Thread: Timing Madness. Cam timing = Good. Base timing = Not Good?!? (A Mystery)

Dowel pins. We rotated the motor by hand quite a bit to check that the cams were working correctly. During all of that we were re-checking cam timing. Everything seemed to line up. The valve cover was installed and removed about 3 times during all of this to re-check stuff.



Ya, and if that was even the case why would that affect my timing so much? When we took the tensioner out it seemed to have good push. Had to use a vice to get the hook back on.

I could try a different tensioner, but I'd want to know why a bad tensioner would cause timing to be off so much?

Thanks!
-G

Well, since the tensioner is hydraulic, if it fails, it doesn't keep the chain tight as it should be, and it will allow slack to effect timing a bit. The amount of slack that is maintained by the tensioner could throw your mechanical timing off as much as 5 degrees, if not a bit more. It wouldn't be a constant issue, though. Remember that the crank "pulls" the chain in a clockwise rotation, and the chain should be super tight between the exhaust cam gear and crank pulley. If there's slop, then the exhaust and intake cams can still "walk" a bit, if not completely jump teeth before the crank pulls the chain tight again. If you've noticed, when the cam is rotated by hand it has hard spots, and really soft spots that will alow it to jump pretty easily during the cam's duration events.

Anyhow, I have never personally seen a chain stretch.

Others are pointing to the head/block being decked, which is also a likely scenario. It's a possibility, that's for sure. The only downside? You will need to remove the head to see if it's been decked before, since you can't really get a precise measurement with the head on the block.

The OEM rebuild/gasket kits I've seen come with red rtv. If there's red rtv on the timing cover and oil pans its a sign that the motor has been torn down before. I've seen a few jdm engines like that.

Like Cliff said that doesn't tell you for sure but your issues are symptomatic and there's only so many things that can cause what you are describing.

No red RTV on lower or upper oil pan. We changed the rod bearings when we got the engine. Still doesn't necessarily rule out some engine work though.

Did the head look SUPER clean when you removed the valvecover? As in no staining of the aluminum from oil?

If it's not a tarnished color or gold or something, chances are the head was removed, decked, and pressure washed.

Easy way to tell, is to compare how the motor looked when you did your bearing job, to how the head looked. If they were two different colors/shades, you know what happened.

There's always little hints if you look at them carefully. SR motors are freaks though where one that looks sludged up and beat down will run like a raped ape and one that looks factory fresh will instantly throw a rod bearing or put out low power even with a perfect install.

if i were to guess i woul pull it back apart get a new chain and aftermarket tensioner as said before retime everything and ill put my bottom dollor on it that it will be fixed i can get a chain for about 30$ (brand new) from nissan my cousin works there and hooks me up