T_Vert

I was really thinking it was valvetrain related but i just cant see hwo it can be anymore. Ive been doing some reading and some others have the knock occur duing similar circumstances to me. Basically when you free rev it you hear the sound rom 1500-3000 or so. When you get ont eh gas some it goes away if in those rpms and it'll be back on decel in those rpms but usually only when coming back to decel at idle. I tried to rev it and pull an injector at a time to try to pinpoint it but it didnt seem to affect the noise.

http://tech.cfbinc.com/dave/valvetrain.avi

Dave

Dugmole

Sounds like a lifter to me.

T_Vert

the sound im worried about occurs 12 seconds into the video. If i had a bad lifter the rocker the bad lifters is on would be loose when the valve would be shut wouldnt it (that valves base circle)?

Dave

STA-BLK

Man that is EXACTLY what mine sounds like.The dealer keeps saying its piston slap but i dont know.Im going nuts trying to figure it out before my warranty is out.

98vert6spd

rod knocks get a double ound to them
and that kinda sounds that way to me
I had a honda prelude that did the same thing for about 700 miles before i couldnt get it to run anymore never did throw a rod or anything like that
it jsut ultimately wouldnt idle and it started griding really bad
I think ti was a rod bearing


if its still under warranty just drive it till it breaks

T_Vert

well this occured right after a heads/cam swap thats why im concerned. its very loud outside the car. its not there at idle either.

dave

Threed

IMHO it sounds like slap to me.

Av8ter

Your sound is definitely upper valve train related. A rod knocking sounds like taking a rock the size of your hand and knocking on your door with it. Its a lower decible heavier sound. Also, that sound that you hear has nothing to do with an exhaust leak, your injectors, or piston slap either. These type cams that we use have a very high ramp rate, in which the valves open and close very fast. Alot of the ticking noise (sewing machine) you hear is actually the valves slamming closed on the valve seats in the head. When I first got my Z06, this sound was pretty audible when the rpm's were around 1800 or so. Many people were concerned about it but later found out that it was normal. When I installed my cam, which you can see in my sig, the sewing machine noise became even louder. People ask me about it from time to time and I tell them its normal and is because of the cam profile. Im not sure if its as loud as yours because its hard to tell from that camcorder or how sensitive it might be at picking up that particular sound but it sounds pretty close to it. If your lifters were bottomed out, you would know it. The car would run like crap and you would have a lot of backfiring and popping. Youve got stock rocker arms, so you just torque those down. And I assume you are using the the correct springs for that cam. If I could hear it more in person it would be easier to tell, but yours does sound louder. The only thing I might think that it would be is the lifters arent pumping up. After you run the engine, pull a valve cover off and look at one of the valves that are closed. Take that rocker arm off and see if you can push the pushrod down into the lifter. It should be pretty hard if its pumped up with oil. If it pushes down very easily and springs back up, then I would say your lifters arent pumping up. It may be hard to tell because that lifters travel may already be depressed a small amount from the valvespring.

T_Vert

its not piston slap as the problem wasnt there before.

Dave

T_Vert

hey, how confident areyou its not bottom end related? The sewing machine im not worried about. Its the change in tone and the loudness it gets during a certain rpm. its very loud and embarassing. YOu can hear it well on sidewalks and people already look at the car as i knock past.

Dave

Av8ter

Is it an auto or manual trans? If its an auto, you can put it in gear, keep the brakes on, and give it some throttle to load the engine up some. If its a rod knocking, you would normally start to hear it there. But since you didnt do anything to the bottom end, I would find it hard to believe that it would be a rod knocking that quickly after just a head and cam install. Unless you forgot to put in oil after the assembly and ran it dry on oil for quite some time upon the first start, which i doubt you did. I read before that you didnt touch the oil pump and youve got oil pressure so i really doubt its the bottom end. I dont see how anything you did would effect that.

T_Vert

its a manual. I can load the motor by putting the ebrake on and letting out the clutch in 1st. what should i listen for? i did probably run 2 qts or so low on oil at one point. NEver did loose oil pressure but my front crank seal was leaking pretty good. So i thought maybe that had something to do with it. Is there anyway to diagnose a collapsed or partially colapsed lifter?

Dave

01vetter

Get youself an engine stethoscope! Definitely will help you listen "inside" the engine and isolate where the noise is coming from. Costs $20 or less.

Good luck!

Av8ter

The 2 quarts of oil wont hurt anything. Usually if a rod is starting to knock, sometimes it will knock while idling or if its not quite that bad yet, it will start knocking when the engine is starting to load up when you put pressure on the pistons, like taking off from a dead stop or something. It will sound like what i mentioned before with taking a rock and knocking on a door with it or a hammer on a workbench. But like i mentioned before, I doubt you have a rod issue.

As for testing the lifters. Hmmm. Run the engine for a few minutes to get it hot and then pull the valve covers and check for loose rocker arms for starters. They should be pretty tight on the valves and pushrods. If you find one that has alot of spongy feeling when pushing the pushrod towards the lifter, then I would say its not pumped up with oil, assuming the valve is closed. Obviously if the valve is open, youre not going to be able to push it.

T_Vert

i have one and cant pinpoint anything!! The noise is the same througout the motor. The loudest i hear it is at the exhaust manifold on the metal heat shield. Its is twice as loud on the shield as it is on the actually cast manifold. no header leaks though

Dave

T_Vert

ok, ill try pushing on the back of the rocker where there pushrod meets it. All rockers are getting oil to them, if the lifter is getting oil shouldnt it be pumping up? I guess i dont fully understand the design of a lifter. Can a lifter partially pump up? IE, lower rpms it doesnt have enough flow to pump up and this causes lack of preload? Or would it either be fully depressing when you torque the rocker down? If that was the case, you'd think the pushrod would still be lose wouldn't you??



Dave

Av8ter

From your video, it seems the sound is throughout the engine. Sometimes one lifter may not pump up, but not all at the same time unless no oil is getting to them. Even if oil is getting up to the rocker, if there is a little dirt or trash in the lifter it can cause it to not work properly. But since all the sound seems to be throughout your engine, I doubt all your lifters are bad.

Lifters are pretty simple in design. Once you pop the snapring out, there are just a few pieces in there. When properly operating, it has an internal piece that acts like a checkvalve which helps hold oil and will automatically adjust itself to the proper load for the valve. Anyway, if it was fully pumped up and you did torque the rocker down, it would usually start to open the valve. When you shut off your engine, some valves remain open obviously if they are on the lobe of the cam and the lifter will remain pumped up. Sometimes they do bleed down, and thats when you hear an engine start up, it will tick for a few seconds and then it will go silent and operate normally, because then the lifter pumped back up.

Anyway, thats about the only thing that i can think of is the lifters dont seem to be pumping up. I have a ticking sounds in mine but not as loud as yours. If you find out something, let me know.

0Jeff @ TPE

Thats definately not a rod knock. I've heard many rod knocks before and it sounds NOTHING like that. I would say its in your valvetrain. Lifter, Pushrod. I had a valve seal come loose on my Blown 455 in my boat. It sounded exactly like that. But thats because the piston was hitting the top of the valve.

Pull the heads, dont keep revving it cause somthings making metal to metal contact. I'm sure you'll see what it is as soon as you pull them.

And NO its not piston slap...

Dope

Yeah I'd take that apart and look it over. Something's not right in the valvetrain. Don't keep running it and ruin something.

Dope

George8211

Sounds like lifter noise to me... Rod Knock is a lower hollow sound.

Lets see what we can find...

http://remanufactured-engines.com/page4.htm

Piston Slap