964 wide-open throttle cam

[ischmitz]

Today I continued with some long-due maintenance on my 964 3.6 engine. When inspecting the throttle body I found that my WOT cam on the throttle body was snapped and I wasn't getting the WOT signal to the DME anymore. See below for a couple of pictures.

It appears the plastic piece is simply pressed onto the shaft. Fortunately I had another throttle body so I am back in business. However, it seems overkill having to replace the entire throttle body if just that cam is damaged. I am wondering if this is simply plastic getting brittle and this is happening a lot given that the 964 engines are coming of age. There isn't really anything to adjust and without WOT I probably leave some power on the table.....

Does anyone know if these cams are available separately?
Is this a common failure?
Should I attempt a JB Weld fix?





Ingo

[Vandit]

This thread discusses a couple of options to remedy this known problem.

Either (a) glue it back together and safety wire it, or (b) contact the guy who machined an alloy replacement and ask if he'll sell you one.

Source for WOT cam actuator needed - Rennlist Discussion Forums

[ischmitz]

Yup, found that thread, too after some searching. I am actually tempted to try one of these online 3D printer outfits. You upload a design and they send you the item 24h later via FedEx.

Ingo

[Tom '74 911]

Hi Ingo,

That same piece broke on my '90 3.6L engine. I sourced a good used one from PartsHeaven or some other similar place if I remember correctly. I considered wiring the broken one as suggested in the Rennlist thread, but decided that replacement was a better option for me. I think I paid like $5 for the used one...

Tom

[ischmitz]

Tom,

given that there is nothing really acting on the cam other than the little lever from the micro-switch it didn't take much if any force to break it.

I believe these all will fail due to the plastic aging. The softeners diffuse out of the plastic making it brittle. So getting another used one might just ask for another failure soon down the road.

Machining a piece out of aluminum like the guy on rennlist or rapid 3D printing would be more permanent IMHO. I wonder how many 964 are around today with this cam spinning around freely on the shaft?

[Tom '74 911]

Originally Posted by ischmitz

I believe these all will fail due to the plastic aging.

I think you are probably correct in your thinking.

For myself, I have never had much had success gluing anything plastic... maybe I'm not using the correct glue. I have done my share of drilling small holes through broken plastic parts and wiring the pieces together - with success, but that's not the cleanest solution either. While a piece machined from aluminum or 3D printed would be great, I don't have easy access to either of those methods at the moment, so I figured a good used one would work for a while. $5 seems like a lot for such a small piece, but I think that was their minimum charge or something if I remember correctly. I bundled it in with a few other parts & pieces to help amortize the shipping as I live in the boonies!

If you are able to get some pieces machined or 3D printed, let me know!

Happy New Year,

Tom

[Tom '74 911]

Also, I looked in PET and didn't see that part listed separately. I wonder if it's in the parts kit though: 964 110 970 00 or 964 110 970 50