Hi all,

I'm rebuilding the 4.0 from my 2000 XJ and I got the shortblock all together, put the timing cover and oil pan on. When I put the timing sprockets and chain on, I made sure the marks pointed at each other. But I wasn't paying attention and now I think the cam is 180 degrees out.

Correct me if I'm wrong, but when the timing marks point at each other, the #1 piston should be at TDC and both valves should be closed? Right now with #1 at TDC the exhaust valve is open.

 

Timing marks and dist timing two different things. This....http://www.angelfire.com/my/fan/dist_index.html

 

You're at #6 TDC compression. Turn the crankshaft damper 360* to get #1 at TDC compression. Check sprocket alignment again.

 

CCKen that's what I thought. Both valves are closed on #6. If I rotate 360 degrees and #1 is up top, both valves closed I should be good right? Or do I have to pull the timing cover

 

It should be okay.

 

Ok cool, I just rotated it 360 and now #1 is at TDC with both valves closed. I don't have the crank pulley on to verify its pointed at 0 but the keyway is pointing straight up. I think I'm good to go.

 

Keyway pointing straight up is about right.

 

I still think it's off. Everything lines up, but when you go to rotate it off of TDC, the intake valve starts to open. It it was truly on the compression stroke the intake would have already opened and closed.

I'm going to try taking the chain off, rotating it one time and putting the chain back on and seeing what happens. Its intake, compression, power, and then exhaust. So with it at TDC the intake shouldn't open when you start rotating it.

 

Are you sure it's the intake lifter that's moving?

 

Yes, when I have the marks lined up and both valves closed on #1, as soon as I start rotating it further I can watch the intake lifter start to compress the valve spring (I put the head on now).

I just tried taking the chain off when I get to what I think is the compression stroke, and the cam is indeed 180 degrees off. So I rotated just the cam until it lined up with the crank again, put the chain back up, and got the same result. So maybe that's how its supposed to be?

 

Maybe I'm overthinking this... the cam only rotates once for every two rotations of the crank. So if the marks are lined up, that's the only position I think the cam can be in.

I have another 4.0 sitting around still together and I pulled the timing cover off and rotated it, same thing. As soon as you rotate past TDC with both valves closed the intake valve starts to open. So I guess it's normal.