993 cam timing and tensioner question

[pete911]

I am putting my engine back together. I have timed the cams using the factory tools. What puzzles me is this. As I turn the engine over with all the rockers in place the chain tensioner "collapses" 3 times on each side during a full firing cycle of 720 degrees of crankshaft rotation. This happens with the tensioner tool in place, as well as with the normal tensioners in place. I realize that if the engine were running the tensioners would "pump up" due to oil pressure. I did use racing springs that have a higher spring rate. Could this be causing this? Has anyone seen something like this before?

Pete

[rsscotty]

We use the special tools shown on the top left in the following link. Never tried it any other way.

http://www.baumtools.com/pdf/porsche_timing_tools.pdf

[pete911]

I have these tools, and that is what I used. After I set the timing I removed the "jigs" and turned the crank by hand. As the cam reached max lift for each cylinder the tensioner collapses. I think the heavy duty racing springs are trying to stop the cam, so the tensioner collapses. As the cam goes over the point of max lift the tensioner then snaps back. I took all the rockers out on one side and the problem went away, so this is definately the source of the problem.

Pete

[Eagledriver]

I'm not familiar with the 993 set-up. Can the tensioners be "primed" with oil?

-Andy

[geolab]

in my experience , it is normal, and whilst the tensioner collapses, the bottom part of the chain gets loose. Are you using the special bolts for the timing tools ?
I am looking to buy tensioner tools if anyone has a pair, and front cam holding wrench. thanks

[pete911]

Geolab

Thanks for that confirmation. I used normal 6mm bolts to hold the tools in place. After I was done I went back and used a dial indicator and an old mechanical rocker to check the timing. The side to side difference between #1 and #4 was .001 inches, so as far as I'm concerned the tools worked perfectly. Many people that I spoke to said the most important thing when timing the cams is to get both sides the same and that was clearly accomplished in my case.

Pete

[geolab]

Originally Posted by pete911

Geolab

Thanks for that confirmation. I used normal 6mm bolts to hold the tools in place. After I was done I went back and used a dial indicator and an old mechanical rocker to check the timing. The side to side difference between #1 and #4 was .001 inches

great , if you want to sell the tensioners, i would be interested soon, thanks

[pete911]

Sorry, but I'm keeping all the tools. This won't be the last time I'm into a 993 engine.

Pete

[dgmatt]

I just timed my 993 using the tools and had the same issue with the tensioners collapsing. I also have racing springs. What surprised me was how much harder it was to turn the crank when I installed the hydraulic tensioners and all the rockers, making me think that perhaps I didn't use enough tension with the manual tensioners.

You said you had only a small difference from side to side, but do you have the actual measurements? I'm going to measure mine and curious to see how close the figures are.

cheers,
Don

[pete911]

Like I said in the earlier post the side to side difference was .001" using a dial indicator and an old style mechanical lifter.

Pete