Cam Timing - I Goofed

[insite]

ok, i goofed. i ran into a bit of trouble, and after an IMS bearing retrofit & chromoly oil pump drive installation, my cam timing appears to be a bit off.

i need to re-time the cams (1999 3.4L) and i don't have the tools. i may have jumped a tooth during R&R of my IMS bearing & installation of a new oil pump drive. here is my plan; if this will not work, i'd love to know why!

1. lock motor to TDC (notch on end of bank 1-3 faces outward)

2. remove bank 1 oil scavenge pump

3. loosen sprocket bolts

4. rotate exhaust cam so notches are parallel to edge of head

5. tighten sprocket bolts

6. re-install scavenge pump

7. rotate engine 360 and lock crank (notch on bank 2 faces inward)

8. remove scavenge pump & loosen bolts

9. index exhaust cam to head just like bank 1

10. button everything back up.

the special tool (9612) doesn't look like it does anything but rotate the exhaust cam so the notches are parallel to the head. am i wrong?

finally, if i do wind up buying the tools, will the Sir Tools P253 SET the timing, or just lock it? i ask because it doesn't have a sword bolt like the porsche 9612. thanks for the help.

Edited October 1, 2010 by insite

[Dharn55]

The technique you will have to use will be a little different than you have described. Basically you are going to have to line up the cams visually with the crank at TDC. I did not have the tool and you can do this without it.

First a little background. Tthe ZDmax/SIR tool is a little different than the OEM tool. The OEM tool locks into the intake cam access hole, not the cam itself, and them fits into the grooves on the exhaust cams and allows you to rotate the cams into position (assumes that they are relatively close to the correct position. So you lock the engine at TDC, fit the tool, loosen the sprocket and rotate the cam to the correct position. then you tighten the sprocket bolts to set the position of the cams. This is done on one side, the the crank is rotated 360 degrees and the other side is done.

With the ZDmax/SIR tool it just locks in the cams with the grooves straight up and down so you have to rotate the crank until the grooves are straight, install the tool, them loosen the bolts on the sprocket, move the crank to TDC and tighten the sprocket bolts. Then do the other side.

First, how far off are you? If you are fairly close my technique will work. You can't really lock the crank at TDC and then loosen the sprocket bolts and turn the cams as with the valve springs, etc. it is hard to rotate the cams, lots of pressure. When I had my cover off I used a pair of vice grips (kind of crude) on a non-critical part of the cam to rotate it close to position, but this is not possible with the covers on. I even tried to make a tool by modifying a socket to fit into the grooves on the end of the exhaust cam, but even with this and a socket wrench it was not possible to keep enough pressure on the socket to keep it in the grooves and rotate the cam.

With the cam cover on and the cams close to the correct position here is the technique that I used. Choose which side you want to do first and get the crank at TDC with the cams on that side close to the correct position. Use a socket on the pulley to rotate the crank ( this is how I did it although Porsche makes a tool that fits into the pulley to rotate the crank). Then rotate the crank slightly to get the groove straight up and down, the crank may not be at TDC. (As an aside, I saw one article that said to never rotate the crank in reverse, but I can't understand why this would damage anything and here we are talking about only a few degrees of rotation.) It can be hard to make sure the grooves are lined up perfectly straight up and down, use a straight edge and the joint between the head and the cam cover as a guide. Once the cam is set loosen the bolts on the sprocket, then rotate the crank to TDC, should only be a few degrees, lock the crank at TDC. Hopefully the cams have not moved. Now tighten the sprocket bolts. I tightened two of them, then put loctite on the other two and tightened them to torque, the loosened the first two and put loctite on them. Now that side should be set. Rotate the crank 360 degrees and use the same technique on the other side. This should get them about as close as you can without the special tool. You need to be fairly precise as 1 degree at the cam is the equivalent of 2 degrees at the crank.

Sorry if this write-up is a little disjointed but it is late and I have cut and pasted it from an email I sent to another owner. Let me know if you have any questions. By the way, if you are not going to remove the cam covers you do not need to buy all the tools in the SIR set, which is very expensive, you only need the tool at the top left of the picture. You can use a torx of the proper diameter to lock the crank. The other tools shown are to hold the cams when removing the cover and when removing the cams.

Edited October 2, 2010 by Dharn55

[insite]

excellent; thanks. i'm actually pretty close on timing, but it's off enough IMO to affect the way the car runs. i actually think it was a little off to begin with. i put match marks on the head at TDC before i pulled the IMS bearing & oil pump. the cams were NOT perfectly vertical prior to having started my work......

BTW, the reason they say not to rotate the motor backward is that the chains lose tension & bad things can happen. if you only go a couple of degrees, this no big deal, but if you go far, you can jump a tooth on a chain pretty easily. looking at the factory manual made this really start to seem much easier than most people make it out to be. i've done lots of other cars, and they're all pretty straight forward. didn't see why it would really be any different here.....

with variocam plus, i'm sure it's a little more involved, but probably not rocket science. thanks again.