Woodman71

Goodness me. One more thing I don't want to think about.

p.vanderlinden

I'm really surprised they use slots for the fasteners?

Must be a "one size fits all" Porsche cam sprocket

Ahsai

Yup, I asked the machine shop to magnaflux them. They found cracks on the bank 1 cam sprocket, caused by metal ingestion in the bank 1 scavenge pump. Just ordered a new one from Sunset - $160 for a freaking sprocket

The slots are for adjusting the cam timing.

Also got my rotating assembly back from the machine shop. They said it's balanced to 1g-in (0.03 oz-in). I asked if they meant 1oz-in but they said it's really 1g-in. Sounds too good to be true?

Woodman71

I feel like I've read this thread 5 times, but still can't recall - what was your original failure attributed to again?

Ahsai

I sent in the failed IMS, IMSB, all the timing chains, and all the debris I found to LN for further analysis and their conclusion was the failure was due to stretched timing chain between the crankshaft and the IMS.

The bank 1 scavenge pump ingested the debris and was chewed up inside. That put a lot of pressure and shock on the bank 1 cam sprocket that drove it.

Woodman71

I mean, that's just bad luck, right? Nothing you could have done differently to avoid this kind of failure?

Noz1974

Ahsai
I got a spare cam sprocket from my original engine could have posted over to you, is it too late to cancel your order?? I'm in uk so might take a week or so to reach you though??

Noz1974

I don't think the timing slipped, if you look at the paint on the right hand bolt it lines up with the paint on the sprocket, I think this engine has had its timing reset before at some point, the mark you see was probably the original factory setting but I'm pretty sure it's been changed at some point?? Doesn't the paint indicate an engine returned to the factory under warranty for rebuilding or was that blue paint, I read that somewhere ?? Wonder if Porsche recorded the engine numbers or recalled cars and details??

Woodman71

IIRC, the blue paint was from the factory, when an engine was inspected and returned to the line because it wasn't up to snuff.

Ahsai

Sorry for the suspense. The yellow paint was put on by my machine shop to show me where the cracks are. They removed it from the cam to magnaflux it and put it back on the cam randomly hence the random bolt locations.

The failure was probably due to bad luck but the only way to prevent timing chain failure is to replace them.

Noz, thanks for your offer but I think I'm good for now as I ordered it last week and it's already on its way.

Woodman71

When do people generally do such a replacement, out of curiosity?

Ahsai

Jake offes a preventive maintenance package that includes changing out the timing chains (the ones between the crank and the cams) w/o splitting the block. In this case though, it's the ims chain that's between the crank and the ims and that requires splitting the engine case to replace so most likely it only makes sense if you're doing a full engine rebuild.

Byprodriver

Stop driving the car when the noise 1st started!

Woodman71

The noise being...

Ahsai

Check out post #44.