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Old 03-04-2003, 09:23 AM
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Post valvetrain gurus: need help identifying mysterious valve noise

Hello all,

I'm a new user to this forum. I recently installed a new motor in my '69 vette. It's a chevy 350 with casting numbers from 1970. I bought the motor with the lower end already assembled, having been bored .030 over, with new pistons, rings, bearings all around.

On top of the block are a set of infamous "882" heads, which I know are prone to overheating and have generally poor flow characteristics. The history I have on the heads is as follows: crack checked and cleaned, mild 3-angle valve job, replaced exhaust valve guides. It was assembled with new valves, springs, retainers, valve locks.

I installed a brand new set of (albeit chinese made) Proform 1.6 ratio self aligning roller rockers (which means i don't need guideplates, right?) and measured out a set of comp cams heat treated pushrods. The hydraulic lifters were brand new, and the cam was supposedly a new corvette cam with .480 lift on 1.5 rockers. The springs were tested for pressure and coil bind at compression for 1.6 rockers and supposedly checked out ok.

Now... for the symptoms. Originally when I installed the motor, the intake spring on the number 6 cylinder made a "clicking" noise just as it started its compression. I assumed this was merely the retainer and the spring surfaces becoming accustomed to eachother. But now, after running the engine a little, I get a reasonably loud tapping noise coming from this valve / rocker. I had theorized at one point that perhaps the 1.6 ratio rocker was too aggressive and that the roller was going off the edge of the valve surface, causing the noise. but wouldn't it stand to reason if the ratio was too great, i would get noise from the entire valvetrain? I ran the engine with the valve covers off and placed a screwdriver in each rocker stud to listen for noise and there is a pronounced tapping coming from only the #6 intake valve and a slightly less severe tapping from the #6 exhaust valve.

I checked for exhaust leaks, which had been causing noises before, but there were none. I checked the torque on the fuel pump bolts and they were tight. All I'm left with at this point is wondering about that valve spring on the #6 intake. that "clicking" I heard when the engine cooled down after the first couple starts has since gone away, but the fact that tapping is coming from the same valve seems more than just coincidental.

I tried adjusting the locking nut on the #6 valves (both intake and exhaust) while the engine was running, to see if the noise would go away... you know, if there was too much lash in the rockers. the noise didn't go away.

I know my question is rather complex... I'm wondering, if the cylinder heads originally had to have the exhaust valve guides replaced, does it stand to reason that the old guides were worn heavily to require the procedure? Would it then also stand to reason that the noise from #6 intake could be due to valve guide wear in the intake valves (which didn't get replaced)? What should I look for now, what else can I try? I've spent hundreds of dollars putting this motor together, and I need to resolve this issue in a reasonable budget, hopefully avoiding having to pull the cylinder heads off.

Thank you very much for your time, I know this was a rather detailed description of the problem... hopefully it will aid you in your diagnosis.

The Blonde Weasel
San Diego, CA

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Old 03-04-2003, 09:51 AM
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You don't tell us if this is a manually adjusted solid lifter or a hydraulic flat tappet or a roller tappet and this will make a big difference in what the solution will be. I will assume though that since you didn't talk about manually adjusting the valves that it must be a hydraulic tappet. You don't talk about any adjustment, so I am assuming that you did not adjust them. Maybe you just screwed them down until slack went out of the valve train, they all pumped up except for number 6. It is also possible that number 6 is not pumping up, I will deal with that later.

If it is hydraulic, you need to go through an adjustment process because what you have may be an engine full of lifters that are too tight. Here is the adjustment drill:

Take off one valve cover and if possible rig up some sort of dam with rags to keep oil from dripping down onto your exhaust manifold. Start the motor and with the engine running,start at the front or rear of one bank and loosen one rocker nut at a time until it makes a good clatter, then tighten it until the clatter dissapears and then turn 1 1/2 turns additional. Let the engine speed stabilize after every adjustment and continue until all valves are adjusted. Replace the valve cover. Then go to the other bank and do the other valves. This should stop the noise you are talking about.

Now, if you still have the noise, take a look at the offending rockers. There should be oil coming up the push rod into the rocker and flowing down onto the roller tip or centering notch and onto the valve stem. If oil is not coming up, you are not getting oil into the lifer bore. It is this oil that pumps the hydraulic lifter and probably means that there is a clogged oil passage in the block. The cam itself is splash oiled.

Hope this helps.

[ March 04, 2003: Message edited by: F-1Rodder ]</p>
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Old 03-04-2003, 10:04 AM
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Thanks for your response.

The lifters are hydraulic. Now, I had heard a conflicting method for adjusting hydraulic lifter lash. I followed the method of adjusting the lifters with the engine turned off, by turning the crank at 90 degree increments and adjusting each rocker lash while at TDC for that cylinder. (i.e. when #6 cylinder is "rocking", adjust #1 cylinder rockers) I was also told to tighten the rocker nut until the pushrod would just start show resistance while i was spinning it between my thumb and my forefinger. This, theoretically would be the point where slack was just taken out of the system. From there, I was told to only tighten the rocker nut 1/2 turn further, to put approximately .03" of preload on the hydraulic lifter.

What would be the consequences of adding another full turn to the rocker nut? It would put a greater amount of preload on the lifter. how would that affect lifter performance across the powerband?

As for oil, every rocker looks real good, the oil holes are all supplying a generous amount of oil to each rocker.
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Old 03-04-2003, 10:20 AM
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take a peek at the clearance between the pushrod and the cylinder head where the pushrod hole is. Many times with 1.6 rockers there is not enough clearance and the two make contact and cause a binding condition. Check the clearance through an entire cycle.
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Old 03-04-2003, 10:37 AM
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It's also possible for one of your intake bolts to be too long, contacting a pushrod. Not sure if that would effect the #6 valves though. Pull the #6 pushrods out and look for scoring.
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Old 03-04-2003, 11:19 AM
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I'll pull out my #6 pushrods and look for any unusual wear when I get home tonite.

My big question is... If I had excessive valve guide wear on my #6 intake valve, what kind of a noise would that make... could I get blowby under combustion conditions, causing a tapping sound? It seems to me if the valve guides were worn, then I would get oil fouling of the plug on that cylinder. All my plugs are running clean, except #2 cylinder, and I think that's cause of abnormal ring wear for that cylinder.
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Old 03-04-2003, 12:26 PM
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OK, this is making sense to me. I now believe even more that you need to go through a running adjustment. The lifters will not all bleed at the same rate and a manual adjustment will get them close, but will not compensate for lifters that bleed a little faster than the others. A lot of guys will adjust the running lifters 1 or 1/8 turn, but the repair book says 1.5.

But at least you have convinced me that the lifters are working.

One more thing, you didn't give specs. on your cam profile. A more aggressive cam will always produce more valve train noise. I don't think this is your problem because you would hear the noise all accross the motor, not just one lifter.

[ March 04, 2003: Message edited by: F-1Rodder ]</p>
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Old 03-04-2003, 01:48 PM
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This suggestion is way out in left field but bear with me.

I once seen a similar motor and it had much the same symtoms you describe...except on three valves. After much oil spillage on the exhaust doing all kinds of adjustment to the rockers and choking on enough fumes that would kill a horse I decided to remove all the rockers from the affected side of the engine. I could find nothing wrong and switching rockers from valve to valve accomplished nothing except to eliminate these components from the equation (give it a try).

After much head scratching I decided to remove the spring from one valve to check bushing clearance to the retainer (check that too at full lift). Lo and behold I found that the new bronze heavy wall liners "pressed" into the castings were loose and were occillating back and forth between the valve head and retainer cap, that was why it only clicked at idle not at speed. Oddly enough the engine ran fine and really when you think of it why wouldn't it, the valve was only riding in a "special" floating bushing.

Upon the disassembly of the head it was found that whoever had pressed in the liners had not deburred the casting at the top of the hole and consequently when the new liner was pressed in it shaved the OD all the way in leading to a poor press fit. The entire head on one side was affected and many of the liners were only a light tap fit, the other head was fine.

Unfortunetly the only way to see this was to remove the spring and check to make sure the liner is at the top of the hole and it is tight, little brass shavings might be found under the umbrella seal as a clue. Told you it was weird, but honestly I just got lucky because the guy told me the heads were "just done" and that lead me to suspect the machine work.

Another method I could have used was to loosen the exhaust or intake and peer through the port and see if the liner has fallen down around the valve stem, easier said than done I know.

Hope this nutty problem helps you solve yours, I would pull the heads if you are even a little unsure.
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Old 03-04-2003, 04:19 PM
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4-jaw is not the only one who has run into the loose bronze liner thing, i get a few in every year, this will drive you nuts trying to find the noise if you haven't been there before. Last year i got in three sets of heads from a rebuilder and the wrong size liners had been installed, they just floated up and down with the valve, this should have been noticed in assembly!
Your noise could possibly be excessive guide clearance.
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Old 03-04-2003, 05:48 PM
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Hasn't anyone noticed that the 882 heads have giude slots in them and he's using "self aligning" rockers.

Maybe there's binding going on at that valve. It may not be heard on other valves because we all know that not everything is machined correctly. This is why it's not recommended that self aligning rockers be used with other giudes, Cast or Plate style. Make sure the offending valve isn't sitting on the edge of rocker tip creating noise. Try putting on the stock rocker for a minute to see if the noise stops. If it does it's gotta be in rocker assembly. If it doesn't than it's gotta be some where else in the valve train. If the latter is found than follow the god like advice of 4- Jaw. You can gringd the slot in the head a little bigger to relieve the binding of the pushrod and rocker so ther are not to work agianst each other.

Hope this helps
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Old 03-04-2003, 07:59 PM
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well after a couple of hours of fooling around tonight, i finally came to the conclusion that I had been cranking on my exhaust header bolts so tight that it caused the center ports on my passenger exhaust header to become slightly deformed. I pulled out the exhaust gasket and sure enough there was black markings coming from the middle between the #6 and #4 exhaust ports. I'm going to replace my crappy paper mr. gasket pieces with some nice percy's or SCE dead-soft aluminum or copper molding gaskets to make for a better seal. I think this should solve the problem. I have no idea how my header face got so deformed, I guess its just from years of cranking on those exhaust bolts to make sure they were tight.

thanks for everyone's help on this mystery, i've learned a lot more about valve guides and such in the process. I'm happy to have found a forum with knowledgeable gearheads. I used to be a member of the corvette forum, and those guys tended to be a little high on their horses, all they would ever talk about was how great *their* engine was, or which parts you should use because *they* used them. Its nice to find other people who believe more in the importance of automotive theory than just what works for their particular application.

Cheers

The Blonde Weasel
San Diego, CA
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