Timing Belt Tension Poll....

[stitch2k1]

You're missing an option for the poll: auto-set via the spring loaded tensioner (that's what I've been using since 2008 and over 120,000 miles of daily driving)

Seems to be work fine. I do take the tensioner off, clean and lubricate it before installing

I disagree with this, cause after 30yrs of age I do not think you should trust it to be accurate. I've since then seen issues with super weak ones being nowhere near spec.
Maybe ok on a personal car, but I always use a tool on a customer's car, and I keep records of everything being in spec.

If you fit a new water pump every 2nd belt change too, I'm glad I'm not a customer.

That's pretty much the interval that every 944 shop works by. I follow it since it's a hell of a lot cheaper to pay for a water pump every about 8 to 10 years than it is to pay me to replace everything cause it leaked.
I also charge MUCH less than a traditional shop. So I'm still cheaper than just a timing belt replacement at a "Porsche shop" even when I do everything. Reasons to replace a pump also include risking a brand new belt damaging the bearing on an aging pump. It's not a "money in my pocket" thing.

[blade7]

I disagree with this, cause after 30yrs of age I do not think you should trust it to be accurate. I've since then seen issues with super weak ones being nowhere near spec.
Maybe ok on a personal car, but I always use a tool on a customer's car, and I keep records of everything being in spec.

If you fit a new water pump every 2nd belt change too, I'm glad I'm not a customer.

That's pretty much the interval that every 944 shop works by. I follow it since it's a hell of a lot cheaper to pay for a water pump every about 8 to 10 years than it is to pay me to replace everything cause it leaked.
I also charge MUCH less than a traditional shop. So I'm still cheaper than just a timing belt replacement at a "Porsche shop" even when I do everything. Reasons to replace a pump also include risking a brand new belt damaging the bearing on an aging pump. It's not a "money in my pocket" thing.

Porsche had some unexpected belt breakages very early in 944 production. And went over the top with a hastily developed solution, to protect themselves from any potential claims. So what if the belt tension prematurely knocks out the waterpump bearing, the customer pays. Over the following 35 years belt technology has progressed, but still the old tensioning/replacement procedure is used. I understand shops protecting themselves, at the customers expense. But anyone that is handy with the spanners, and is able to check the belts, tensioners and water pump bearing regularly, should think about what's really needed.

[dkofearl]

I voted for the Arnworx tensioner tool, though I also initially set up with the belt twist and feel and the water pump pulley belt friction check. I have several early and several late NAs and, given the time and cost of repairs, I just can’t bring myself to trust those old autotensioners on the late ones.
Kind regards to all,
Earl

[Tom]

So I've been working on a project to give people another option for tensioning their belts. For people who don't have the factory or Arnnworx tool, and don't have any kind of feel from how tight to set the belt, I wanted to come up with something to help. It's not a true alternative to those precision tools, but rather a handy aid for those who would otherwise be winging it. The one calibrated tool most people do have is a torque wrench, so I set out to create a tool that relies on the torque wrench to measure the tension of the belt. I also set it up to be an easy 3D print that can be done on any home 3D printer in just about any plastic (the screws add mechanical strength where needed). I've tried 4 different torque wrenches so far, including the brand new $18 HF wrench in the video below, and I surprised myself how accurate it seems to be with all the wrenches.... I'm still calibrating and fine-tuning the model, and hope to post it in the next day or two, but see below for a sneak peek.

CP tension toolcad.png (649.17 KiB) Viewed 1934 times

CP-tension-tool.jpg (382.67 KiB) Viewed 1934 times

[blade7]

I voted for the Arnworx tensioner tool, though I also initially set up with the belt twist and feel and the water pump pulley belt friction check.
Kind regards to all,
Earl

I've never been impressed with the belt twist method on a 944. Really the cam belt just needs to be sufficiently tight enough to drive the water pump with the engine cold. As soon as some heat gets into the engine, and it expands, the belt gets tighter anyway. Printed tool seems to make the expensive tensioner tools overkill too.

[355]

That a nicely designed, simple tool Tom and I can see how it should deliver consistent results. You should also try it with an old style beam torque wrench as that could be even more accurate having a nice linear build up of torque without the click back at the final torque value. Well done!

[Tom]

That a nicely designed. simple tool Tom and I can see how it should deliver consistent results. You should also try it with an old style beam torque wrench as that could be even more accurate having a nice linear build up of torque without the click back at the final torque value. Well done!

Thanks! Since this is a 'budget' tool, I went out and bought the 1/4" inch-pound torque wrench at Harbor Freight for $18.99 and was using that in the video. I just wanted to make sure that the tool worked for people who don't have fancy torque wrenches. But you're right, beam style would be good for that too and, like digital torque wrenches, work well because you can see the torque as it builds, as you say. I initially thought the click types wouldn't work so well, but they actually do fine. The tool was surprising accurate across all the wrenches I own -- even ones the old ones that are probably out of calibration and the big ones technically not accurate at such a low force. Every one of these wrenches were clearly off the marks at 7 ft lbs (84 inch pounds) when I set the tension to 2 or lower or 5 and higher. I wouldn't say it can accurately tell the difference between 2.7 and 2.8 on the 9201, but I'd argue the factory tool offers a false sense of precision anyway, insofar as the number will fluctuate a lot depending on how far you turned back the motor, how much you've moved and tested the belt in the same location, etc. At any rate, I tried all of these....

torque-wrenches.jpg (794.8 KiB) Viewed 1899 times

[gruhsy]

Nice work Tom.

Have you tried to find a place to calibrate your torque wrenches?

We send out our calibrated devices annually at my work. Talking several hundred items from wrenches to electronic equipment.
Of course it’s a requirement for the Defense/Aerospace as to why we do that. Everything comes back with required documentation.

[stitch2k1]

Nice work Tom.

Have you tried to find a place to calibrate your torque wrenches?

We send out our calibrated devices annually at my work. Talking several hundred items from wrenches to electronic equipment.
Of course it’s a requirement for the Defense/Aerospace as to why we do that. Everything comes back with required documentation.

Oh I guess I just asked a redundant question the other thread, oops. Fancy or not calibration is important. I've seen a $10 1/4" drive HF torque wrench used by my A&P IA who was a maintenance manager for a big Textron facility. It was more accurate than Snap-on torque wrenches as he told me. Meanwhile his bigger torque wrench was predictably Snap-on.

I think I'm going to invest in a good 1/2" torque wrench when Christmastime rolls around and get it checked out. Going to use that for engine building. Hopefully before I do my 911 engine project.

[Tom]

Needless to say, I like torque wrenches. I've had a few of them calibrated a few years ago (and they were predictably way off). The snap-on dial wrench is for engine assembly and gets calibrated before engine builds. My go-to is the Snap-On digital wrench for everyday wrenching.