M20 Timing Belt help needed!

[aznbo187]

Hey guys, I'm in the middle of a timing belt change with my friend (m20 motor).

I'm a bit lost or may have screwed up on a part.

So we are at the part where we are ready to install everything, and making sure the camshaft and crankshaft sprockets are aligned. They were initially when we were taking it apart, but nothing having the belt tensioned enough and rotating it made the timing marks not match.

We adjusted the belt until the camshaft sprocket lined up. Then took of the tensioner and removed the belt from the camshaft sprocket. With the crank sprocket being independent from the cam sprocket, we then rotated the crack sprocket, but halfway through, it would not let us rotate it anymore. We didn't go any further and that's where we are now.

I think the pistons hit the valves, thus the resistance. Also, reading further, I believe we should have left the belt on and rotated the crank until the crank sprocket lined up, and then adjusted the cam sprocket instead of the crank sprocket. Both sprockets we only adjuster clockwise facing the front of the engine.

Please advice us on what to do at this point. Can we adjust the crank sprocket counterclockwise, until it lines up wit the O|T mark, and then adjust the cam sprocket?

Thanks!

[PeaveyBassist]

You should have left the belt on, rotated till the crank was at TDC and double checked the cam. Never take the belt off until you confirm twice that both sprockets are correctly lined up. If the crank wont turn, dont put much pressure on it because you could bend a valve. Turn the crank back to about where it was before. Put the belt back on and tension it. Rotate motor VERY slowly (make sure no resistance) until you get both cam and crank to TDC marks. If its not perfect, Line up the cam, take the belt off and then rotate crank to correct spot. Be VERY careful moving them independant of one another. You dont want to bend a valve and have to pull the head off.

[catchuk]

also if you remove the spark plugs the resistance should be less to make it easier to feel if the valves are hitting.

[aznbo187]

Initially, before removing the original belt we checked to make sure it was lined up. I'm not sure how the timing changed in between there, but here we are now.

We turned the crank back to about where it was, put the belt on but the crank sprocket is about an inch of, when the Cam sprocket is at the correct location.

I have no idea how cams/cranks correlate to each other, but the goal is to have the cam line up while the crank lines up with each of their marks.

If I read your instruction correct, even if they are now not lined up correct, while tensioned, I should turn the crank and they will eventually even out and have matching timing? I thought that with each revolution, they just land back on the same position when rotated 360 degrees.

Thanks for the advice so far. Please clarify a bit, thanks.

[nando]

an inch off will mean they will hit. you won't be able to turn it. why not just turn the crank back an inch and put it together? the only real relationship is both the cam and crank need to be at TDC. if moving the crank backwards will do that, you're fine.

you have to move the crank 720 degrees for one 360 degree rotation of the cam, as it turns at half speed. it doesn't matter though if you only turned the crank 360 degrees while leaving the cam in one place (if you could), as long as both marks are at TDC when you start the car it will work.

[PeaveyBassist]

Yes when you rotate it, it will put them at the exact spot they were, however somehow they arent in sync any more. When you move the crank back to where it was and put the belt back on, you can now rotate the engine without any piston-valve contact and get them closer to the position they need to be in. It wont make them line up by doing that but it will get them in a position where you can then take the belt back off and rotate both in minimal increments to get them to both line up. Post up some pics of the position of the cam/crank. That might be able to help us help you more.

[lennon]

you misread his post. if they arent lining up, youll need to move one independent of the other. line up the cam and then move crank accordingly, but be careful not to smash the valves.

edit- well there you go OP! more helpful posts

as long as both marks are at TDC when you start the car it will work.

that^ pretty much sums it up

[calz4m]

I don't understand why you rotated the crank once you took the old timing belt off. Once you have it a TDC with the belt on there, you just take the tension off and remove the belt. From there replace the tensioner and put on new belt. There is NEVER a need to move the crank/cam sprocket independently of each other. Go back the way you came with the crank, as we suggested by other posters. Do it slowly and carefully. I would remove the plugs to be safe. Even if you are off by one tooth on the cam sprocket when you put it together the timing will be advanced and it will not run as well as it should. Good luck and just be slow and deliberate. I doubt highly you have done any damage to the top end.