me to be off, and certainly not far. the belt has no tension on it. i'd like to see it with some tension on it. i have a feeling it would fall into place.

i could be wrong though. hard to tell from the pic

I'd call them about this

That belt has some tension on it. Both do, I wrapped both around the cam gear and lightly pinched it with vice grips to illustrate how the teeth spacing is too narrow to fit in the gear.

There's no way it will work. It had me scratching my head too when I tried to put it on the car. Since I had 3 other used cam belts, I did a comparison to the others and it's definitely not right. The length is right, but the teeth are out of whack.

Cam belts are cheap, if it was a balance belt, I'd call the supplier.

bought a dealer / Porsche belt a few years ago, when I got the substantial & official looking box, the belt in there simply 'felt' better than the after market belt (sorry, dont recall who's) I had gotten first and still had in hand. Seemed 'stiffer' , maybe heavier(?) than the aftermarket

I went with the factory belt based on feel and paranoia.

Now time to fresh up the belt (6/14) I ordered another Porsche belt, again just over $100, (a wee cheaper than last go , from another online OEM vendor). The box was quite different, very plain cardboard. The belt inside was marked PORSCHE and ISORAN DAYCO, Made in Italy, along with some other #s (see pix). Cant say as the "feel" that was so convincing last time, so no opinion.

Another difference notable from some pix on this thread is the new Porsche / Dayco belt (also the belt I removed, the known old-school factory) has a small groove at the crown of the teeth.

I imagine the groove is either a flex enhancer, or more likely a noise abatement design.

http://forums.pelicanparts.com/uploa...1402637598.jpg

^^
Thanks. Nice and clear picture.
It is interesting about the groove at the crown of the belt.

J_AZ

more than likely that groove allows the teeth get more traction.

Interesting - would be worth while to get a tooth count on this relative to the good belt. I might estimate this one is 2-3 teeth fewer.

I have a Contitech belt on my car... now you guys have me worried...

Contitech does fine belts. They have a 12mos warranty as well; it's the most popular belt for service on VW/Audi as OEM equivalent and there are millions of those cars out there.

Don't loose any sleep about having Contitech belt on you car I had them for the last 30 years and not once did I had to sign any release lol to both mechanics which work on my car either the 944 or 968 and not once did any of those belts fail.I once install a Dayco on my 944 and two days later I threw it in the garbage because of issues with it.:D

I have my doubts about "traction" fwiw.

If you think about how a drive belt functions - pulling the gear along via contact between the SIDE of the belt tooth to the SIDE of the gear, (and recall chain/belt wear never at the nadirs or peaks, but on tooth sides), then the peak of the tooth transfers only a tiny tiny fraction of the force.

nope , I bet some bright young intern discovered that the noise contribution of the millions of little 'pops' of air, forced out when the belt nub slaps into the pulley groove could be mitigated providing an escape path, and the least detrimental place to locate the groove ( missing material, after all) was at the tooth peak which does little work to begin with.

The added flexibility of the belt due to tiny grooves at the top of the stiffest part of the belt ( ie the tooth, as opposed to the valley ) is probably negligible.

Now back to the counting angels dancing on pinheads.

every single belt failure i have seen or heard of on the 968 has been a contitech. i know of no failures reported with gates. gates and dayco were the original designers of the system for the 944 and the 968.

no mechanic i know will use contitech, at least not without voiding their warranty. they all refuse, with many referring to them as "rubber bands".

grooves provide traction. in this case they may well allow the belt tooth to compress a bit more under tension, spread out, and provide more contact on the gear. this may not have much of an effect when the belt is new, but as it ages and hardens, it may well provide better contact.

I put pixs above in thread, but I was feeling generous and sprung the couple extra $10s for a factory Porsche cam belt for my 3L.

I received a factory boxed belt inked up with 'Porsche' and 'Dayco Isoran', FWIW.

Damn did veedub switch all spares to 'lowest bidder'?

I put a Contitech belt on the less critical balance shafts, as it was cheap nuf and local.

Don't forget to roll the engine back 10 degrees before TDC to make the cam belt tension measurement ! I was missing a page of my old print from clarks garage and almost missed that yikes



Is it just me or is the balance belt annoyingly loose on the long run? I know the belt is just driving two freely turning shafts, but I cant see how that long belt run does not slap at the water pump pulley . PS I tensioned belt with a 9201

[QUOTE=flash968;8115864]every single belt failure i have seen or heard of on the 968 has been a contitech. i know of no failures reported with gates. gates and dayco were the original designers of the system for the 944 and the 968.

YES YES YES,more belt failure with Contitech.We have heard that one before but I,m sure your taking into account number of Contitech belts versus Gates or Dayco install on 924/944/968 in your research.:D

it's not research. it's just from watching and reading for the last 11 years. many versus zero. i'll go with zero, and let the others who want to run an unnecessary risk pay the $5k for the crashed valves when their contitech fails. just common sense.

For what it's worth
 

I have owned my car since new and it came from Porsche with a Uniroyal timing belt. Uniroyal was bought out by Gates. I have my old timing belts hanging in the garage and the OEM Uniroyal and the 2nd belt which was a Gates look identical in design and markings down to the marking fonts.

From the Dayco web site:

Automotive Click the training tab and enjoy some marketing videos including one on the "W profile belt" about the groove on the tooth noted by 'gtgt_bangbang' (I know the video is about serpentine belts not cog/timing belts). The "W" is for misaligned or worn pulleys on their serpentine belts, I don't know about the W-profile on the teeth of a timing belt.

And as to belt construction material changes through the years (and our cars are from the 1980's) I gather that the original belts were neoprene and the newer belts are EPDM or HSN (can we assume this is true of timing belts?):

"Until the late 1990s and early 2000s, neoprene, the original rubber compound developed into serpentine belts, was the primary material in all belts, both original equipment and aftermarket products. While neoprene was, and still is, a good material for misalignment chirp noise, its flex fatigue characteristics are marginal, especially in hot and cold conditions that roll around yearly. In early 2000, due to advancements in belt technology to achieve better performance under those extreme winter and summer temperature conditions, and to get more mileage out of the belt, EPDM became the material of choice for all major belt suppliers." (from Dayco's "Why Belt Dressing Is Not A Solution . .)

For my car: 95107. From the Gates web site: T107 is "HCR (Hi Temp Neoprene)" where their blue belt T107RB is "HSN (Highly Saturated Nitrile)". I can't find what material the Dayco's are made of.

not sure what they were made of, but porsche originally supplied gates and dayco for this system. then they switched to contitech. after a couple of years with multiple failure reports of the contitech, they switched back to gates and dayco.

the issue with contitech is indeed fatigue due to heating and cooling. they just don't hold up as long, and begin to stretch. many people don't realize this though, as they fail to retension their belts every year, as the owner's manual tells them they should (the 968 only requires this on the balance belt due to having a hydraulic tensioner on the timing belt). so, they wait until the belt change, and figure that if they didn't snap, they must have been fine. dangerous assumption. had they retensioned the belt(s) on schedule, they would generally find that the contitech required it more than the gates.

What it boils down to is, any idiot that owns a 944/951/968 should know there is a heavy premium on camshaft belt failure, should it occur. I have a free belt, a Gates belt, pictures are in this thread, take me up on the offer, please. I want to know how your car fares with that belt. I'll stick with Contitech. A used Contitech at that, over Gates.