I have some ideas, but I want a second opinion.

It's a brand new build, just breaking in the cam at 2k RPMs and about 15 minutes in it started doing that.

I popped the valve covers and reset lash in case it was lifters tapping.

Fired it up agian and the noise hasnt changed...
http://s6.photobucket.com/albums/y22...t=100_6711.flv

Oil pressure was 59-61 psi according to the electrical gauge, but it has a new sending unit so even if its not accurate it's in the ball park.

 

sounds like lifter tap to me,also sounds like timing is too high.try turning timing back a little to see if noise gets better,later jimmy

 

I've been too close to this thing, fussing over it for it seems like forever, a second opinion is exactly what i need.

And how will retarding the timing get the lifters to stop tapping?

But I will put that on the to-do list.

 

^ I think Jimmy was referring to the noise just before the video ended (regarding timing).

 

Ah....

I just figured a motor cant shut down completely from 2k RPMs without sucking a little more fuel and spark down. But that makes sense too.

Since I've got Comp Pro Mag rocker arms, I set lash the lazy way by just tightening the rocker nut onto the poly lock gently to the lash points I set it at last time (A few of them did back off) but I guess that didnt do the trick, so I'll reset lash the proper way and hope the tap will go back to the bowels of hell where it came from.

Is everyone of the opinion that it's a lifter? Could that be caused by wiped cam lobes?

 

Your absolutely right! That's why I referred to it as just noise, and not spark knock, because you were idling too high before shut down....

 

I think it's a rocker. Don't think it's run long enough to wipe a lobe. Even if it did, you would have had to turn one of the rocker nuts more than a turn when you readjusted them.
Can you post some quick notes on the build?

 

.060 over 2pc RMS 350 with 4-bolt mains and a comp XE262 camshaft. 218/224 @ .050 and some Vortec heads with 1.94/1.60 valves. Pretty straightforward really.

And I've had so much trouble with this build it's ridiculous. This is the THIRD time I've tried to get it broken in I think. The first time the heads I got from Dans87GTA and accomplice Shagwell turned out to be junk and I had to tear it down and put new heads on it. Then I ran it for several minutes (around 10) the first time and realized I had some lifters tapping that time (Through the drama I had mistakenly identified it as an exhaust leak, but it was the lifters/rockers) and so I took it apart, put break in lube all over hte lifter feet again, and did he valve lash again. The first time I took them to 1/4 turn past zero lash. THis time I took them 1/2 turn past zero lash.

It's got pro mag rockers, so I dont know why the rocker nuts would be loosening up, but they are. I tightened them down to where the poly lock engaged and I haven't checked to see if they just immediately loosened themselves or what, but they're all tightened down to where I set lash the other day at 1/2 turn past zero lash.

So now I'm going to just go ahead and do the whole sequence again and reset lash, and see if Iget some funky things going on.

LIke I said, the last time I did this I actually pulled the intake off and recoated the lifters with break in lube so I'd feel better about turning it, but in the process I actually got a good look at every lifter and all of them looked great except one that looked like it had a sketchy moment or two, but it had a nice spiral-circular pattern developing on it too, so I figured it would be fine and would work itself out.


So I dont know... it's run probably around 20 minutes now, actually. I was hoping to take it another 10 at 2k RPMs, but I seem to ahve the worst luck.


Here is the one funky lifter. I couldn't feel any of this with my fingernail and it had only run for about 10 minutes, and judging by the rotating pattern developing I figured it'd be fine.



Its hard to tell in the picture, but to me it looked like it got kind of stuck for just a moment in two different places and then started rotating like normal.

 

Don't jump to conclusions, it's more than likely just a loose rocker arm. Try wiggling each individual rocker with the engine off, and when you find one a little looser than the rest, you found the culprit. Tighten in increments of a quarter of a turn only, just until the noise is no longer prevalent (you should be able to slightly move the rocker pressed against the pushrod left to right with the valve fully closed, but not up and down)....

 

I actually just did that, good to see I'm thinking along the right lines. I also made a video of what I found. Please excuse my horrrible accent, LOL.



My logic is that those poly locks are NOT going to move. The nuts themselves may loosen up, but hte poly locks are in the same place they should be, so as long as the nut is tight against the poly locks, that's where I properly set lash earlier.

So the question to me is, why would there be slack there unless the lobe is goig away? I mean I can tighten it down and run it some more... but if the lobe is toasting itself, then that will only end in heartbreak. I'm trying to rationalize something out... but with the poly locks... Im not sure there's another explanation.

 

Are you sure the stud isn't pulling out?

 

I would lean more toward a collapsed lifter first, then a wiped cam lobe. A collapsed, and/or sticky lifter will cause the same exact noise, and is very very common. Picture a lifter, when compressed, staying like that for a tad, even when pressure is released. The pushrod, as well as the rocker, will make the same exact noise from the video, it'll slap into one another...

 

So you think a collapsed lifter is more common?

I mean i've got this thing filled with rotella, got comp cams break in cam lube (assembly lube type stuff) on the feets of the lifters, and then I've got comp cams break in additive in the oil also. The only thing that worries me is how hard this hing was fighting me at first to get started... it took several tries to get it to fire and stay running. But the other two times we tried to break it in, it fired right up. Im thinking the timing was just off this time, but either way it's something that's got me concerned... but like I said, I've taken as many precautions as possible and this thing hasnt run under 2k rpms much at all yet aside from firing up and shutting down.

They're screw in studs. They're not goig anywhere. Nice idea, though!

 

Did you shoot oil into the lifter before installing, or did you just bath them in assembly lube? It's possible one of them is a tad dry, and in time will eventually fill up with oil. Sticky lifters are very common, unfortunately....

 

Yes, that would tend to make them a little less likely to pull out. ;-) Since you're worried about the cam lobes, I guess a quick acid-test would be to pull the rocker arm off and measure the pushrod travel with a dial indicator.

 

THats a good idea I may try that before I go out and drive it.

I had a friend of mine out here who knows a lot more about his stuff than I do out messing with it and since we knew which rocker it was that was rattling he went ahead nad set the lash on it while it was running, and we let it run about 10 minutes or so, and the tap hasnt come back yet. TIme will tell whether it's okay or not unless I do the dial indicator trick which is pretty smart. I wouldnt ahve thought of that...

But here's a video of it idling!

http://www.youtube.com/v/LcBIwOHn4ZQ


So how do I determine whether it's a collapsed lifter?

 

I have had a slight problem with my new build. I took the intake, rockers and the lifters out. I am taken the lifters and letting them soak in Oil for a couple of days. I am 100% they are weren't pumping up properly. I would not rather wait until they get pumped up with the engine running.

 

I had what sounded just like a lifter when I started my 350 for the first time after a rebuild. Turned out that I had cocked the distributor cap somehow causing the rotor to hit the side. Just something else to look at.