Howdy all,

I did a cam swap about 1500 miles ago, and I'm now hearing a knocking sound from under the driver-side valve cover. It's not quite a tick... it's a bit more substantial sounding than that. The source seems to be pretty distinct; it sounds like it's coming from cylinder 3 or 5.

Lately (specifically today) I've been driving the car really hard. I've had it up to 6800-6900 RPMs several times in the past 48 hours, so I'm sure that whatever has happened was very recent. The car still seems to run fine. When driving it you'd never know there was a problem. The sound is just barely loud enough to hear when inside the car and with the door open. If you close the door, there's no way to hear it over the sound of the exhaust.

I took the valve cover off, and I don't see any needle bearings. I checked the torque on all the head bolts, and they were good. I can't see the springs too well with everything put together, though. I think I'm going to take the rockers off, rock them around in my hands, and see if any of them feel strange. I'll also be able to check for bent pushrods at that point, and I'll have a better view of the springs.

I've only been into the heads once before, so I am not very profficient at diagnosing sounds or identifying problems even if they're right there under my nose. Here are some questions for you...

1) What should I be looking for? How should I look for it?
2) Could it be a lifter? If so, how could I tell?
3) Is it likely that hardened pushrods would bend?
4) Is there any more info that I can provide to help you guys identify the problem?

 

Well, the rockers all seem to be good, and the pushrods were all good. I did, however, find that one of the valve stems seemed to be hammered in a bit. Here's a picture of a good valve stem and a picture of the bad valve stem.

 

Subscribing...... cause I dont know WTF happened on this one!!!

 

Valve float? Collapsed lifter?

In any case, I'd say it's obvious that this head is coming off.

 

Jeez I hope a piston didn't smack into a valve. What kind of heads are you running?

 

He's running stock heads.

 

Yep, heads are totally stock. If a piston smacked a valve, wouldn't I expect to see that on several, if not all of the other valves? This car has been run extremely hard lately, so it hasn't seem 6900RPMs just once or twice.

 

I called Thunder Racing to ask them about my Crane Cams springs (part #144832-16), and they said that I should have shimmed the springs. The guy said that I'm most likely getting valve float but that I probably did not have P-t-V contact because of it. If I didn't have contact, how could the top of the valve stem be smashed so badly? Can valve float do that without P-t-V contact?

 

I guess it could dent the valve from the valvefloat play springing back closed... Damn crane springs, why dont they make it more clear when and where you need to shim. Sorry to hear that dude, but it could be worse. I still think you shoudl do the compression check atleast to make sure the valves are still healthy, just for added piece of mind.

 

Well, do you think this valve is safe to use? I don't want it to chew up the rocker. If it is not safe, I'll just have to replace it. In that case, I won't need a compression check, right?

 

If its really not as rough a texture as it looks in teh picture, then i dont see any harm in leaving it. Worst case scenario is that you have to replace the valve and rocker anyway...

 

I just took the had off (finally). I really don't see any signs of piston-to-valve contact. Here is a picture of the cylinder. It looks pretty clean except for the obvious coolant still in it.

The only thing I saw that looked off about the valve/head is that the bottom of the valve is lighter than the rest. Here is a picture of the bad valve, and here is a picture of a good valve. Is there anything wrong with the fact that the damaged valve is lighter in the middle than the others?

I'll be checking the lifter after dinner.

 

Damn dudeman, that sucks that you had to pull the head. Ill bet its is a shot lifter though... The ligher valves may mean that cylinder was running a little bit lean, but i dont really see any signs or detonation... let me know what you find.

-T

 

I've got a couple questions for you. First, how am I going to identify a "shot" lifter? They all look okay to me. Second, can I reuse the valve seals? The shims won't fit over the retainer or the seat, so I'm assuming they go under the seat.

 

Unfortunately you really cant, unless theres something visibly wrong like scuffing, or busted plunger or retaining clip. Your best bet is to replace the lifters just for piece of mind. Summit has a set of 87+ hydraulic lifters for ~120. Might as well take the other head off if you havnt already. At this point the other heads is barely more than an hours worth of work anyway. As far as the valveseals, once you take them off, I wouldnt reuse them. You can order a new set of valve seals from SDPC or any stealership. Get two sets of brown exhaust seals. You can use the exhaust seals on the intake as well.

-T

 

You have to buy a whole set of lifters? You can't just buy a couple? If I have a collapsed lifter, I know which one it is.

 

^ I think you can buy lifters seperately from a GM dealership, you probably have aftermarkets though so idk. Your pictures are so huge It took 10 minutes to load and I only saw part of the picture lol.

 

I have stockers, but I don't want this to happen again, so I think I'll get a set of the Comp Cams 850-16's. I plan on going FI after this, so I might as well pull the other head and take the opportunity to get ARP bolts, too. It'll be expensive, but at least I won't feel like I wasted my time.

Yeah, I didn't want to shrink the pictures and decrease the resolution. They're all hosted on my web server at home, so the upload speed isn't the greatest.

 

Hey Gauge, is it me or does that retainer on the bad valve stem look like it might be cracked? http://www.ash-can.com/hosted/images/bad_valve.JPG im mean im NO valvetrain expert ( ) but from what little cap swap/VT upgrading expericence i have it may be worth while to check that one....just some food for thought

 

Its a hair. You can see it curl back around and over the valve locks below that.