Let me tell you how much I hate cam timing

[82SC]

well I hate it...hate it hate it hate it

using BA's book, Wayne's book and bentley I do understand the concept...but I am always a hair off

the closest I got is having the Z1 notch, one notch width off...
i've been making tiny movements...but still

anyways...I been at it for about 2 hours...

I am gonna eat lunch and tackle it again...any tips and suggestions would be helpful from those who have done it before...

thanks

MJ

[jhugh]

MJ,

I just had some helpful feedback a week or so ago from John Walker. The string is on this board. Just search for cam timing - advance or retard. I decided at a certain point to go for a little advance. Conveniently enough, that's where I'd landed after adjusting the left at least 7 times. And even more conveniently, the right side lined up first try.

The most helpful comment for me was John Walker saying that within each hole, there's room for considerable movement. I played around with that and all of a sudden had much more control. Push it against the pin in one direction or the other, hold it there hard until you get it tightened down, then torque it.

Also, another thing I found was always torque in the cam bolt and the tensioners. Otherwise, you'll get wildly varying results. When I started torquing to spec each time, results got consistent.

Good luck!

[82SC]

yeah...I've realized each hole has about .5-.75 difference...

and I've been torquing the cam bolt...I tried with just the pin...and realized I needed the bolt...

I'm gonna keep trying...keep the suggestions coming...I'll check back if I still can't get it

MJ

[Superman]

Sorry for your trouble. I had a different experience. When you rotate to the overlap point, if it is not 'right,' then turn the crankshaft until you get the right lift, pull the pin, make sure the cam does not move, rotate the crank to TDC overlap and reinstall the pin into the hole that is now lined up. In theory, that should do it.

[Jadams1]

Are you using the tensioners by themselves to keep the chains tight? I used a pair of visegrips to help keep everthing tight while I set the timing.

[Wayne 962]

The spec has a pretty wide range - it should be easy to get within this range, unless something is wrong. I've never had a problem hitting it on the first or second try...

-Wayne

[82SC]

HAHAHA

well I knew the timeing spec (964 cams) was 1.26mm

and I thought it was +/- 0.01mm not +/- 0.1mm

so I have been trying to get it to 1.26mm exactly...but I've been hunting withing the normal spec the whole time.

oh well...now I gotta get the right side to be as close to the left bank now right??

MJ

[Superman]

Si.

[Wayne 962]

Yes. See cam timing not so bad after all senor!

-Wayne

[82SC]

yes...so for future reference to readers who may run across this if you're armed with the right tools (wayne's book most importantly) cam timing is easy!!!!

MJ

[911pcars]

Here's another article on cam timing.

Sherwood Lee
http://members.rennlist.org/911pcars

[Wayne 962]

Your Home - Back - Next blends in too much with the page!

-Wayne

[82SC]

yeah took me a while to figure out why he sent a one page cover for the article

BTW is there any advantage of getting the value exactly right??

also I have turned the engine many many many times and sometimes the value of the cam timing is slightly off...I'd say the values fall in a range of about 0.05mm...is that normal?

MJ

[boyt911sc]

MJ,
Follow Superman's tip. I recently did a 964 cam timing and got the spec without any trouble. Did exactly what Superman said.
Torque the cam nut sufficiently (not spec) during initial measurement. Take atleast 3 consecutive readings @ Z1 before going to cylinder #4.

[rcwaldo]

my thoughts have always been to get both sides as close to each other as possible. In other words, yeah, get it within spec and try to match the other side to the same side of the tolerance spectrum that the first cam was set at.

Time spent here is time well spent!

Chris

[82SC]

yay

1-2-3 1.25mm
4-5-6 1.26mm

I actually found I have to overshoot my target measurement, because no matter how careful I am I fub it up when I torque the bolt

now let me tell you how much I hate valve adjustments...how do you guys do it with the engine in the car???

oh and let me tell you how much I hate tightening the rocker allen bolts 10 degrees at a time

and let me tell you how pissed off I am when I found that I misplaced 4 of the 24 RSR rocker arm seals...

But it is a great satisfying feeling, sitting here, with an ache in my back thinking about the things I got done today...

back for more tomorrow

MJ

[RoninLB]

Originally posted by 82SC
also I have turned the engine many many many times and sometimes the value of the cam timing is slightly off...I'd say the values fall in a range of about 0.05mm...is that normal?

MJ

to my understanding, the drive gear teeth off the crank don't come back together w/ the chain on every 360deg spin.. I think it takes 9 turns to get the same teeth back together with the same link on the chain. mark the tooth and link w/magic marker to confirm. which is a PIA.. so 9 turns latter you are back to same tooth/link, but on valve 4 timing.. so do another 9 to return to valve 1 timing.. I don't think anybody around here does this but me.. so I figure a ballpark number +/- from original setting is routine.. not a pro, so no hard +/- numbers.. the links/chain are not extremely precise, IMO.. and there is gear/chain wear.................Ron

[ChrisBennet]

Originally posted by 82SC
yeah took me a while to figure out why he sent a one page cover for the article

BTW is there any advantage of getting the value exactly right??

also I have turned the engine many many many times and sometimes the value of the cam timing is slightly off...I'd say the values fall in a range of about 0.05mm...is that normal?

MJ

It's a good question. I am able to get fairly repeatable values like: 1.24, 1.25, 1.25, 1.26, 1.25, 1.25, etc. - much closer than .05mm.
Too little tension on the chain and too much lube on the cam shaft can cause inconsistent values in my own limited experience. I've said it before, the very essence of accuracy is repeatability. You should alter your procedures until you can get repeatable measurements.
-Chris

[911pcars]

"Your Home - Back - Next blends in too much with the page! "

Picky, picky,
picky.

Okay, you can navigate now

Sherwood Lee
http://members.rennlist.org/911pcars