I done cocked up...

[Junk_30]

So Im in the middle of a timing belt and water pump replacement and my dumba** thought it'd be a good idea to take the belt off the cam gear before I moved the engine to TDC and while removing the harmonic balance the crank was moved slightly, does anyone have any suggestions on how to get the engine back to TDC without bending any valves

[amcp]

Take the head off.

[95BMWIC]

So Im in the middle of a timing belt and water pump replacement and my dumba** thought it'd be a good idea to take the belt off the cam gear before I moved the engine to TDC and while removing the harmonic balance the crank was moved slightly, does anyone have any suggestions on how to get the engine back to TDC without bending any valves

The correct approach would be to remove the head and then set crank to TDC and the head to TDC and re-assemble. This is the only way to ensure it would be correct.

You could try to move the crank back to the position you thought it was and then put belt back on - then turn the crank a few times (with belt on) to see (or listen) if there is anything hitting. This is a riskier approach as you might not necessarily hear (or sense) the valves nicking the pistons - unless you are way off. The only way to ensure it is correct is option #1 above.

Plus side - if you take head off - it is perfect time to inspect head at machine shop - replace springs and valve guides and double check bottom end.

[E30SPDFRK]

Where are the timing marks now? you might be able to spin the crank to a safe position where all cylinders are down, spin the cam to TDC, then move the crank back.

[95BMWIC]

Where are the timing marks now? you might be able to spin the crank to a safe position where all cylinders are down, spin the cam to TDC, then move the crank back.

Your answer sounds intriguing..

Question Byron..

As I am thinking through this - Isn't the ratio for the Cam to Crank - 2 to 1? Maybe it doesn't matter as the rotation ends up in the same place each time (intake vs exhaust valve position) - I'm wondering about Motronic and firing order - Maybe this is a moot point.

If the crank is in a position that all pistons are down - and you then set cam to TDC. Can you move the crank to TDC without hitting valves? Pistons one and six are up in TDC - so valves for 1 in 6 are the correct location on the head so not to be damaged. But 3, 4, and 5 are not - is one of those in the open position (whereas spinning the crank would cause 3,4 or 5 to hit the valve)?

[Northern]

if "slightly" means only a tooth or two, throw the belt back on and rotate the whole thing until it's at TDC, then adjust. Just take the plugs out and go gently. Stop if you feel resistance.

[Junk_30]

Im currently at school so I only had time to pull the spark plugs during lunch, So the Crankshaft has about 20 degrees of motion and the the closest It comes to the TDC notch is about 2.5mm away. This is while the belt is off the cam gear, the cam gear tooth with the mark is about 30 degrees from the notch on the head. My auto tech teacher told me that unless I gave it an immense amount of force very suddenly I wont bend the valves while turning the motor over by hand. The problem now is figuring out what angle I need the crank to be at in order to move the cams. Ill try and take the valve cover off during this period to see whats up but if I run out of time itll have till tomorrow morning

[bmwman91]

Pull a spark plug and stick a dowel down the bore so that it rests on the piston crown. Carefully rotate the crank with a wrench on the damper bolt and make marks on the dowel as you see it stop and reverse direction. You should be able to get VERY close to TDC like this, and certainly more than close enough to avoid interference with valves. Alternatively, if you have a large caliper, you can use the depth gauge instead of the dowel and watch the readings to see where TDC is as the piston moves. Or maybe tape a dowel onto the depth gauge to get the necessary reach.

I have done things like this in a pinch and had no issues.

As far as bending valves, the only way you would have done that is if the valves were being used to "constrain" the crank as you broke the damper bolt free, which I assume you did not do. If the crank moved ~20 degrees while you were setting up and just turning it by hand, then you are fine.

[vtechnik]

First take all the spark plugs out so you know any resistance you feel isn't coming from compression. Also I believe there have been cases on here where people have bent their valves by turning the motor over by hand so be extra careful. Next, like said above, put a belt on it and rotate it slowly back to where the crank is at tdc. Then adjust the cam to tdc.

[E30SPDFRK]

Im currently at school so I only had time to pull the spark plugs during lunch, So the Crankshaft has about 20 degrees of motion and the the closest It comes to the TDC notch is about 2.5mm away. This is while the belt is off the cam gear, the cam gear tooth with the mark is about 30 degrees from the notch on the head. My auto tech teacher told me that unless I gave it an immense amount of force very suddenly I wont bend the valves while turning the motor over by hand. The problem now is figuring out what angle I need the crank to be at in order to move the cams. Ill try and take the valve cover off during this period to see whats up but if I run out of time itll have till tomorrow morning

Post a picture of the cam gear and the crank pulley when you get home.

[Junk_30]

Im using a desk top rn so I cant post any pictures, Back at school rn and my friend is bringing his bore scope, the camera thingy.

[Junk_30]

Got the valve cover off the take a look at where the valves are positioned ill try and post some pictures during my study hall period

[superj]

Move the rockers over so all valves are closed and than align all the marks. Then you can out the rockers back and set the valves

[noid]

Move the rockers over so all valves are closed and than align all the marks. Then you can out the rockers back and set the valves

+1, move the rockers off the valve stems, which will keep all your valves closed.

Then adjust to TDC.

[AndrewBird]

There is no position where at least 1 valve isn't open.

Use the dowel trick to move the pistons all down equal to each other. BBQ skewers would work. Just make them all the same length, stick on in each spark plug hole and turn the crank until the tops of all of them line up. Then rotate the cam gear until the marks line up, then finally rotate the crank until it lines up.