Quick Cam Timing Reasurance Please

[1972_911T]

Ok ive just done my cam timing followed the book to the letter and must say it went pretty well. One aspect I was unsure of was in the book for the left cam it says to clamp the tensioner against the side of the housing to make sure all the slack is removed, I did this however this put alot of tension on the chain I was worried it may stretch it, I also noticed it made the engine harder to turn over from the tension in the chain but I presume when the engine is spinning the cams between 500 and 3000rpm there will be a lot of tension on the drive side of the chain.

Any way I carried on and set the timing to 1.25 spot on tightened up my bolt and did a couple of rotations to chk it was right. After I removed the clamp and fitted the hydrolic tensioner there was very little tension in the chain just out of interest I turned the engine one more time to see what difference it would make having no tension and my 1.25 value at TDC had now changed to 1.8 without any tension in the chain. obviously without as much chain tension you would expect the cam to be advanced but would you expect such a difference?

Thanks Steve

[Eagledriver]

There will be more tension on the chain when the tensioners get oil pressure. Having said that I don't like to put much more tension on the chain than is needed to take out all the slack. If using a C-clamp I tighten until slack out then a small amount more so I have to push on the cain to get it to deflect. You're trying to simulate the conditions the car will be under when running.

-Andy

[hcoles]

I agree with Andy...just put enough tension on the chain to take the slack out and to the point where you can't easily deflect it...I wouldn't recommned really killing it with tension like it sounds like you may have done.....and this caused the difference you see in killer tension vs. very little tension. I'm a bit surprised at the difference you are seeing..but I haven't really studied or tested this.
That's my 2cents.
-Henry

[1972_911T]

Thanks Guys; But im still unsure, this so called killer tension as you put it wouldnt you expect to have this sort of tension on the drive side of the chain when the cams are spinning at 500- 3000 rpm with all rockers installed?

Steve

[hcoles]

Steve,
I don't know what the average tension would be on the tension side of the chain during normal operation. If someone knows the hp to run the cam by itself we could easily figure it out. In any case probably applying a similar firm tension when making measurements to both sides compared to having the exact duplicate of the running tension is all that is needed.
-Henry