Chronic valve...Break through this evening!!!!!

[norustscott]

I am pleased to announce that the problem is not with the intake valve or seat. please read on...

Now, I must worn you. What I am about to disclose goes against everything I have been taught regarding engine building. However, I was at the end of the rope...


The saga contiues with me laying flat on my back looking up at the bottom of the engine and trying to convince myself that RIMCO had just done a bad job on my head. (spark plug threads aside) I just could not believe that teh seat would fail...) So, per the last thread I took Otto's advise and backed off the strainer nut to about 6 ftlbs...but before I quit I got the bright idea to start eliminating some of the variables in the valve train, so I swapped the rocker from the problem valve, number 4 to intake 3.

The next test run, about 150 miles, ended with a tight number four valve. Back under the beast...

Here is where some will whence. I decided to move the lifter and push rod from number four intake to number 2 intake. a swap...( rationale, I fingured that both lifters have a relationship with that cam lobe and although slightly different would hopefully have little impact.) I did the normal re-adjusts and off to a road test.

This road test was interupted by the number one spark plug ejection...repaired with a Timesert sleeve. Worked very well. (My in car process included greasing the reamer/ tap, a shopvac in BLOW mode on the tail pipe and the exhaust valve adjusted open.) more on tha later if you want the details.

So, back on the road again. I logged jsut about 200 miles since the (whence) swapping of lifters and push rods and ...


Drum roll please. Guess which valve is tight now.....


Number 2 intake! Are you kidding?! No I am not!....

the tight valve starts to surface with a slight miss at idle. then it progress to a lopeing idle. Pull a plug wire or an injector and there is no noticible change. This pointed me directly to cylinder 2. A quick compression test reveled 90 psi. I must admit that I was disgusted but also had a goofy grin on my face.

Quickly jacked the car up pulled the wheel and popped the valve cover off. rotated the engine to TDC number 2 and ... even thought the engine is hot there would be some clearence right? but no..zero clearence on the intake. The number 2 exhaust measured about .004" hot.

Confirmed that the problem follows the lifter/pushrod assembly.

BUT WHY!!!!!!!!!!!!!!!!!!!!!


Could this lifter be hanging up in the lifter bore? It showed no evidence of abnormality when I had it out.

The push rod is not bent nor did it appear to have lifter to pushrod cup seat alignment problems.

My thought was to swap out the push rod with another and see if the problem follows the rod? Or, just repalce them both with spares. How would yuo guys handle the lifter? Buy a new stock or try and use a good used one ( if there is such a thing).

This is the the point where I ask you guess to suggest next moves...

Thanks agian for all of the brain power to date.



Scott

[Tom Perso]

Hmmm,

Do you have a picture of that lifter?

Are you SURE it isn't some kind of hydraulic lifter? Thats what it sounds like to me. But, weirder things have happened.

Pictures tell a thousand words.

Later,
Tom

[JWest]

The cam/lifter interface has always been an Achilles heal in these engines, and the quality of parts in the last few years has seemed to have degraded making matters worse.

I'm glad you have narrowed the problem. What cam and lifters did you have?

[norustscott]

The cam is an OEM NOS FI part. Came in a Porsche/Audi box with the correct 2.0 l part number. The lifters are also OEM Volkswagen part. Purchased as a set in the original vw box....My thought was to get parts that where of the same vintage and possibly a matched material hardness for Lifter/ Camshaft compatibility...I am planning to take out the lifter tonight. I will try and post pictures Friday.

BTW. Can anyone confirm the construction of a solid lifter. After studying the one sitting on my desk I am sure that it is made of at least two pieces...Theory, Can the two pieces become loose? Oil pressure pressure would force the inner part out and would take up the .006 clearence...only to wedge on the next lift stroke....

[Jake Raby]

I have seen this just one more time with a stock lifter.

Yes some lifters are two piece and can do this.

The stock cams do not go flat often, but do have issues. Issues that the web Cams do not.

I hope you found the issue, however rematching a lifter to that cam may require changing the cam. DO NOT try a brand new lifter in that hole, you gotta go with another used one, and that may not work either.

[sleepdoc]

Jake,

Why not a new lifter?

best Mark

[Jake Raby]

It'll consume its self, or the cam in no time flat...

The cam and lifters MUST be ran in as a set. I have put an old lifter in an engine like this, that had a blown Hydro lifter. It lasted 5K before the cam and lifter both wiped out..

Once I put a new lifter with a used cam it never made it out of my driveway before it ended up consumed, in the oil filter!

Cams and lifters do not play, they have the bite of a Pit Bull!! In my opinion, they are the weakest part in the TIV, next to the cylinder heads!

[sleepdoc]

Jake,

Thanks for doing all the wrong things for us first. You
keep all of us from spending money learning what you
already tried twice.

best Mark

[norustscott]

I assume Camshafts and lifters, to be compatible, must share similar properties. Steel makeup, temper...

When you break in a new engine with a new cam and lifters we are instructed to run them at no less than 2500rpm for 20 minutes and again after a cool down and valve adjust.

I assumed this was to "temper" both the cam and the lifters. Over time they develop a wear pattern...a mating of the two. In my case I figure the best alternative would be to install a used lifter with a similar wear pattern as the old lifter. The used lifter would be "tempered" from previous use and would not be eaten by the cam. On the other hand, A new lifter would have to be tempered or it would be softer than the cam and would be lunch in no time. The only thing I have going for me is that the engine is fresh just under 4k miles.

The cam face shows no wear. definatly no signs of wearing through the harden surface of the lobes. My concern is the dissimilar wear patterns, although very slight, between the existing cam and the replacement used lifter will cause a premature end to the cam/lifter.

My plan it to compare what little wear does exist with the handfull in the shop and pick the closest.

If it does fail and chomps the cam or the lifter... I am stil looking at having to split the case and replace the cam and lifters...and possibly bearings.

Fun huh?

[Jake Raby]

Split it first...

If it consumes the lifter or lobe, it will "Extrude hone" all the oil galleys, pass through the filter and commence to munch your bearings...

If you feel this is it, split it now. After it fails, you may lose a whole lot of other parts that are in perfect shape right now.

If it were mine, it would be apart tonite.

[norustscott]

http://photos.yahoo.com/bc/lsg914


Pictures of the suspected bad lifter...and proposed USED replacement.

Jake, Don't get me wrong. I fully understand the ramifications of the replacement. There is a chance that it will work. I do appreciate your sharing your expertice and experience. Without it we as a group would be in less informed. Look on the bright side. Possible order in about three months...

this weekend will be time to roll the dice. More to follow...

lsg

[Jake Raby]

That looks like a great candidate to me.......you won't know till you try it. Good luck Man!

[evill]

Have you considered that it might be the pushrod? You can measure them cold, I would measure all of them, then heat them in an oven and remeasure when hot to be sure that one (or more) rods do not have an increased rate of thermal expansion than the others.

Ed

[norustscott]

Thought of it. Discounted it because even after the pushrod/engine cools down the valve clearence is still zero on that valve. I figure the push rod may expand too much but it won't stay that way after the cool down. Also the clearence problems surfaces after several heat cycles and roughly 175 miles. BTW. I will be replacing the pushrod anyway.

[Tom Perso]

Scott,

Does the cup move up and down inside of the bad lifter? I had a set of Scat 2-piece lifters that my webcam ate for lunch. Here's what they look like....



Here's what it looks like apart.




Here's what the face looked like after 1 hour of run time.



Jake's right, a cam does NOT play around. There's not much choice you've got in the ordeal. Fill the crankcase with the highest zinc content oil you can get (Try some diesel oil) and cross your fingers. We are all pulling for you...

Oh, I got side-tracked. Why I asked about the lifter was the 2-piece one I had, the cup could move up and down in it. It wasn't hydraulic, but if enough oil pressure got up in there, *MAYBE* and that is a big-@ssed maybe, it could expand and essentially make the effective pushrod length longer. Hmmm.... But, you say it still stayed tight after it was shut off. How weird.

I'm stumped.

Later,
Tom

[norustscott]

Even the stock lifter is a two piece unit. The cup that comes into contact with the push rod is a seperate piece.v Here is how I know.


I took mesurements of the problem lifter from the edge of the push rod side of the lifter see A...to the inner cup landing. the ledge next to the wall of the outer lifter See B.

I quadrand off the lifter and took four measurements


I .412"
II .408
III .410
IV .410"

Average .410"


Next I took an old push rod, placed it into the cup of the lifter. Held it vertical and gave the push rod three sharp raps with a small ball peen hammer.

I repeated the measurement process.


I .421"
II .420"
III .420"
IV .421"

Average .4205

In short the lifter "grows" .0105" in a single "Cycle" See below for cycle definition. Based on this cycle concept, If I simply corrected the clearence without seating the inner cup, it would continue to add .010" or less, with each cylce. Only to eventually have it drop adn give me .020"( funny huh...drop and give me twenty?)


My theory is that during operation the inner cup of the lifter becomes loose with Oil pressure quickly taking up the .006" clearence at the adjuster. The cup is wegded in place by the next lift of the cam.

Keep in mind are would go through three or four of these cylces with the valve clearence going away each time only to suddenly have a loose valve, .020" and a lot of noise. I cannot explain how maybe 40psi can compress the valve spring to hold the valve slightly open, but it does. I have witnessed it since October 2002.

This last time I stopped the engine immediatly after seeing symptoms. Took out the lifter and started the process above.

If this is the real problem, should I consider trying to weld the inner cup to the outer portionof the lifter? Peen material to keep it from moving? This would solve my "new" lifter problem.

as always, bring on the comments...


Scott

[Tom Perso]

Welding might be difficult in that tight area, plus the heat could distort the lifter "roundness". I'd try peening the area first.

That is soooo weird though, man - you have done your homework. I never knew the stock lifter was two-piece, it looks like your lifter is very similar to my Webcam lifter.

I'd try peening it first, then replacing it with another lifter and hope the cam stays where it's supposed to.

Beyond that, all I can say is split the case and install new cam and lifters from Webcam.

But, if you're going to split the case, it seems like an oppurtune time to install a stroker cranksh.... Ahhh, nevermind... I'll get you into trouble.

Later,
Tom

[Jake Raby]

This is interesting...

The stock lifter is a 2 piece design.. You could try several means of peening, but it will always be in your mind that there is an issue with the engine. If you drive the car daily, like I drive mine, and depend on it for long trips, thats a scary thing.

I still say split the case.....

[tryan]

the surface hardness of the cam and lifter MUST be the same. take your bad lifter, the 'new' one and another from your existing vavle train to a plating company or machine shop.

the bad lifter will be soft. check the hardness the new one against an existing good one.

[Jake Raby]

Like I said....

Split the case. replace the set with Web units and just drive.

If you do a sanitary job of it and have a good engine stand you can get by with only reoving the rocker arms from teh 3-4 side. Carefully disassemble the 1-2 side and bag everything, leave the cylinders and pistons loaded, and slide out the pins.

This way you can tilt the engine up, placing the 3-4 side down and split the case, remove the cam ane replace it.

I do this all the time with test engines, just make sure all surfaces are clean when you reseal it all.


If the cam and lifters munch, you will not have life this easy. Instead of taking a day to do, it will take a week!