How to Set Cam Timing on 996
 

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, and i don't have the tools. 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.

the tool wont work without removing the valve cover - 3.6 motor I assume?

I gotta think about this... you want to rotate the cams with the motor pinned and the sproket loose and hope to hit the timing right... right

actually, this is a 3.4L without variocam plus. why won't the tool work with the valve cover on?

i just checked the factory shop manual. 'fine tuning' of the cam is done with the valve cover on.

On a 5 chain not sure right now, have to dig deep in the memory.

What you are proposing can be done. For sure the timing tool fits with the cam covers in place, and yes the cam slot is parallel to the head. I'm pretty sure you can access all the sprocket bolts with the scavenger pump removed. I beleive an 8mm bolt will work as a crank lock.

Cam position is much easier to adjust with the cam covers off. The cam can be turned with a 22mm wrench, which makes it much easier to line up. If you choose to remove the cam covers, you will need tool P255 (Sir Tools, above pic) to hold the cams, as the cam cover is half the cam bearing journal. Once the cam cover is off, you need a pair of P256 (Sir Tools, above pic) to be able to hold the cam while you rotate the engine and make the adjustments. The Sir Tools kit is a good value and makes the job pretty easy.

BUT why is the timing off? It is unlikely the chain jumped a tooth ... at least not on a 5 chain engine. Did you not have tension on the chains when you tightened the sprocket? Or maybe you turned the engine backwards just a little? Chain tensioners only work properly when there is oil pressure, so hard to adjust properly without oil pressure. The factory tool that replaces the chain tensioner for this proceedure makes it much easier ... and less risky. You probably need to understand why the engine is now out of time before you tackle retiming it ... bent valves are expensive.

Also, be careful with the cam cover sealant on assembly ... to much in the wrong place and the green plugs pop out.

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. The 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.

thanks, guys. the timing is off because i had an issue doing an IMS bearing retrofit & oil pump drive installation. i had the tensioners out to do the IMS bearing. i replaced it, & all was well.

i then pulled the oil pump, went to look for my new oil pump drive, and it wasn't in the box! i put the tensioners back in w/ the oil pump off. when the new oil pump drive arrived, i pulled the tensioners, but the end of the IMS wouldn't center. somehow, there was enough slack in the chain that when i put the tensioner back in, the chain was between teeth on the sprocket. i wiggled the crank a little to try to get it to settle. it did, but it settled one tooth off.....

thanks for the replies.

Oh! I'm betting there was a lot of language when that happened. 50/50 chance and it goes the wrong way.

Good luck with the repair. What a PITA.

yea, my point to is the cams are too hard to rotate with them in place just by using the end notch (plus room is limited.

you have to make sure the tensioners are out also (right?) to rotate them - I dont think you can loosen the sproket with the tensioner in.?

chances are good only one side is off right? the 4-6 bank is fed from the oil pimp side of the IMS so that is your side that slipped.. the IMS Bearing /seal should have held the 1-3 chain in place.. just a guess but check both

It is not the chain tensioners that make the cams hard to rotate, it is the valve springs, etc. When the cam sprocket bolts are loosened, so the tensioners are not a factor, the cams are still tough to rotate. You can definitely rotate the cams with the tensioners in.

This is the method I used when I reinstalled my cams and engine. Now have over 8,000 miles since the fix on my engine and it is running strong.

both sides look off to me, but i checked their index prior to any work & they were already off a tad. Raby hinted they may have been set improperly from the factory. my bet is that the chain stretched a bit over time. either way, i plan to set both.

you're right that you can't fully remove the cam sprocket with the tensioners in place. however, the tensioners DO need to be in place for the timing to be set properly (according to factory manual).

There is also the variable of the chain tensioners. Porsche makes a set of "pre-tensioners" that go in where the tensioners are and then apply a specified amount of tension to the chains. A set costs about about $500 or $900, I forget. They have them at Baum Tools. I looked at them but the guys at Baum said they don't sell that many of them, most techs just use the standard/real tensioners. Jake Raby once also recommended that I just pump up the tensioners with heavy weight oil (put them in a bath of oil and compress them a few times) and use them. But the use of the tensioners rather than the pre-tensioners could account for a small variation, should not be more than a degree or two.

I do not favor the use of the Porsche pre-tensioners during this process.. Especially since tensioners have changed and been revised over time.

I use the engine's tensioners when setting cam timing, its been the only way I haven't seen deviations in timing after the engine ran for a thousand miles or so after the process was carried out. Most engines on the road could stand a timing adjustment, especially after 50K. The bank 4-6 IMS sprocket has a tendency to slip over time, which can create deviations that hurt fiel economy, yet generally don't through a code.. They result in a higher rough running value and I can generally note these from just sitting in the car while its idling..

thanks, jake. i appreciate the input.

what's your thought on locking the cam / rotating the crank versus locking the crank / rotating the cam?