Hello, I am having trouble understanding what is going on with my K24E engine.

I have a 1990 Nissan 240SX (130,000 miles) in good shape except for a few things with the engine. Right after buying the car, a nasty rattling within the front of the head became more and more apparent and the rattling would be most active at around 2,000 rpms... So I soon realized it was a bad tensioner and railguides and about two weeks ago installed a new timing chain, tensioner, and railguides (these were not OEM parts, they were bought at a local aftermarket auto parts store). After tearing the engine apart, sure enough, one of the old railguides was broke apart and most of which I could not find anywhere in the engine (maybe in the oil pan?). Now the new timing kit is installed in my engine, and I *still* get a rattling from the head. It is not exactly the same rattling as before, but my feeling is that it could still be related to the timing chain as the rattling is not constant through all RPMs. It isn't as loud of a rattling as before, and the rattling doesn't go crazy at 2,000 RPM's as before. It is not a ping or a knocking sound- it is definitely a rattling and I just don't understand how the timing chain could still be hitting against something with a brand new tensioner (also, as I mentioned before the noise is somewhat different than before, but still a rattling that is NOT constant at all RPMs). Is there something I missed when installing the chain? If it is not the timing chain, could it be the rocker arm or the follower? Would the rocker arm make a rattling sound that is not constant during all RPMs?

Any help would be appreciated as I am sort of a novice at trouble shooting engines, etc.. Thanks!

 

Ok, after doing a search on this forum, there are a few other things worth mentioning:

The rattle occurs at idle as well as during acceleration, however, at about 2500 rpms it changes pitch and then at about 3500 the rattling disappears.

I had a coworker who is a transmission engineer and knows a little bit about cars listen to the noise. Before he listened to it, I thought maybe the rocker arms and lifters are making the noise, but he suggested that the noise sounds like it is still coming from the front of the head *and* the noise dissapears about 3500 rpms (as the resonance of the chain changes) so it sounded like the chain to him.

I just don't understand how it could be the chain though with *all new* rail guides, tensioner, and chain, and top gear.

Is it possible that the camshaft might need to be looked at? Is it possible that the rocker arms and lifters might be the problem? Like I said, the rattling happens at idle and doesn't change a whole lot until about 2500 rpms, then it changes in pitch, then it disappears at above 3500-4000 rpms. It is not an extremely loud rattle either (can' really hear it on the highway) but it is loud enough to hear at a stoplight with the radio off.

I just don't want any problems with the timing chain or any valves....

Thanks again in advance for any help, suggestions, ideas!

 

free bump


wish I knew more about this kinda thing.... if no one here can help, maybe try freshalloy.com?...

 

your cam timing is off

i'm the timing chain guru.
do a search for rudeboy and guru
you'll seee

 

I'm not sure if the cam timing could be off because she started right up like a champ after replacing the chain....

I realized *after* posting this that it was maybe posted in the wrong section, I apologize.

I still wonder if anyone else has any input on this, I've done searches on this forum and haven't found anything that zeros in on exactly what my problem is....