Hi all - I have a 1996 Collector's Edition LT4 that has a few bolt-ons (Tune by PCM for less, descreened MAF, short tube headers, and Edelbrock 7109 manifold). I might be overly paranoid, but either the car has a tick at idle I can't track down or my ears are overly sensative. I've been assured it's not an exhaust leak, and I've also retorqued the roller rockers. Any help in tracking down this tick would be greatly appreciated - the link below has a video of the car at idle. Thanks in advance!

http://www.youtube.com/watch?v=rIWrKKB5HG4

 

Video wasn't much help as all I heard was the whine from the AIR pump. But I understand about the LT4 tick.

The valvetrain on these things is prone to noise due to the roller rockers. Thus the LT4 knock module.

Is the tick a specific, pronounced tick? In other words, I know your rockers make a ticking noise like a sewing machine, that's just what they do. But is this over and beyond that?

What did you torque the rockers to? Spec is 18 ft lb.

The best thing to do is to get a mechanics stethescope and listen to the valvetrain. If one cylinder's rockers sound different from the others than that's where you start. There are alot of things that can go wrong in the valvetrain, but unless there has been a catastrophic event, I would first point to the lifter.

How many miles on the motor? Stock Cam? How does it sound at temp? Does the tick get louder and more pronounced with higher rpm or does it go away? I had a bad lifter, but it didn't make noise until around 3000 rpm. Stethescope found the the #5 exhaust. Lifter change found that the lifter was damaged and so was the cam. I say this from my experience and do not intend to say this is your issue. You may very well have a healthy, normal, noisey LT4.

 

Just got done chasing down a tick/chirp on my LT4. Started by checking roller rockers, ended up having a bad lifter. Just put it back together last wknd. And in asking questions here and researching, it seems it usually is the lifter that causes valve train noises. My lifter was visually bad so easy to diagnose.

 

To answer LT4obsesses questions:

1) yes, there is a pronounced tic on the passenger side of the car - but I think this may be due to the fact that there are less accessories (ECM, etc) on that side of the car to block the noise.. The tic is loudest when the engine is at operating temperature. When using a stethoscope (keep in mind, in the hands of a complete amateur) and listening to various parts of the engine it seems the fuel injectors and fuel pressure regulator are pretty noisey. Everything else seems to sound the same cylinder to cylinder and side to side.

2) Rockers were torqued to 18 ft lbs. per the service manual.

3) Tick seems to go away as the engine moves up in RPM (not noticeable above 2k+ RPM)

4) With valve covers off, everything seems normal and oil is flowing as it should.

Based on below, it sounds like the most likely culprit is a lifter. But just to play devil's advocate, has anybody had noisy injectors (or a fuel pressure regulator) that sounded like lifter tick? The injector's resistance is within spec and they are leak (per fuel pressure leak down test). I'm trying to avoid tearing into the engine if at all possible. Thanks to all so far for your responses!

 

It could be a lifter, and peace of mind vs. cost of intake gaskets is a worthwhile adventure. I know that when I caught my lifter, using the scope I was pretty easily able to determine the cylinder with the problem, but then the lifter was pretty beaten up by then. Yours may not be yet. I would say take the intake off and pull the lifters, not much to lose by doing that and not a difficult task. If it is a bad lifter, hopefully you will catch it before it goes to work on the cam lobe, and it will.

However, keep in mind that these motors are noisey. The harmonics of all 16 rockers, the transmission noise in neutral, all of these sounds just seem to carry throughout the motor.

On a side note, I have always noticed that it seems that valvetrain noise comments/complaints always seems to be passenger side. Mine seems louder on that side too. As you said, probably the open space there. Good luck, I hope it's nothing.

 

My lifter was on the passenger side also. However, me and everybody who listened to it would have sworn it was on the drivers side. As for getting to the lifters, it isnt a terrible job at all. More just a pain of dealing with all the wiring, connectors etc to be cleared out of the way to remove the intake. And oredering new intake gaskets, RTV caulk, thread sealant, and a torque wrench.
In my case the lifter was definately bad.

And because of that, I'm sure the cam is compromised and should be replaced(although the lobe was in actually in really good shape). But if I'm going to replace the cam I'm going to pull the engine and go through it completely. And want to enjoy the car this summer, and take my time and do it right this winter. So found a used lifter, threw it in and WHA LA! Chirping is gone and car runs as good as new.

 

The injectors also can give a noticeable tick - it's a known problem. Think there is a service bulletin on it, but if that is what it is you just have to live with it.

 

yes, that is definitely a bad lifter. and I can guarantee that the cam lobe it was riding on is also bad.

 

Also, sounds to me like the dual mass flywheel has been replaced with the single mass setup. With the other mods you mentioned, I think they probably would have done that also. That was the third mod I made when I got my C4 years ago.

zzzasy

 

Remember, the LT4 has a "net build" valvetrain arrangement NOT having any lifter preload adjustment. All you do is torque down the rocker nuts and you're done.

If you've changed any of the valve train parts - heads, head gaskets, lifters, pushrods, rocker arms - you may well need a different length pushrod IF YOU INTEND TO RETAIN THE NET BUILD FEATURE.

My thinking leans toward the need for a longer pushrod.

The noise you're hearing is the engine trying to tell you some thing's NOT right. I hope you're listening in order to avoid extensive damage.

Of course this is just a POSSIBILITY -Your problem could WELL BE a failed/failing lifter. In any event you've GOT to find out the cause or risk the consequences.

Hope this helps.

Jake

 

Are the rockers the reason for this Jake?