Cam Trouble

[boxster_s_boy_34]

Okay, so I had a thread earlier about a cam jumping timing that I thought was my fault. Well, as it turns out the cam gear will not stay torqued to the cam. I don't know if this is through any fault of my own or if this is just a bum cam, so I was curious if anybody would have any thoughts on what is going on?

[seningen]

I assume you are talking about the gear that has slotted keys
and the bolts go through here and screw into the exhaust camshaft.

This is a very surprising design to me.

Maybe it was to allow for tolerances in the chains or what not to allow
for proper alignment.

I've read -- but have not seen where they replaced that part.

I guess optionally you could replace the bolts, use some locktite,
or even spot weld them in place.

Mike

[Jake Raby]

The cams are powdered metal.. The threads inside the drive flanges are weak, when they strip they have to be oversized or the cam has to be replaced.

I have good used cams.

[boxster_s_boy_34]

Thanks Jake. Not really what I wanted to hear, but I guess that I'll have to go check the threads and see what's going on.

[boxster_s_boy_34]

Maybe I didn't word this problem correctly. The cam gear on the intake camshaft will tq to 45 ft lbs, however it will not stay at that tq spec it loosens itself up. I can't even turn the motor over by hand without the gear losing tq and spinning freely.

[extanker]

its not keyed ?

[boxster_s_boy_34]

The intake cam on the gear side is not keyed that I am aware of, but I'm thinking that maybe I need to pull it back out because I may not have the gear completely seated.

[brp987]

I haven't worked on boxster engines, but have built several air cooled 911 engines. These scenarios come to mind:

1. there may be a blob of thread locking cmpd in the cam at the depth the bolt would reach its torque value leading to a false reading.

2. the threads in the cam are yielding and there is a dislocation at the depth the bolt would reach its torque value leading to a false reading.

3. the bolt is bottoming out

4. the bolt is not stretching due to work hardening or insufficient torque


When you tighten the bolt does it tighten gradually or does it basically stop and the torque spikes up?