: '94 SLS, 4.6L, how do you set the cam alignment?

07-17-05, 07:23 PM
Hi All,

I had the white smoke problem, and pulled the left,(front) head off.

I marked the postion of the cams and sprockets, but when the head shop checked the head, they cleaned off my marks.

Now I have reinstalled the head, and I looked at the manual I have and it says, take it to a shop to have the cam/sprockets/chain worked on.

The engine is in the car, the 4.6L seems to have no timing marks like the older 4.9L. Do I turn the engine over until the #1 piston is all the way up, for top dead center, then turn sprocket for the intake, so the "FI" is up, and turn the sprocket for the Exhaust so the "FE" is facing up and get the chain on?

How do I get the chain back on? with the chain tensioners off, will the chain slip back over the sprockets?

thanks for the help

07-17-05, 10:36 PM
You have a lot of work to do. There is no easy way out of the situation you are in.

You must tear the front of the engine down and remove the front cover to access the cam chain tensioner for the front bank. When you released the chain tension the tensioner extended due to the spring inside it and it has been trapped in the fully extended position by the mechanical rachet in the tensioner. That is the first problem.

You MUST do this as the tensioner has racheted out and will be too long to allow the chains to be installed. If you force it on the excess tension will cause the chain and guides and front cam bearing on that side to fail.

You can get the harmonic damper off the crank by working thru the wheel well on the right side. Remove the front cover and you will be able to see the timing marks on the chain drive to work from. The harmonic damper is quite tight on the crank and will take a serious puller to remove it.

You will have to turn the engine over until number one is at TDC to reset the cam timing on the left head. Number one is right front corner of the engine..i.e...the rear cylinder on the front of the engine on the passenger side of the engine compartment.

When you do this the timing mark on the sprocket on the crank will be at 12:00 but the timing mark on the intermediate sprocket may not be opposite it. This is not a problem so ignore it. It would probably be best to remove the rear cam cover so as to view the cam sprocket timing marks on the rear bank cams also to verify the timing. If you have the crank at #1 TDC and #1 is at TDC firing then the timing marks on the cam sprockets will be at 12:00 RELATIVE TO THE CAM COVER MOUNTING SURFACE....or 45 degrees from vertical. You will need to turn the intake cam and exhaust cam on the left hand cylinder head so that the timing marks are at 12:00 relative to the cam cover mounting surface. Be sure the sprockets are installed correctly so that the LI slot and mark are on the timing pin for the intake cam and the LE slot is on the timing pin for the exhaust cam. If so, and the appropriate marks are at 12:00 then you are ready to install the chain.

Remove the cam chain tensioner on the chain guide on the left side of the engine to gain enough slack to install the chain. You need to unbolt it anyway to reset the plunger to the shortest length before reinstalling it. Leave it off until the chain is back in place, bolt the tensioner in place and allow the tensioner to extend and it will automatically set the tension.

You will have to remove the bolt holding the cam sprocket on to slide the sprocket off the cam to engage the cam. Get the chain over the intermediate sprocket, then the exhaust cam sprocket and then the intake cam sprocket.

Be very carefull turning the engine over. Take all the plugs out and turn the crank carefully feeling for any resistence at all. The pistons can easily hit valves that are open and bend them. Since you have the head on and the cams are not timed on the left side and not turning then this is a distinct possibility if you are not carefull. Similarily, turn the cams carefully on the left side also least you drive a valve into a piston that is at TDC. If you can turn the cams to the TDC position (marks on the sprockets at 12:00) then that will give you the best chance of not hitting anything when you then turn the engine over. If you feel any resistence don't force it. Take all the plugs out so the engine turns easily and check the position of the pistons on the left side by sticking a wooden dowel down the spark plug hole to make sure that none of the pistons are at TDC when you are trying to turn the cams. If a piston happens to be at TDC and you turn the cam there is a distinct possibility of hitting a valve against a piston.

The correct procedure that makes this easy is to have the engine at TDC before dissassembly so that it doesn't need to be turned and then time the cams on the head before installing it. That way there is no chance of bending anything but that is not where you are at.

Absolute worst case is that you had the cams in such a position that a valve WAS open when the head was installed AND that piston happens to be near TDC. If that was the case you will have already bent some valves. Hope this is not the case but it has happened when a head is bolted on an engine that is in an unknown position. If you check the piston position with the dowel (or looking down the spark plug hole) and none of the left side pistons are near TDC then this is unlikely to have happened.

You will need to properly tension the harmonic damper when reinstalling it. Do NOT use an impact to install the damper. Do NOT hammer on the damper to install it. Pull it on with a damper puller or a piece of threaded rod and a nut and stack of washers. The damper is a tight press fit and is hard to pull on. It MUST be pulled on correctly or it can be damaged. The bolt must be tightened correctly or the oil pump will not turn when the engine starts. It takes about 250-300 ft lbs to reach the correct torque and angle spec so you will have to lock the crank down at the flex plate or somehow to hold it to tighten it correctly.

07-18-05, 10:19 AM
WOW, I opened a can of worms,
I'm fairly sure that all the valves were closed when I installed the head, the cam's lobes were all to the sides and the lifters were up.

three of the pistons are nowhere near TDC, but the #4 piston is about 1/4" from the top, I slowly turned the cams, 1st the exhaust cam, there seem to be no restriction, I turned the intake cam and it seemed fine until the lobes started opening the #8 intake valves, it seems to be stuck, the cam will not turn, (I'm trying to be easy with it, not forcing it), it may be nothing, it could be just the valve spring tension, (the piston is at least 2 to 3" down from the head).

Thanks for typing all this info in here.
Maybe I will be able to return the favor someday.


07-18-05, 01:15 PM
Make sure that all the valves on the left hand head are as close to closed as possible before you turn the crank to find #1 TDC firing. The right head should be fine as you still have the chain and such on it and it was never dissassembled. Get the engine to TDC #1 and then gently turn the cams into position on the left head monitoring piston piston and which valves are opening. You can turn the cams either way to get them in time so sometimes it will work to turn the cam backwards to avoid opening a valve unnecessarily.

When you have the tensioner off you will see a little chain link looking device or lever on the side. If you wiggle and move the little lever it will disengage the rachet in the tensioner and allow you to depress the tensioner plunger. Depress it fully and move the little lever back into position so as to hole the plunger in the locked position. If you stick a golf tee into the open hole in the little lever it will hold the lever in the locked position and keep the plunger from extending as you install it. Just get it into place and torqued down with the chain in place and pull the golf tee out like a grenade pin. That is how it is done in the factory....no one has any shortage of golf tees.....LOL.