Hi: I have a 1998 S90 (6 cyl). B6304 engine. I'm rebuilding the top half of the engine after the guide bearing for the timing belt failed. I have been working on and off for almost a year.

I’m getting close to being done.

I’m installing the timing belt and CAM gears and trying to get the alignment correct between the 2 cam gears.

From earlier posts and my research, there are 9 possibilities (3 x3 = 9) on how the relationship of these cam gears can be with each other. Each cam gear can be installed in 3 positions.

The alignment of the crank gear to the block is not a problem. I always keep that aligned with the mark on the lower block.

My understanding is that only 1 out these 9 cam possibilities will result in full clearance between the valves and pistons once the crank is rotated 2 full revolutions.

I’m not sure this is correct.

In my set-up of the nine possibilities, I have found 3 conditions in this setup where I can get full clearance as I rotate the cranks the 2 revolutions.

So this is my dilemma.

Of the 3 remaining possibilities which one is correct?

I have tried looking into the intake and exhaust ports to view the valves to see if they are opened or closed. But it’s hard to tell.

I have even gone as far as to put compressed air into the spark plug hole so I can feel if air is leaking out the intake and exhaust ports to help determine if certain valves are open or closed.

I have pages of written observations on what the results were when I put compressed air into each cylinder. Sometimes air leaked out the exhaust ports, sometimes the intake port, sometimes both, and sometimes the crank would rotate (clockwise and counter-clockwise) as the compressed air pushed the piston down.

I have spent day’s on this. I know this set up can be done correctly without using the expensive “cam alignment tool” from Volvo. I have the Volvo manual and this alignment tool really doesn’t look like much.

I think I’m working to hard on this. But I’m close.

I have a few questions:

1. Is there any relationship between the machined slots on the back end of the cams to the correct alignment of the cam gears? I still can see the ends of the cams because I haven’t install the pick-up sensor or seals yet in the back.

2. When the crank gear is set to it’s alignment mark, what does this represent? My observations show that this is NOT the TDC (top dead center) of cylinder # 1. Actually cylinders 3 and 4 are just about at TDC at this mark (maybe 10 degrees prior).

I’m sort of at my wits end on this. Can anyone offer any assistance? Help? My hair is almost gone.

Thanks in advance ....Mr. Tool.