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Old 01-05-2018, 04:24 PM
bender-offender bender-offender is offline
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2007 Xterra
 
Join Date: Feb 2017
Posts: 8
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Quote:
Originally Posted by geo6x View Post
I'm a late bloomer and i guess so is the VQ40 in my Xterra....i'm just doing the timing chains now. Motocopter mentioned that his right bank cam jumped when he removed the secondary chains. I'm at this point in the repair now. I want to avoid removing the valve covers if possible. My question is...IF either of my cams jump, is there an "easy" way to recover without all the added work of removing the intake and valve covers? I noticed in one of his updates, it sounds like he had a buddy help get his timing recovered without removing valve covers. And Ditto to all who have contributed here....this is a great thread! Should be required reading for all of us Nissan do-it-yourselfers!
I had something similar happen to me so here’s my experience:
If the exhaust cam was the only one that moved, you may be able to just turn it back to where it should line up with the chain markers. However, if the intake cam moved, you’ll need to do a little more work. I’m not 100% sure if this is accurate, but a mechanic buddy from my church said the intake cam needs to be rotated in the same direction as it naturally rotates (I believe clockwise) until you get it back to the correct postition. In other words, you can’t rotate the intake cam backwards or it could mess up the variable valve timing.

That being said (IMPORTANT), before you rotate ANY cams, you need to make sure no piston on that side of the engine is up otherwise turning the cams will bend your valves. So, since there’s six cylinders, and it takes one 360 degree rotatation for all the cyclinders to fire, that means every 60 degrees a cylinder is all the way up. So what I did was rotate the crankshaft WITHOUT the primary chain on 30 degrees so that NO cylinder was up. Then I rotated the intake cam in the correct direction until it was lined up. Once the intake and exhaust cams were good and the secondary chain was back on, I rotated the crankshaft BACKWARDS 30 degrees to TDC.

Now, what I said could be way wrong in how this can/should be done, but it worked for me and my engine has been running great since. So you may want to double check with others.

Concerning the valve covers, they aren’t too difficult to remove. It can be a pain to get to some bolts, but it’s better to be very certain all your cams look correct before you put everything back together incorrectly and then crank the engine and bend some valves. Good luck with the fix!
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