I'm a dummy and rotated the Cam shaft independent of the Crank shaft

suspension
nissan

#1

So, I’ve got a good ol 1987 Nissan Pickup - 4 cylinder 2.4 liter - Z24 engine. First time ever getting so far into an engine btw. During a head gasket job I, in my inexperience, allowed the timing chain to slip off the crank shaft. This required taking the front cover off and re installing the timing chain. Again, in my inexperience, I moved the cam shaft around while the timing chain was not installed. At this point I realize the error of my ways. That being said, is there any way to put the cam shaft back into the exact right position? Possibly something to do with aligned the valves in a certain way. This IS an interference engine. This truck is my buddy and I’d like to get her working again. Thanks.


#2

If you’re doing a head gasket job, I hope you have some sort of manual. Each engine has it’s own set of particulars when refitting the cylinder head and a manual is invaluable. The same manual should have the proper timing chain alignment instructions.

You can also find step-by-step instructions at www.Autozone.com, setting up an account, and using their repair guides. I just checked, and your '87 2.4L Z24 engine timing chain procedure is in there. It is slightly involved, so I don’t want to try and retype them here and make a mistake. Just be careful, because the L-series engines use a different method.

And, BTW, don’t feel bad. Rotating the camshaft on an OHC engine is easy to do when your pulling the head. And even just changing the chain.


#3

If the crankshaft is turned to put the timing mark 90* before top dead center, all 4 pistons will be half way down their bores and you can spin the camshaft with no chance of a piston/valve collision. You need a good manual. The proper way to handle removing the head involves using a foot long piece of firring strip to wedge the chain in its guides before loosening the camshaft gear.


#4

You’ll just have to re-time the engine is all. Which means to align the crank timing marks and the cam timing marks to spec, then re-install the timing chain. Before moving the cam or crank, find a copy of the manufacturer’s procedure on how to do this without banging the valves into the piston or the valves into the valves. The method varies engine to engine. If there’s any question at all whether the timing marks are correctly aligned, seek someone with experience to double check before starting the engine. btw, Make sure when you do all this the spark plugs are removed. That makes it easier when hand turning the engine to notice a valve/piston or valve/valve interference.

Edit: If you have any doubt where the pistons are, up, down, or midway, you can always poke a wood dowel down the spark plug holes.

There’s an ignition component to this too which may offer some add’l confusion, depending on how the ignition system works in your car. Crank TDC is ambiguous, as it occurs at the top of the compression stroke, and the top of the exhaust stroke. You want the ignition to be timed to fire at the top of the compression stroke. The shop manual should explain how to insure you are sync’d to the correct phase.


#5

There should be index marks on the crank and cam sprockets, and the proper procedure for orienting them will be in any service manual.


#6

What about the chain tensioner? There is a special tool used to keep the tensioner depressed whenver the head is removed or the chain is removed up top.
If the tensioner pops out the front cover has to come off.

Lacking the official tensioner tool, a substitute could be made out of a wedge shaped block of wood and a pull cord; with the cord used to remove the wedge after everything is timed and bolted up.


#7

U set timing with #1 cyl at tdc so rotating cam independently of crank at tdc is not good. Valves open when piston is at tdc. Not A good practice. U ensure cam sprockets are in proper orientation prior to bolting head onto block.