280z L28 setting engine timing

[Zed Head]

22 minutes ago, Patcon said:

 I guess I wouldn't want to end up a link or two off. Might not destroy anything but might not make good power either. It seems like the only way to know for sure at that point is to remove the front cover

That's what the marks on the engine parts are for.  Notches, grooves, pointers, to verify correct cam timing.  If you go slow you can turn the engine by hand once it's together.  If you're really strong you could probably bend a valve by hand, but you'd have to have hands of stone to not feel the initial contact.  Odds are he'll get it right the first time.  I think I did some math once and found that one chain link is like 7 degrees or something like that.

If he takes the front cover off he could end up on a whole trail of "while there" fixes and replacements.  Front seal, water pump, timing chain is probably worn, probably break some thermostat housing bolts so better have the drill and Helicoil ready.  Don't damage the damper rubber while pulling the damper...

Many possibilities.  Kind of comes down to risk/reward.

[Zed Head]

2 minutes ago, madkaw said:

Why do more guessing than he needs to.

The tensioner popping out.  "Need" is subjective.

He probably hasn't been back yet because he realized the tensioner popped out three weeks ago.

[madkaw]

Looks like the tool is in there

[madkaw]

4 minutes ago, Zed Head said:

That's what the marks on the engine parts are for.  Notches, grooves, pointers, to verify correct cam timing.  If you go slow you can turn the engine by hand once it's together.  If you're really strong you could probably bend a valve by hand, but you'd have to have hands of stone to not feel the initial contact.  Odds are he'll get it right the first time.  I think I did some math once and found that one chain link is like 7 degrees or something like that.

If he takes the front cover off he could end up on a whole trail of "while there" fixes and replacements.  Front seal, water pump, timing chain is probably worn, probably break some thermostat housing bolts so better have the drill and Helicoil ready.  Don't damage the damper rubber while pulling the damper...

Many possibilities.  Kind of comes down to risk/reward.

I believe one tooth is 9 degrees

[Zed Head]

In the end it boils down to comfort level.  I made a tiny paper protactor once to measure an angle on small small part.  Just took a short time with paper, pen and a big protractor.  If that was my engine I'd probably do that.  I trust the angles and would be comfortable putting everything back together that way.

Some of the forum people could probably design and build a chain tool that allows the chain to slide by so the tensioner pop-out problem doesn't exist.  I saw on another forum that some guys built a little jig to hold the sprocket where it would be on the head and mounted the sprocket on it on top of the block to hold the chain tight.  Probably doable with some wood.  If the common wood or plastic tensioner is tight the chain will ball up underneath it when you turn the crankshaft.

And as we all know, the more bolts you remove on these high mile engines the more bolts you'll break.  

Anyway, good luck to him whatever he decides to do.

Here's another one - remove all of the rocker arms so that the valves are all closed.  Put it together, turn it to wherever it needs to be to see the marks.  Adjust, then reinstall rocker arms.

[Patcon]

Does the crankshaft bright link end up in the same place every time the engine turns? I was under the impression that the bright links didn't line up on every revolution. I understand getting it to TDC that's easy enough with some measuring tools. Just trying to figure out how you can be sure which link is supposed to go on the cam gear. I never could find the stretch test marks on the head we just installed. I looked and looked and could never find them. I had to rely on the bright links to set it properly. I am not sure the camshaft gear was the OEM one though.

[madkaw]

37 minutes ago, Patcon said:

Does the crankshaft bright link end up in the same place every time the engine turns? I was under the impression that the bright links didn't line up on every revolution. I understand getting it to TDC that's easy enough with some measuring tools. Just trying to figure out how you can be sure which link is supposed to go on the cam gear. I never could find the stretch test marks on the head we just installed. I looked and looked and could never find them. I had to rely on the bright links to set it properly. I am not sure the camshaft gear was the OEM one though.

Probably wasn’t an OEM sprocket . I believe it’s every fourth revolution the links end up correctly. 

[fairladyz432]

so just to be absolutely sure, I should only be turning the crank when the head is on right? Or the other option is Leaving the head off makes it a bit easier to hold down the chain tension tool while cranking the engine to zero mark. As soon as the crank pulley is lined up to zero mark I can install the head on and then install the chain onto the cam sprocket and then remove chain tension tool. Does that sound right? Seems like the easier way, also the head is in correct position currently. I attached a pic of the head. 

[240260280]

Cylinder #1 looks close enough to TDC in top picture above.

Here are steps:

1. Install sealant at junction of block and timing cover

2. Ensure valve alignment matches head is at TDC.

3. Install head gasket and head.

4. Torque head bolts correctly.

5. Remove cam sprocket.

6. Fit chain on cam sprocket

7. Install cam sprocket (don't torque cam nose bolt yet)

8. verify timing marks on crack pulley and on cam sprocket.

9. If timing marks are off a little: Turn cam a little so that the crank pulley timing mark is aligned then note how many teeth the cam sprocket is off.

10. Remove cam sprocket and adjust to match the correct teeth.

11. repeat 6 to 10 until aligned. (You can use sprocket settings 1,2,or 3 to optimize cam advance).

12. Torque cam sprocket

13. Remove timing chain tensioner tool.

 

[fairladyz432]

thanks for the help. will report back