Changed wear pads, variation is worse

[Gary_d]

I changed out the cam wear pads and chains, Bank1 variation is now great. Bank2 however, got much worse.

Before change:
Bank1= 4.30
Bank2= 6.14
After change:
Bank1= 1.6
Bank2= 11.64

Did I possibly skip a tooth on that cam chain while it was being put back in? Went through the procedure for cam alignment and all looks good.
Ideas?

[Jake Raby]

I bet you didn't pump up the tensioners before putting it all back together.. It always hurts bank 2 when this occurs.
Also did you roll the engine over at least 10 times and then check the cam timing by fitting the tools on both banks? This is a requirement, or bank 2 will also hurt. Bank 1 looks fine.

[Gary_d]

Jake, you're absolutely on the money. Would I expect less...?!
I simply changed out the chains and pads, no 'pumping up'. On the timing, I followed the primer on the forum, so probably only rotated about 4 times or so, eyed the alignment of the cams.
I guess the question now is, what's my strategy to fix it? Bank2 cover back off and?

[Gary_d]

Jake, just reread your answer and I think I misunderstood. Got it now. When you said 'tensioners, I was hearing 'actuator'. Couldn't figure out how to pump it up. As it turns out, I did replace all 3 tensioners with new, updated versions. Put them in right out of the box. I'll pull those, one at a time and prime them. Correct?

[NewArt]

Good to read this! I'm at this stage as well, where I will be reinstalling the cams with new pads and chains in the next couple of days. Hope I get it right!

[Jake Raby]

This is where my book will be gold for you guys..

Yes, you must pump the tensioners in oil and then install them immediately before setting cam timing.. Or use the Porsche pre tensioners that are insane money.

These engines will teach you many, many lessons...

[RawleyD]

I always love hearing JR explain things. so cool and experienced.

[philou320]

Interresting, but I have read that:


These tensioners are one of the most mis-understood items on these complicated 911s. Firstly, they are not oil-pressurized tensioners, they are oil-dampened, which makes a huge difference. That means they are spring-loaded and then oil filled to dampen them (like a shock absorber) during operation. I believe that the oil dampening reduces the spring-back effect of the natural spring inside and helps to keep tension on the chain and prevent "bouncing" of the chain tensioner against the wheel.

so the pressure applied during the timing setting should be enough..

[eicheldp]

Originally Posted by Jake Raby

This is where my book will be gold for you guys..

Jake,

Any info on the publishing date?

[Gary_d]

As an update, the tensioners were the problem. Hate to admit I did it, with my background I should have caught that.
I pulled the tensioners one at a time and pumped them up. Huge difference in the tension. Rotated the engine a number of times to be sure the full tension was on the chains, then set the timing.
Final specs on the deviation,
Bank1= 1.59
Bank2= 2.10
I'm Ok with that
@Philmou320 - You're correct in that they are 'suppressors' not 'depressors', much like a shock absorber or lifter. The fact that they are not in dampening mode lets the chain float enough that the timing is near impossible to get spot on.

[philou320]

So I understand that you have to pump them when you put new ones or you have let them for a while bleeding out the oil but when you want to set you timing and they are still on the car, do you have to pump them too?

If the car has run for a while, meaning that the oil is supposed to have filled the tensionners and the visual control of the timing is OK it should mean that everything is Ok, am I right? so Gary, When you checked your timing, were you camshafts perfectly parallel to the seam between the head & the valve cover after -1-the repair AND after a ride?

thank you .