cam/timing chain help needed

[Structure240sx]

first how much do the cam sprokets get torqued? its not in my fsm.

now the problem im having. i took my cams out a couple weeks ago to do a leakdown test on my engine. results were good so thats a plus. well i jsut got time to go put it back together today. i got the cams in with all the brackets torqued in jsut like it says in the fsm. i lined up the timing marks and links. on my chain i see 1 silver link and 2 dark links. i lined up the silver with the mark on the idler sprocket and the 2 dark ones on the cam sprockets. this was done with #1 at TDC. i get the chain on and all and start to turn it over to makes sure everything is ok. well turning it over half the time doesnt take much then the other half takes a bit more muscle. in that time the chain on top will go from being loose to nice and tight. after a couple times i look back at the chain and the links are one link off their mark. in one rotation ill hear one click i think it might have been fromt he cam sprocket not being tightened as much as it should have.

so i need to know what im doin wrong. why does the cahin go from being tight to loose? before i took it apart i did have the timing chain clickin everyone talks about. think it could jsut be that? would just a new tensioner fix it?

sorry its so long but i wanted to get any details out that i could. thanks for any help i just hope i didnt bend any valves

[jrc90240sx]

Have you ever replaced your timing chain? I just rebuilt my engine, all new parts, and i had a very bad rattling nose. only to find i have alot of slack in my chain. i am know replacing all the components of the timeing chain, but belive the tensioner to be the case of the problem. also how do your guides look?

[Structure240sx]

guides have some nice grooves in them. but why isnt there always slack.

is there a possibility that i switched cams? intake on exhuast side and exhuast on intake side. i know one has a green stripe and one has a yellow. i put the yellow as the intake i think, the car isnt here. im goin to feel real dumb if i messed that up

[jrc90240sx]

Well i had alot of slack, almost enough to pull the chain out and move it up a link. and i already have nice groves in my guides, and my car has only been running for 1 month. something you could try. pull the valve cover, see if there is slack, and what side its on. if its on the exhaust port side, put your car into 1st and rock it forward so it puts some force on the crank, now check to see if your chain has the corect tension, or if the exhaust side is nice and tight, and the intake side has slack, if so i would say you need a new tensioner

[DAEDALUS]

If you switched the camshafts you would most likely have valves hitting the pistons. If you understand the 4-stroke cycle, know the firing order, and know where the #1 piston is, you can verify that everything is happening in the proper order. Pull the #1 plug and stick a long wooden dowel in there. The #1 intake valves will open as the piston drops down. The valves will shut and the piston will rise. The piston will come down as the valves remain closed. Finally the piston will rise and the exhaust valves will open. Suck push bang blow.

Without knowing all the details, I can say the following: When you turn the crank by hand, understand that there is a LOT of force from the valve spring pushing against the camshaft lobes when the lobes rotate against the rocker arms (valve opening). This is the extra resistance you feel in the crank (in addition to cylinder compression). The force builds up as the lobe peak is reached, at which point there is over 100lbs of force pushing against the rocker, but at the exact lobe peak you won't feel any of it since its pushing inline with the camshaft axis. The instant you rotate (pull) the camshaft past the cam lobe peak, the spring, with 100+lbs of force, is now pushing against the other side of the cam lobe. This forces the camshaft to rotate forward...there is nothing holding back the rotation since the chain on the other side is already slack. Because of all the force, the shaft will rotate suddenly, "snapping" forward. It basically jumps and you'll hear the chain snap. On DOHC motors, at some point both camshafts are rolling forward. This will create slack in the tension-side of the chain and, at some point, slack will be created between the camshafts on DOHC engines.

The marks on the links will be off everytime the chain comes around, since the number of links in the chain is not an exact multiple of the number of teeth on the sprocket. The important thing is to make sure that all links are off by the same number on all sprockets.

Study the engine again and again until this is clear. It sucks to put everything back together and find that the timing is off. It REALLY sucks to put everything back together and then bend a valve.

[jrc90240sx]

Can someone host some pics for me, so everone can see. I am pretty sure its not right, but i would jut like to see what others think. i would host them myself, but AT&T got bought out by comcast and i cant load anything up.

[jrc90240sx]

here are some images

This one shows the proper tension on the tensioner side, but has slack on the exhust side

Here is the pic showing the slack on the exhuast side

Here is the slack movie over to the intake side

[DAEDALUS]

As long as your timing marks were aligned right, I don't see any problems. Again, the slack on the exhaust side will happen only when the camshaft rotates ahead of the crankshaft. It might help to bleed the tensioner in a container of fresh oil right before installation. I agree that a noisy chain is really due to the tensioner.

[jrc90240sx]

Sounds good i will remember that with the oil and new tensioner, thanks. the guides already have large groves, and it is very loud from idel to 3k. Its loud enough to be heard from inside the car, and over my exhaust. and befor i stoped driving the car, i was making a high piched churping sound from the front of the engine, that got louded the higher the RPM. I will take some pics when i get the cover off tomorrow. also do i have to drop my oil pan to take the front cover off?

[DAEDALUS]

You don't *have* to drop the oil pan, but it can make getting the front cover back on easier, and you won't have the risk of screwing up the head gasket. As far as I'm aware, most people don't remove the oil pan, but then a few people also screw up the head gasket. Isn't there an upper timing cover on the head, or is it a single casting? I don't see any cover seams in the pix. Since your rocker cover's already off the engine, if the top front came off you could remove it, being very careful to not damage the head gasket. Then when you reinstall, start from the lower cover and work your way up.If no upper cover, then you can try to slide the timing cover in place between the head gasket and the oil pan. Get it under the gasket first, then work it evenly over the lip of the oil pan. It's got to go on pretty straight with little angle.

[jrc90240sx]

sounds good, thanks for the help. I am still prety mad about having to pull it all apart 1 month after having it back up and running

[Structure240sx]

ill go look at it again this weekend when i get time to go over everything thing. porb get a new tensioner jsut to play it safe. thanks for the help any if anyone has anything else ill take it

[trpower7]

Good idea on the new tensioner thing, don't think it's very expensive and if the tensioner goes bad all hell can break loose.