JCP911S

I am setting cam timing on my 3.0 SC engine. Everything is going fine except when I torqe the big cam retaining nut to spec.

My spec is +/- .1mm... but the setting "walks" more than that... and what's worse, it does not consistently "walk" in the same direction... sometimes its lower, sometimes higher... so I can't seem to correct for it.

My chain sprocket is brand-new and the lock pin fits very tightly... I just cannot believe there is that much slack...

What's up?

Peter Zimmermann

Common problem - you have to counter the torque applied by equal and opposite force using your holding tool. Hold your torque wrench and holding tool close to each other, and torque your fastener by squeezing/pulling them together. If it still moves you will have to move your pin to the next hole and try again...

JCP911S

Pete,

Thanks... I was afraid you you we're going to say that... so far that is the concensus....

Good side... I'm not doing anything wrong

Bad side... I'm not doing anything wrong

Guess I could waste ALOT more time doing something alot more productive... but if that's the game then, I'm ok with it....

Just don't want to feel I'm much more stupid then I usually am...

JCP911S

BTW... for extra credit and just for fun.... what is it in that system that creates so much varience...?

On paper it should lock... why does torque on a fixed system with a thrust washer create so much radial movement?

The gogs seem to be fixed together.... is it flex in the chains?

SeattlePorsche

It doesn't lock. It just puts you in the neighborhood. Watch your dial indicator as you tighten and counter torque. You don't want it to move. There will come a point where you just got to give it hell with the torque wrench, and then hope that you are in spec. Fortunately, you get better with the second try, then the third, then the.....

But when you do get it right, you are stoked!

JCP911S

Yeah.... pretty much what I've found... and pretty much what I figured...


But... for extra credit.... why does that system cause that problem?

I'd expect the pin to hold everything in state...

Why does torquing the nut cause things to move?

What is the soft-point?

I'm thinking the timing chains...

Theories welcome...cause, boy I'm curious

JCP911S

Thanks alll!!!

Good to know I'm not doing anything wrong...

Hey... I got nothing better to do the next 8 hours of my life.

Peter Zimmermann

Like Seattle said, when it's right, and torqued, it's a really good feeling!

Believe it or not, there is enough movement between the chain wheel and the cam gear, even with the pin in place, that you might think that you're OK, but the pin actually belongs in the next hole. If you have a tool in place that simulates the action of a tensioner the chain will have no effect on timing. Have fun with it!

Barry A. Waters

JCP911S,

While I can't give you any technical advice on your issue I just HAVE to commend your 'Bulldog' approach to 'getting it RIGHT'!.

Kudos to you my man! You are really asking the right questions and 'digging' to make sure you do a proper job. Hang in there and good luck. You've got some GREAT folks looking over your shoulder.

Barry

Toby Pennycuff

Wow! Someone needs to take your whaletail away from you! I swear, I put 10 miles on my 930 motor trying to time the cams properly - 720 degrees at a time!


Toby