Camshaft timing Part II

From pcarworkshop

In this article we will continue installing and timing the camshafts. Here is the postive locking pin for the camshaft timing gear.

Here are both chain ramps and I am ready to put on the main sprocket. Notice the holder that I am tightening up...it provides the pivots for one of the chain ramps.

The chain tensioners should not be used to set the timing but substitued with mechanical ones...so I built one. I used an old piston brake caliper spreader and cut it up...worked like a charm!

In order to set the timing an old style rocker needs to be installed. Here are the to rockers (the one on the left is the new one, the one on the right old style). I had to grind the older one to fit since the rockers are narrower on the 993...other than that its $5 at the wrecker..

Ahh, the old fashioned setting of the valve lash. The lash is set to 0.01 mm(or 0.004") in preparation for setting the timing. This is pretty well what has been done on every 911 before the 993...and why I have the tool for it since I had a 83SC before my 993. The lash is the "slack" between the valve top and the rocker when the cam is not pressuring the valve.

Here is the cam timing tool setup for timing. You are measuring the amount the intake valve is depressed at top dead center (TDC) of the intake cycle. This amount for our cars is usually 1.0mm and can go to 1.2mm if you want to advance the cams. Its a challenge to mount the gauge since the conventional Z tool usually used for this does not fit on the 993...they changed the design of the cam towers.

The indexing pin can be pulled out with either an expensive Porsche tool or an old sparkplug...which one did I use ?  :)

OK, timing is set and the cam is torqued down to 88 ft lbs. Notice the fancy tool to hold the cam still ; you do not want to load the chain system for this so the tool holds the cam still while the torque wrench is being reefed on...its simpler than it sounds.

OK, timing is done (after a few hours of adjusting and cursing... ) and its time to put the chain tensioners back in. Here is a shot of a chain tensioner..the cap that feeds it oil and holds the tensioner in place is on the right.

Here is the tensioner in place holding up that chain ramp...what is amazing is that the chains are kept tight by plastic ramps that were in pretty good shape on my car...

Time to put in all the rockers back in and of course change out the hydralic lifters. Lets take #2 as an example. Question : how do I tell that this is an exhaust or intake rocker??

The lifter has to be pulled from its rocker where it spent that last 10 years and several million cycles doing its job..

All the sealing oil O rings wre buggered...here is part of one that was left behind when the lifter was removed.

Comparision of the old vs. new. The biggest difference is the size and condition of the sealing O ring.

Putting a new lifter back into the rocker arm...it slips in with some pressure. Nice tight fit (after cleaning the rocker of course, blowing it out with compressed air, and lubricating the O ring).

The rocker is being installed.

All the rockers are in...

Now the chain covers to cover up those prefectly timed cams...

And its starting to look like an engine with all the essentialls covered up!!

Links to Rebuild Tour

1. Getting started, dropping the engine and superficial stripdown
2. Checking the default timing and Cams
3. Looking at the heads and the SAI passages
4. Valve guides, valves and carbon
5. Further Dissassembly
6. Exploring the SAI passages
7. Cleaning and getting ready to put it all together again
8. Rods and last minute checks before putting the case together
9. Sealing the case (or tomb)
10. Putting the pistons/cylinders back
11. Camshaft timing Part I
12. Camshaft timing Part II
13. Messing up a clean looking engine
14. Not quite there
15. Cranking it up