Is there enough slack in the timing chain to re-position the head?

[thehackmechanic]

I'm advising Eric King and his daughter Sarah, who are doing a 2002 project together. Their 2002 appears to have jumped teeth on the cam sprocket. 

 

Side-stepping the issue of WHY it jumped teeth for a moment (and I'll grant that it's a big issue), if the spring is removed from the timing chain tensioner, does that create enough slack in the chain to be able to lift it off the cam gear and re-position the head to top dead center, or does the front timing cover have to come off to take off the cam gear?

 

--Rob

 

[King+Sons]

(background on our specific situation here, for those who want it)

[Oldtimerfahrer]

Hi,

I would think not...as in take the cover off and examine the tensioner, chain and sprockets. If you can find the masterlink, split the chain and insert coathangers to hold it up I.e. not let it fall in the sump. If it has slipped, now is the time to check on the cause (stretched chain or improper setup and get the timing dead on). You don't reposition the head, you rotate the crank and set the valve timing with the camshaft and then reattach the chain. If you're not sure, get a timing wheel to actually measure whether the markings are producing the right results. No guessing or close enough, this is hard science and measurable. The factory marks are good enough for a stock engine, but if they don't line up there is an issue. I had a mismatched head (wrong piston and head type) so there was contact and timing chains were not the issue but that is an exotic and dumb problem created by the PO.

Regards,

Andrew

[HBChris]

I did this yesterday, my son's 2002A was off one tooth (retarded).  No wonder I couldn't get it time properly!  The tensioner was stuck in its housing and provided no tension.  I simply kept the Flywheel on TDC, removed the upper timing cover, removed the piston tensioner, removed the gear and kept it tight in my hands, turned the cam forward with a vise grip on its nose until the mark on the cam was also TDC.  I then picked up one link and moved it on the gear.  Guess what?  The four bolts lined up perfectly with the gear.  I bought a new tensioner piston but it still wouldn't move smoothly so I used a small half round file until the interior of the piston housing allowed it to move freely.  Much easier than I thought too!

Edited April 5, 2017 by HBChris

[Preyupy]

If there is enough slack in the chain to "jump a tooth" then you have some major work to do.  The only way this can happen is if the cylinder head has been excessively surfaced AND the chain has stretched A LOT.  If the cam timing is off it's because the last person that had it apart put it together wrong!   The only way to retime the cam is to do like HBChris said and remove the valve cover and upper timing cover, remove the cam gear and retime it correctly. 

[Buckeye]

+2 what Preyupy and HBChris said

[oldguy]

Last time I head a head do this.  There were bent valves.  Perform a leakdown.  If no bent valves then you do this.  Remove valve cover and front cover.  Mark cam gear to chain in one spot.  Remove tensioner.  Unbolt cam gear making sure not to drop cam gear into front cover or loosing tension on chain to bottom gear.  Use the paint mark as a reference to move it the one tooth.  Put the 4 bolts back in.  Rotate engine with upper front cover off to verify that timing is correct. 

[HBChris]

The key is a functioning tensioner, mine was not.  It was very easy to do as well.