Cam Timing Question

[jonesb930]

I will be timing the cams in my motor this weekend. I have Wayne's book and I have read the chapter on doing this. Here are the specs from the sheet that came with the cams (Webcams)

_____________________________________________
Engine Porsche GT2 "EVO" (Mech Rocker)
Grind# 563/564
(Set @ 2.3mm with .10mm Lash)

Valve Lash Intake: .004 / Exhaust: .004
Valve Lift Intake: .480 / Exhaust: .460
Duration Intake: 264 / Exhaust 250
Duration @ .050 Intake 248 / Exhaust 236
Lobe Center Intake: 111 / Exhaust 111

Intake Opens 13 deg. Before TDC
Exhaust Opens 49 Deg. Before TDC
Intake Closes 55 Deg. After TDC
Exhaust Closes 7 Deg. After TDC

Valve timing is checked with zero valve lash @ .050 inches of valve lift
__________________________________________________ __________

In the Chapter it stated that if the intake valve stroke in overlapping TDC with .1mm valve clearance is more than 2mm to use the "High-Lift, High-Duration Timing" method. From my sheet it appears that this is the method I must use.

Here is my issue: Once you get the crank back to TDC you need to back off the cam bolt and turn the cam while keeping the crank at TDC. On the older style camshafts with the large 46mm nut you can use the cam tool to accomplish this. On the later style cams with the cam bolt how to you turn the cam without moving the crank?

[Walt Fricke]

Bill

I've wondered myself. When I got an '82 SC engine for my car, I purchased the holder tool for the new style cam bolt system, expecting to have to use it. Turns out my 3.0 has the old system, so I didn't get to try it.

Reading Bentley, it looks like you do the same initial timing using the punch mark on the cam end. Then you rotate crank 360 mas o menos, until you get the overlap you want, which won't have the crank at Z1. Then remove bolt and washer, pull pin, and turn crank until it is at Z1. Reinstall pin and hardware, tighten, and recheck.

Sounds simple. IF the cam stays put with a valve spring pushing on it and nothing holding it!

So I'll join this to listen. There has to be a way.

Later stock cams have a groove in the other end, and a tool fits in that groove and bolts to the cam carrier in just the right location. Duck soup for stock cams at stock settings. But that was later.

Walt

[jonesb930]

Walt,

The method you described is for a low lift/duration camshafts. This is doable with the newer style camshafts since you are turning the crank to the desired setting. On the high lift/duration camshafts the process is different according to the book. You turn the crank 360 degrees back to Z1 and then remove the bolt and pin and finish by moving the camshaft to the desired reading. With the newer style camshaft there is nothing to grab onto to turn it. The left side is set up for a turbo scavenge pump so I could bolt on an old air pump pulley to the other end and easily turn it. The right side is another story.

[lindy 911]

It's not hard to do with the new style cams.

1. Start with the crank at TDC for #1.
2. Set the cams with the dot or key-ways straight up.
3. Pin both cam sprockets.
4. Rotate crank 360 degrees.
5. Check dial indicator on #1 intake for proper lift measurement.
6. If change is needed, hold sprocket with cam tool and unbolt leaving sprocket on the cam.
7. Reinstall the bolt WITHOUT the big washer, again holding the cam with the cam tool.
8. Snug the bolt up then pull the retention pin.
9. Adjust cam to proper lift measurement and reinsert retention pin.
10. Remove bolt and reinstall with large flat washer.
11. Move to right side (4,5,6).

Make sure you only have the #1 intake rocker in place until you move to the right side and then only install the #4 intake rocker. You will notice that the holes for the retention pin are a sloppy fit and you will need to fiddle around to find the right one. It will look good until you tighten the sprocket bolt and then it move. Stay with it and be patient. The right side will be easier.

Lindy

[aws]

The main problem I have had with the late model style of cams with aggressive profiles has been the cam will not stay in place on the ramp when you remove the pin in order to rotate the crank to the Z1 mark. It helps to assemble the rocker dry so there is more friction to hold the cam in place, but with a high lift cam they still have a tendency to rotate so I have gone to assembling a exhaust rocker with no lash to better hold the cam in position while the crank is rotated. I also bought a 3 prong cam tool for the late model cams like Walt years ago and have yet to figure out how to use it. It took a while for me to understand that on the early cams you move the cam to get adjustment and on the late style you move the crank. (this was way before Wayne's book) It is beyond me why Porsche changed the retention method, my bet it was the Bean Counters running amuck. What has exasperbated the problem is the the price on the old style billets from China have gone up in price and the aftermarket cam grinders are not using the old style as a result (as per Camgrinder)

aws

[rennsportt]

I timed the cams in my 3.2 last weekend and had similar issues holding on to the cam.

Initially I tried the spacer-instead-of-washer method, but eventually ended up doing it this way:
1. Cams both set up with keyway up and crank at Z1
2. Rotate crank to TDC overlap for cyl #1, record measurement
3. Rotate crank to a neutral point on cyl #1 intake lobe
4. remove cam bolt, move cam gear one pin location in direction of needed change
5. torque cam bolt with washer
6. rotate crank to TDC overlap, record measurement
7. adjust as necessary, then do the same for the right side cam

This worked really well, and completely eliminated fighting the valve springs.

Hope this helps.
Mike

[euro911sc]

Hey Bill!

I had the same issue. when I turned the crank the cam would move right along with it. So I reversed it. I held the crank and moved the cam by using a small screw driver through the pin holes of the sprocket. Find a hole set that overlaps a lot and gently pry the cam in the direction you need it to go. It took more iterations this way i am sure, but it worked great.

I would stop by and help this weekend, but I have to get my wheels assembled and the car prepped before going to PBIR on Wed. night. Damn BBS RS have 34 bolts a wheel... Now I know why they went to 20!

Best regards,

michael

[jonesb930]

Michael,

I had a similar idea and this may work. This issue sounds like a perfect time to make a new tool that will attach to the cam and allow easy adjustment until the pin is installed. I may not be timing them this weekend after all. I am missing the extension pin for one of my dial gauges. I should have that resolved before next weekend though. Good luck at PBIR. Are you running during the day on Wednesday? If so I would love to tag along and take some pictures if possible. Let me know asap so I can schedule it though.


Bill

[Walt Fricke]

Bill

You started a useful discussion. It does make me wish I could still use the old style big nut on the new, aggressive 4 journal cams I hope to purchase. This new system looks to be a PITA absent some way to grab the flywheel end of the cam.

I see three methods listed for the bolt end cams:

a) unpin, move crank, repin, see how it worked. Repeat until you decide to call it good enough.
b) use bolt without washer to turn cam. Sounds good, but if you torque it enough to turn the cam counterclockwise, what will happen when you go to take the bolt out? I guess that by then you have the pin in, so the chain and crank will hold things.
c) pry in the teeth of the inner wheel through the pin holes on the outer. This looks like it has promise also.

The pin really doesn't locate things precisely. On the old system I can insert the pin, and then turn the cam enough so that, on a stock SC cam, I get 0.015" change one way and the other without the crank budging. So the final step, with the pin in a decent location, was to hold the cam right where you wanted it, and tighten the big nut up very snuggly. With luck, things only changed a few thousandths. The final torquing after that didn't change anything.

Looks like those days are over for the bolt end camshafts. Gone are the days when I could retime a cam with the engine in the car and all rockers installed.

Bean counters, indeed. A pox.

[Hcarraro]

Very interesting and timely thread.

Henry

[MBruns]

Have you looked at our adjustable cam gears, they work very well for agressive cam timing and also quick for doing timing changes on the dyno or at the track.
Take a look at the web site JBRacing.com give me a call if you have questions

Mike Bruns

[304065]

Originally Posted by MBruns

Have you looked at our adjustable cam gears, they work very well for agressive cam timing and also quick for doing timing changes on the dyno or at the track.
Take a look at the web site JBRacing.com give me a call if you have questions

Mike Bruns

Mike, what is the principal advantage of adjustable cam sprockets? It seems like it makes it easier to change timing because you don't have to deal with applying torque to the cam nut (or bolt) which can throw things off.

A couple other cam timing observations to add (I finally did mine last weekend)

1. A TDC dial indicator would be a big help. I found it challenging to reliably and repeatably establish TDC by aligning the Z1 mark with the notch in the case. Eventually I used a razor blade wedged in the case parting line, projecting out over the pulley, about 1mm away from the pulley edge, to precisely align the mark. That said, MICRO movements of the mark were responsible for fairly big swings in the lift measurement.

2. The old Sir Tools cam socket has a TON of slop between the socket and the end of the cam. It is by no means a precise fit, which meant there was some slack that had to be taken up with the breaker bar before the cam could be turned.

3. Old Mahr gauges are fun collectors items, but there is nothing better than a pair of Digital Mitutoyos for this task.

[Walt Fricke]

Mike

I was so comfortable setting the older "big nut" cams that when I first saw your adjustable sprocket a few years ago I thought it was a part in search of a purpose.

Shows how narrow my background was - looks like this should resolve all the timing issues with the newer "bolt" style cams.

Walt

[Walt Fricke]

John

I've sometimes thought I ought to install the alternator and fan housing when timing the cams, because the timing mark on the housing is so much closer to the mark on the pulley. But then I think of the variables involved, and always conclude that little is to be gained. If the fan housing is already in place, of course I use that mark anyway.

I keep thinking of making a pointer I can attach to the bare case so it protrudes over the Z1 pulley mark exactly in line with the parting line. Or, better, with an established TDC referenced to the pulley notch.

I've used the razor blade. If the pulley has a V groove on each cheek, you can sight across the two like a rifle sight to the case parting line.

And establishing an accurate TDC (independent of existing marks) with a dial indicator is not simple, as you really need to measure a bit before TDC, and then an equal amount after, and split the difference. And do that before the heads are on.

After reading some suggestions, I once got an accurate TDC and marked the flywheel. But I didn't have a good case reference for that, and grew to distrust the one I had cobbled up. I still think this system has merit, but it is also less convenient to be looking at the flywheel side of the engine.

So I usually muddle along with the normal way.

Walt

[MBruns]

When timing the big cams they really make it easier, not to mention you can quickly make changes, I know that the stock gears are adjustable and I have built 911's for a living going on 33 years and it is a challenge to get them just right while torquing the nuts/bolts, frankly when you get them set you don't have any interest in testing other settings, when I mock up an engine to set valve to piston clear. in the range of cam timing that will be tested I set the sprocket bolts in the center of the slot and can easily adjust the entire range without removing the sprocket, and with the bolt style once you have it torqued it now becomes the way to move the cam.

Hope this helps, Mike Bruns