KA24DE timing chain help

[ZainRacer]

I have a 91 240sx with 130K miles on it and the chain/guides started rattling a few weeks ago so i removed both the upper guides. This took care of the noise but should I replace my timing chain as well? A few people on a local forum told me that my chain has probably stretched...
Thanks in advance for the help!

Here are some pictures I took when I was removing the upper and side guide.





Upper Side chain guide

[Frankist]

if you had the time and money i would highly consider it, along with doing the sprockets which wear out just as much as the chain.

[ManoNegra]

at that mileage, replacing the timing chain is a good idea
sure one of previous owners didn't do it?
FSM tells you to inspect the links for wear and/or cracks
it's a pain and frankly I would pull the motor to do it

[Cory]

I've never changed the timing chain in any of my engines. I don't see it ever breaking if the engine is assembled correctly and you keep good oil in the car.

[Def]

I really doubt the chain has stretched much or worn out if you never starved the engine with oil.

Is there no tensioner on the top KA chain?

[Matt93SE]

Is there no tensioner on the top KA chain?

Look at pics 2 and 4. It's on the left side of that pic (slack side). He's probably just got it pushed or held back so there's slack in the chain between the cams.

It's easy to let them go slack if you're near TDC and the tensioner isn't pushing very hard on them. The intake cam will spring forward a bit and the exhaust cam will try to pull backwards against the tight chain, leaving the slack in the middle.

[ZainRacer]

I believe in that picture the tensioner was pushed back. I did remove and clean the tensioner while I had everything opened up.

I have always used Mobil 1 5-30 synthetic oil and I change it every other autocross with daily driving miles in between. About every 2000 miles.

Since I dont have a way of removing the engine I am not going to mess with it for now.

[Def]

Replace the tensioner then, or maybe just shim the tensioner some to get a little more tension on it.

[Kingtal0n]

Replace the tensioner then, or maybe just shim the tensioner some to get a little more tension on it.

Care to elaborate Def? I am noticing my timing chain rattle right before the oil pressure builds in the morning of the KA24DE engine with 130k miles. I had never ever opened up a KA engine before, and I looked through the FSM and thought "wow! what a job!" And decided not to touch it yet.

But then I came across this thread and it re-opened my eyes. It appears I can pull the valve cover and go to town, am I right? Is it possible to replace the tensioner and is it safe to remove the guides by just popping off the valve cover with the engine in the car??!

On closer inspection (the pics are tiny) the guy above has the upper cover off, which I thought would require taking the engine out ( to get the lower cover off as well). On an sr20 I would not want to, for instance, pull the oil pump (front cover) without pulling the head... I am seeing now that the KA is a different animal! hmm!!

[Def]

I don't think the upper cover is hard to get off after removing the valve cover.

The tensioner is always easy to get out.

Replacing the guides is probably a bit more work if I'm remembering right.

[Wheelman]

Removing the upper timing cover is a trivial exercise with the engine in the car, once it's off you can remove and replace the upper tensioner, guides and chain. The lower cover is a different story, I wouldn't attempt it's removal without pulling the engine. It requires the oil pan to be dropped which is a PITA with the engine in the car.
You can get a decent look at the lower chain and the guides with the upper cover removed but you can't really do anything with them.

I agree about the chain stretching being a very low probability. The upper is a double roller and the lower is a good quality unit if it's the original.

BTW: The upper chain will rattle on these engines when the oil pressure is low, in fact there is a Nissan TSB to remove the top and left side upper guides and throw them away. I still have the left side unit in mine, it used to rattle a bit on start up and when the oil pressure was low at idle. I pulled the cleaned the top tensioner with WD40 and the rattle went away.

[ZainRacer]

Removing the guides took care of the rattle, I didn't replace anything else. I put around 40k miles on this engine since then including a bunch of autocross events and a few track days and never had any problems with it.