Don Carter

So I made a bit of a mistake last night and removed the timing belt on my TBF car replacement engine without lining everything up to 45 BTDC. The crank is currently about 180 degrees off from 45. I have the 45 marks on the cam gears, but I need to verify that it's ok to gently rotate the crank to 45 BTDC before rotating the cams to the 45 marks.

I understand that it's safe to rotate the cams when crank is at 45 BTDC, but at what cam position is it safe to rotate the crank? Does the spring loading of the valves cause the cams to naturally land at safe positions where the valves are closed?

I'd prefer not to removed the valve covers again, but I guess that might be the best way to see when the valves are closed.

Lizard928

Remove the plugs,
SLOWLY rotate the crank, if it feels like it hits ANYTHING stop and back it up 5deg,
then rotate both of the cams roughly half a turn,
again rotate crankshaft slowly,
repeat until at 45 or TDC.

I do all my belt jobs at TDC btw.

Landseer

That will work if plugs are out especially (easier to rotate)

But wait. Another way.

If you removed the belt and neither crank nor cams moved.... put it back on right where things are.

Using a string or tape measure, you can verify that the cams gears are in the right place relative to each other by measuring the distance each needs to travel clockwise to reach the TDC mark -- from where they currently are located. If the same distance, that pretty much verifies that one didn't spring while you slept!.

Not desired, but the timing belt can be changed anywhere the engine comes to rest. The question is whether one or the other cam will spring forward or back at that location after belt is removed.

Bill Ball

If things have not moved (much), the cam gears should be about 90 degrees or 12 cam gear teeth from TDC. If close to that, line up the cam gears at 12 teeth from TDC and slip the belt back on.

blown 87

You can always take the cams out and turn the crank to 45 and then put the cams back in.

76FJ55

HERE is another thread on the same problem. you can read through it an see if it helps.

WallyP

Another vote for just slipping the belt back on.

76FJ55

I agree the easiest solution is to figure out where your at and get the cams as close as possible and reinstall a belt. The with all the plugs removed turn slowly to the 45 mark.

Don Carter

The passenger side cam did move when the belt was removed, so I didn't feel comfortable just putting the belt back on, but it's a good point that even if it's a tooth or two off, it may be a safe way to rotate the crank to 45.

Simon,

Thanks for the link, that is exactly the type of thread I was looking for, but definately not a happy ending.

This thread confirmed some of what I thought, but wasn't sure about. Mainly, with the plugs out (they are), and gentle slow turning, I'm probably not going to do any damage turning the crank. Something I didn't realize is that the only reason not to turn the crank counter clockwise is that the belt could slip a tooth, but since the belt off, I can go counter clockwise.

Also interesting the varying views expressed in the thread.

I feel pretty comfortable with the situation now, and will take another look this evening. I know I haven't damaged anything yet, just trying to be very careful with my new $3k motor. Should be no problem getting the crank to 45, then positioning the cams to the 45 marks already on the cam gears.

Thanks for all the help, and I'll follow up when I get everything back together.

Don Carter

I was able to gently turn the crank by hand (no tools, just using the damper) to 45 with no obstructions. Then I rotated the cams to the 45 marks, all very easy, now ready for the new belt. I was probably more worried than I needed to be, but this is my first TB experience and didn't want to re-align without fully understanding it.

Thanks for all the advice. Hope to be reinstalling the engine soon, possibly even tomorrow.