I pushed my car too hard last night. I have a 400 CI stage one. It now has a knocking noise coming out of the drivers side head. It is not there at idle or light acceleration or cruising. The sound it makes sounds like a bad muffler baffle. Any help would be appreciated.
I have had a problem with the manifold on that side but never a sound like this. I am going out and checking now.
I have been doing battle with a similar noise on both my Stage 1 and Sportwagon. In my case, it appears to be coming from the heat riser valve. There is no gasket between the valve and the exh. manifold. There is a gasket that fits that I have not tried yet. I don't have the # handy, but can get it later. If all else fails, you can use the red hi-temp RTV sealer. It can still be leaking between the head and exh. manifold as well, which will be a task to repair if it has never been off. The bolts are likely to be frozen. Good Luck, Mark
I do have a leak in the manifold. I took off the rockers and checked the push rods they are straight. However I took it for a ride and the sound became a lot worse when gas is given. The sound now sounds like a bucket of bolts being shaken. The sound is directed under the intake now. No sound at idle. The car had a new timing chain put on by the last owner. Could this be loose ? Lifters?
Collapsed lifter, bad cam bearing, flattened cam lobe, cracked piston, cracked rocker shaft, etc... need to do a vacuum test, compression test and like Alan mentioned note any difference in oil pressure.
The compression is good . The sound is coming from the top end under the intake. It sounds like a collapsed lifter with a stethascope. I have ordered new lifter and push rods. Is there anything to look for on the cam when I take it apart . Any break in tips for the new lifters and push rods. Thanks for the help so far
On first viewing this title I was thinking of hangover cures... Anyhow, if one lifter went bad as you suspect, it may be the symptom, not the cause. Check for dirt or residue in the lifter itself. If there is any, you may need to clean `em all out a few times and just generally remove the sludge that builds up in the oiling system over time (grey paste in the bottom of the oil pan). Break in, use plenty of moly-cote on the cam if you pull it out. One question though... it's definitley NOT coming from the oilpan?
Before you pull the manifold, jack the car up, and take off the inspection cover. Take a look at your flexplate, and attaching bolts. A cracked flexplate can sound like a heavy knock or a ticking noise, and everything in between. It won't take you but a few minutes to check, and may save you some unnecessary work. I've seen this many times before. Just ask 69GS400s. He just did his, and he initially thought he hurt the motor, right Alan:grin:
The oil pressure is good 20-35 a idle. When I put the stethascope on the bottom end I can barely hear the noise. I can not isolate it up top where it is loud. I am checking the flex plate right now. Thanks again.
Checked the flex plate and the heat riser. The plate is tight and not cracked. The riser is stuck open and now sealed. I am taking the intake off today. Is there anything to look for on the cam short of removing it? Also is there problems to look for if I install new lifters and rods but not a new cam?
Look at the bottom of each lifter. If you have a problem with a lobe going away, you will most likely see it on the corresponding lifter. Although it should be OK to use new lifters on an old cam, I would certainly use some GM EOS additive. I would pour it over the lifters before I buttoned it up.
Thanks Larry . I have the lifters out every thing is very clean and no problems can be seen. The lifters show little if no wear. The push rods are straight. It appears as if several of them may have been replaced in the past. The cam Looks good what ever that means. No signs of wear. HOWEVER the cam can be moved front to back a bit more than a 1/8 th of an inch. It also appears from a oil sludge line from one of the intake manifol runners there may have been a leak there. Well should I put in the lifters and rods and hope for the best or is there something else I should check?? Everyones help has made this a less stressful job thanks.
Can't really think of anything else, if it looks good. If there are no flattened lobes, it is doubtful the noise is valve related. Is it a heavy knock, or a rattle, or a tap? Hope you don't have a rod bearing problem. If you short out the cylinder, that has the bad bearing , the noise should lessen.
It is a tap that sounds like a like a bucket of bolts when gas is given.At 800 rpm It sounds just like pulling a lifter up and dropping it on the cam. It increases with throttle. I hope it is not down under. I put the stethascope where the cam is all the way down and the sound became lighter as I went lower. Would the 1/8 cam play cause this? The car is apart and the replacement parts came. Is there neg. to putting it back together ?
At this point, the only thing you can do is put it together. If the source of the noise isn't valve related, it's probably a rod bearing. After you start the engine, and the lifters pump up, listen to the motor with the valve covers off. You should be able to tell which valve is making noise. Apply pressure to the rocker arm (over the pushrod cup) to any valve you suspect. If it's valve train related, you should be able to determine that. If that doesn't yield results, try pulling each plug wire off on the affected head. When you come to the cylinder with the bad rod bearing, the noise will deminish or go away altogether. Usually a bad bearing bleeds oil pressure, and you notice reduced readings different from the norm for your engine. Good luck, let us know how you make out.
Get a dial indicator and check the cam, install a lifter and use the dial indicator just like you would when degreeing a cam, this way you can rule out flattened lobes, you'll need to do it to eack lobe and it will be time consuming but while you've got the intake off...better now than later, I wouldn't put it back together until you're sure you found the source of the noise. $25 worth of coolant and gaskets won't make it go away:grin: The cam normally has some movement back and forth when sitting static, the lobes are ground such that when the engines running its held back in place.
How are the actual rockers, valves, springs and rocker shafts? An old Chevy 250 6cyl I had broke a valve spring and it sounded a lot like your issue. Took me several tries to finally see that the spring was broken as it did it in such a way as to hold the valve closed when the engine wasn't running. I'd also check to see if any of the rocker shafts are cracked, retainers and locks are all good and the valves themselves are all looking good from the top. Check to see if all are the same height, the valve stem sticks out the same amount and that all of the keepers are there. What exactly happened just before this noise started? Float the valves, over-revved the engine? I spun a rod bearing in a 68 Riviera racing a 240Z a long time ago. I had the engine turning about 5800 RPM for about six miles of freeway. (Late night, 19 years old. Don't ask.) I did win though..... It's a pretty definite sound though. If you ever heard an engine with a bad rod bearing, you'd know any other time you heard one.
