Need help troubleshooting topend knock/tap...PLEASE

[6SENSE]

Hey. guys/gals. Was driving on the highway when all of a sudden my car started making a lot of knocking sounds. I didnt really hear it, but the Casper's audible knock detector let me know something was going on, which I knew couldnt have been KR. I took it easy getting to my destination (maybe a couple miles). The sound wasnt extremely bad at idle (quiet, but you could still hear it), but got louder and irratic when I reved it up.
I was thinking the worse at first (bottom end of motor) but Im pretty sure its coming from the upper valvetrain/topend. I think from the passenger side. Oil pressure was good, never suffered or went down (???).
I took off the valve covers and didnt find anything out of the ordinary. Ran the engine with the valve covers off and saw that oil was making its way up to each rocker, still nothing out of the ordinary, other than sound (when reving it). Took off the intake and pulled the lifters. I could not compress any of the lifters, even with a screw driver or pushrod. I took one apart and emptied the oil that was trapped inside, and was then able to compress it. I thought this was the problem (they arent supposed to be seized up like that, are they??). Rather than do this to all of them and take a chance reusing them, I just went ahead and installed a new set of lifters.
When I got the motor back together and started it up, the sound was still present, maybe even a little louder.
What else could it be? The rocker arm shaft? Do they wear out? Maybe something to do with the nylon "buttons" that hold the rockers on the shaft?
Any ideas?.... please . This car has of late become my families daily driver, since the truck has been running with one dead cylinder and going through rediculous amounts of gas, I cant afford to drive it regularly anymore. Any help is much appreciated.....the sooner the better, thanks!

P.S. cam and lifters have very little mileage (maybe 2000 miles?). The pushrods maybe a little over a thousand miles. Heads were redone as well (new springs, etc.) when the pushrods were put in. Lifter preload was set somewhere between .30 and .40 (I'll have to look up my math to get exact #). Everything had been working fine up to this point, no problems or tapping (other than a little chatter just on start up after sitting overnight, for a few seconds).

 

[6SENSE]

Any ideas??

 

[crazygn]

I'll put some things out there for ya , most sounds to be ok to me so far.

timimg chain[ stock or not] teeth still on it.
make sure the bolts did not fall out of the cam gear.
check the cam sensor out good, could be some noise
converter bolts lose on flywheel

trhats all for now, i'll think about it and be back.

 

[cool 84]

I don't know if it's the best idea to use the new lifters on your used cam. It might not hurt you but it's possible. A blown headgasket can sound like a tapping sound. A bent pushrod can cause the sound. Did you roll them on a flat surface to see if they roll ok? Even loose torque convertor bolts can sound like what you're saying and set off the knock sensor.

Does the sound get louder under load or quieter, or does it make a difference? I think this will separate whether it's valvetrain or bottom end/torque convertor bolts.

 

[Buick From Hell]

wish I could HEAR it! When my #2 rod bearing finally went, WHEN the noise occured is exactly as you describe (hardly hear it at idle, gets worse as you rev it)

 

[6SENSE]

Thanks for the replies guys!

Let me reply to a couple of your questions/comments:
1. replaced timing chain 7,000 miles ago with stock GM sprockets/chain & tensioner. I remember Reds saying that the Speed Pro cam was hard on the stock style timing chain, but not quite sure thats the problem.

2. If it comes to it, I guess I'll have to pull the front cover. Then I can see if the teeth are okay and the bolts.

3. What to look for when checking the cam sensor? Ive heard others mention a knocking sound from a cam sensor, but have no experience with this.

4. I guess I better check the convertor/flywheel bolts, to at least rule it out.

5. I thought it was okay to use new lifters with a old cam, just not the other way around. The cam and lifters that I just took out have only 2500 miles on them. Should I put the old ones back in (in there respective spots, of course)? I have not driven anywhere (0 miles) on the new ones. Probably havent even run on them more than a few minutes.

6. The head gaskets are '84 GM (steel shim) w/ GE1200 and not even a 1000 miles on them. I guess I can do a compression test, but I think the sound gets too loud to be that.

7. I didnt roll the pushrods on a flat surface yet (need to find one ). They didnt look bent to the eye or sitting up against each other, but I know that means nothing. I did notice that a couple of them were sitting pretty close to the head (where they go through the head). Looked dang near like they were touching it. However, I watched them while the car was running and they were turning fine. Plus I think its the rockers that had them sitting close to the walls like that, not the pushrods themselves because they were standing straight (even between the walls of there slot in the head) before the rocker arm shaft was in place.

8. THE NOISE GETS LOUDER UNDER LOAD. QUIET AT IDLE. CAN HEAR IT JUST SLIGHTLY AT IDLE. What does this tell ya?

Wish you could hear it too Kevin, a second ear or eye from someone else with experience with these cars would be great!


P.S. I swapped rockers shafts on the passenger side today and took some time to make sure that all the lifters were pumping oil. Again no problems oiling. In fact the car was idling at 40psi. Also, the rockers were moving up and down evenly (looked like the cam was not worn).

 

[cool 84]

Louder under load is not good. I'm not talking about raising the rpms in park. What does it do if you powerbrake it? If the sound gets louder with load it almost rules out the valvetrain. Valvetrain noise is more dependant on rpm. Every rod knock I've ever heard is pretty obvious. It's a solid knocking sound from deep inside the motor . Much different than a tap. I'm tempted to say if you have to ask, it's probably not a rod. One test you can do is pull one plug wire at a time and see if the noise goes away on a certain cylinder.

 

[6SENSE]

Yeah, that was raising the RPMs in Park. I will powerbrake it and see what it does, but I would expect the same.
Ive heard a rod knock before, its unmistakeable. This is kind of loud, but not nearly that loud. A rod knock will make you not even want to start up the car anymore for fear that something might fly out at you. This sound seems to be coming from up top. Possibly as low as the cam area though.
I put a stethescope on the cam sensor and heard the noise, but it seemed a little hollow there. I put it all around the intake and heard it as well, a little louder. Thats the one thing I hate about trying to find a sound with a stethescope (unless I just dont know what Im doing). Some of the sounds just seem to resonate everywhere.
I will add pulling the plug wires one at a time to the list of tests I need to do. I can just pull them at the coil pack, right? Since you know how difficult it is to pull them on the passenger side. Also, should I bring the engine up to a little higher RPM (where the noise is louder) while Im doing this test?
Thanks.

P.S. almost forgot, if bearings are shot (either cam, rod, crank) wouldnt there be a loss in oil pressure? Just trying to see if I can rule out anything, since my oil pressure is good.

 

[6SENSE]

Also, Ive always remembered noise associated with bearing wear to go away when the rpms go up. I always thought of it as, for example the crank, would balance itself as the speed of the engine rose. Then at low idle where it was more prone to hit you would hear the knocking noise again.
Since my situation is almost the opposite I would be nice to rule bearing failure out. What do ya guys think?

 

[crazygn]

My bearing that want bad sounded hallow and deep , to me it sounds like some thing losing oil press when you rev it but you said you have oil press thow out the rpm range. Cam bearing , ive never heard a bad one myself so not sure. My comp cams lifter were loud and had to be right on the money, my sealed power lifters are not as noisy. Maybe its your timing chain slapping around in the cover but i dont think so. Check the lobs on the cam real good , might have a dead lob.

man i dont know , its hard to say when your not there, hope its nothing bad.