I know what it is. Something between the front crank pulley and the clutch is broken. 
I know what it is. Something between the front crank pulley and the clutch is broken.
dean1484 wrote: I know what it is. Something between the front crank pulley and the clutch is broken.
I actually had a clutch fork problem cause a similar noise on my Samurai...
GameboyRMH wrote: Didn't have time last night, I'll do it tonight. By frequency I mean the number of knocks per second, not the tone.
understand... more revs... more knocks... not necessarily louder
Couldn't find my one long screwdriver, but at least I got the video:
So from my calculations, assuming the engine was idling at 1500rpms (tends to hang there for the first 30 seconds or so of running when cold) the cams should be turning at about 12.5rps. If I make a 12.5Hz sawtooth-wave tone with Audacity, the frequency matches up very closely with the times when the engine's idling. Certainly closer than to 25Hz, which is a closer match for when I give it a little gas, probably coming closer to 2.5krpm.
Well, it's audible and sounds rpm based, are these timing belt or chain, the type of tensioning device would help too.
My 87 4Runner was making a similar sound. I thought maybe a valve adjustment would fix it. Nope. Compression check showed number 4 cylinder about 15psi higher than the rest. I drove it anyway and the next day it went POWEE! Upon teardown the number 4 piston was broken, hole through the cylinder into the waterjacket. I still don't know what the root cause was.
generally speaking and not versed on these engines at all but sounds like tappet noise
I think it spit out one of the shims. I agree, valve noise. Pull the cam cover and check clearances. And don't run it anymore.
In reply to Dr. Hess:
Agree valve train.
Sounds like valve train to me too - like 1/2 or 1/4 engine speed.
Yeah a spat-out shim makes a lot of sense based on the symptoms, and is a relatively easy fix - but I'm dreading that possibility, because other things must be wrong for a 4AGE with stock cams and a conservative rev limit (fuel cut at 7800, spark cut at 8k) to eject a shim.
Edit: Of course other things have to be wrong for the engine to be making these unhealthy noises at all, but bizarre valvetrain problems are frightening.
just take it apart already.
Waiting to hear from the mechanic any time now...I'll be busy this evening so he'll probably call then.
Valvetrain, going with the consensus on spat out (or never installed, just maybe???) shim. Incidentally, that sound is virtually identical to a dead-flat hydraulic lifter in a rocker arm motor, so yeah. Shim.
GameboyRMH wrote: Yeah a spat-out shim makes a lot of sense based on the symptoms, and is a relatively easy fix - but I'm dreading that possibility, because other things must be wrong for a 4AGE with stock cams and a conservative rev limit (fuel cut at 7800, spark cut at 8k) to eject a shim. Edit: Of course other things have to be wrong for the engine to be making these unhealthy noises at all, but bizarre valvetrain problems are frightening.
if it ends up being that it kicked a shim out maybe switch to shimless buckets to avoid an similar future occurrences, theres plenty of info on them on the googlez
Not sure it was mentioned before and it might sound stupid, but could it be the exhaust manifold leaking at the head?
I cant see the video at the moment.
edizzle89 wrote:GameboyRMH wrote: Yeah a spat-out shim makes a lot of sense based on the symptoms, and is a relatively easy fix - but I'm dreading that possibility, because other things must be wrong for a 4AGE with stock cams and a conservative rev limit (fuel cut at 7800, spark cut at 8k) to eject a shim. Edit: Of course other things have to be wrong for the engine to be making these unhealthy noises at all, but bizarre valvetrain problems are frightening.if it ends up being that it kicked a shim out maybe switch to shimless buckets to avoid an similar future occurrences, theres plenty of info on them on the googlez
I do intend to go to shimless buckets, I'll need them in the future anyway, but I'm worried that I'll be treating the symptom instead of the disease regarding this problem. I wonder if the valves might've been very slightly bent somehow, I did have the timing belt go loose back in January.
The engine ran buttery-smooth through 2 autocrosses and a little street driving so I'm pretty sure it wasn't missing a shim the whole time.
I'd really like to think it could be the exhaust header, I've heard of header leaks making loud knocking sounds like this before, but it's on there with a fresh gasket & hardware and I haven't seen any soot marks or heard any change in exhaust sound.
If it's an exhaust leak, you should be able to feel the pulse, and you wouldn't hear it with the screwdriver, err, sthethoscope on the head.
Shimless buckets are gonna cost you.
That motor is non-interference, so the chances of bending a valve are very low.
Pull the top off and let's see what's in there. You find the shim sitting off on the side and it's like, Oh, yeah, that. If not, well, check all the clearances.
A shim can spit out if it is too thick, if I recall. That could be fixed by cutting the seat a little deeper so you would use a thinner shim. Or maybe it was the wrong size or something else changed. It is a pretty rare problem.
Of course, a PROPER race motor, like a Lotus 910 head, has shims UNDER the buckets, where you're not gonna have that problem. Makes valve adjustments really, really interesting.
Dr. Hess wrote: That motor is non-interference, so the chances of bending a valve are very low.
I'm not so sure about that on my engine, I have the HKS 1.6mm MLS head gasket installed.
Dr. Hess wrote: Shimless buckets are gonna cost you.
I've found a place online selling 1SZ shimless buckets for about $12 a piece, expensive for tiny metal cups, but they won't ruin me if brought in the right way 
12*16= Two Bills plus shipping to your little island and the little island tax, AND, you had better know what size you need before you order. That's going to be tricky. I suppose take the existing shim and bucket out and measure with a micrometer, assuming your valve clearance is OK now. But with a stock cam, you should not have spit it out in the first place unless something else went or was setup wrong. I'd fix the something else first. And, at this point, we don't know if that is the problem either BECAUSE YOU WON'T PULL THE VALVE COVER OFF.
Can't pull them off right now, I'm at work I'll pull the valve covers off tomorrow night if I still haven't heard from the mechanic.
if planning on using the 1SZ shimless buckets, you want to start with at least 2, and ideally 8(13751-23030) the thinnest 1SZ shimless bucket. install shimless buckets and check clearances to .0005", like this...
then once clearances are known... order your buckets.
besides the above.... I've heard of, yet never actually seen a shim after it has been spat out... and if it has... the odds are the bucket, and that cam lobe may be garbage.... this is because the lobe easily catches on the sharp edges of the bucket where the shim fits.... also... if the head and bucket are a good fit, I can't see a shim (with a max clearance of .012" - stock cams you said.... ) can spit a shim that is .060" inside a bucket.... not saying it can't happen... just very unusual
Did you use new valve springs??
Mechanic took the car in last night so I should have answers soon.
I didn't use new valve springs. If the cam is damaged beyond (practical) repair I'll replace it with a performance cam the same time. Doesn't make sense to put another stock cam in only to be replaced later.
So measuring the existing shim & bucket height to find the required shimless bucket size as explained here isn't a good idea?
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