996 Lifters: Recommended Testing / Assembly Procedure?

[hankster66]

I'm doing a top-end refresh on my 2000 C2 as part of IMSB and timing correction. Looking for advice on how to evaluate / treat the lifters.

 

Background...

When I inspected the lifters, all look good cosmetically. When they came out of their cradle, they all were stiff as you would expect, except for one or two, but generally not squishy. At first, doing this for the first time, I thought that was a bad thing until reading up on it. As I understand it now, they should be stiff coming out of the engine and weep over time when outside of a pressurized environment. So when they remained "stuck" after being out for 2 weeks while I worked other items, I began to wonder if they were that way for all the wrong reasons. I worked them over a couple of days while I did other work, getting the old oil (very dirty) out of them. I gave them a hot bath in engine oil as some threads suggested to get the air out of them and to replenish with new oil. I was worried after a day that I should have left well enough alone as they were all still very pliable, so I did a repeat hot soak (forgive my novice terminology), depressing them each several times. After another 24 hours there's a huge noticeable difference. They're still not quite there yet, but maybe it's just a matter of time. The idea being if any cannot accept/retain the new oil, I'll replace them. I know that once in the car, if not damaged, they'll regain their appropriate state, but I want to make sure before they go back in that they have a likelihood of doing so.

 

Questions...
How long does it normally take for them to be soaking in oil before I can properly check them?
How much play should they have / not have?
If for argument sake, one or two are bad, do I need to replace the entire bank of them, all 4 associated with the respective cylinder, or just the bad one?

I found the OEM INAs on eEuroparts for 16.97ea. roughly $400 for all 24, which isn't bad, but I'm trying to keep costs down on this project (without doing something stupid along the way).

[JFP in PA]

These lifters have problems because of their design, which allows crud to accumulate inside their internal oil passages.  How long they need to soak is totally dependent on how badly they are fouled.

 

Normally, if we get a couple of bad units, we just replace them all with new.

[hankster66]

9 hours ago, JFP in PA said:

These lifters have problems because of their design, which allows crud to accumulate inside their internal oil passages.  How long they need to soak is totally dependent on how badly they are fouled.

 

Normally, if we get a couple of bad units, we just replace them all with new.

 

Thanks. I'm seriously considering that route.

 

Because I'm in wait mode (other parts / soaking bank 1), is it ok to open up bank 2 while bank 1 is open to do timing / refresh items, or is it best to have one side done before getting to work on the other side? I also have the water pump and oil drive / valve upgrade and just wondering about the best work sequence. I am assuming it's best to do the IMSB after I have everything timed as well. Thoughts?

[JFP in PA]

I will assume, for the sake of argument, that the engine is out of the car, which makes all of this one Hell of lot easier.

 

Yes, you can do both banks at the same time; this is the normal process in a from scratch engine assembly process, only you are doing it in reverse.  Where people tend to go wrong is when they hand rotated the engine with one or more banks completely out of cam allocation, not knowing you can actually damage valves doing that.

 

As for the IMS, once you have the cam allocations completed on both banks, you need to lock the engine at TDC, and lock the cams, before proceeding.

[hankster66]

2 hours ago, JFP in PA said:

I will assume, for the sake of argument, that the engine is out of the car, which makes all of this one Hell of lot easier.

 

Yes, you can do both banks at the same time; this is the normal process in a from scratch engine assembly process, only you are doing it in reverse.  Where people tend to go wrong is when they hand rotated the engine with one or more banks completely out of cam allocation, not knowing you can actually damage valves doing that.

 

As for the IMS, once you have the cam allocations completed on both banks, you need to lock the engine at TDC, and lock the cams, before proceeding.

Great... and yes, engine out. Can't imagine doing this work otherwise, at least with my abilities. And I understand need to lock TDC and cams for IMSB.

 

To be clear about concern for potential valve damage when rotating engine by hand, I am understanding that to mean that when I set timing on one side, I need to have the cams on the other side in place, possibly with cover on as well to make sure engine components are moving in their natural state... do I have the right? (I have a 5-chain engine.)

[JFP in PA]

Yes, but you do not have to have the cam covers on if you use the correct tooling to hold the cams in place with the covers off:

[hankster66]

As a follow-up. I replaced all the lifters, set both banks timing as instructed. Confirmed respective cam notches and lobes are pointing appropriately at TDC... Everything looks good. My main concern now is if there is a simple way for me to validate that everything is operating properly. I tried to do a leak-down test (as that's what I have) but seem to get considerable air coming out of exhaust. I knew I would get more air escaping than when I did the test before disassembly because of lack of oil, etc. but not as much as I'm noticing. The only thing I can think of is that lifters may have leaked and will not "set" completely until engine is running. I just want to eliminate any potential mistakes I may have made.

 

 

[JFP in PA]

Make sure whichever cylinder is leaking air out the exhaust is at TDC before plugging in the leak down unit.  

[hankster66]

Yes, checked twice and rotated additional 180 degrees. Same issue on bank 2. The valves are visually closed, but obviously not entirely sealed. I had checked leakage before tear down on all cylinders; no issues. to confirm, doing this with cam cover offer, with cam tools in place.

[JFP in PA]

26 minutes ago, hankster66 said:

Yes, checked twice and rotated additional 180 degrees. Same issue on bank 2. The valves are visually closed, but obviously not entirely sealed. I had checked leakage before tear down on all cylinders; no issues. to confirm, doing this with cam cover offer, with cam tools in place.

 

If it were in my shop, I would borescope the questionable cylinders to look at the valves.  Only real probabilities here are bad valves (burnt or hung open), and if confirmed by inspection or checking valve heights when closed, the heads will probably have to come off.

[hankster66]

7 minutes ago, JFP in PA said:

 

If it were in my shop, I would borescope the questionable cylinders to look at the valves.  Only real probabilities here are bad valves (burnt or hung open), and if confirmed by inspection or checking valve heights when closed, the heads will probably have to come off.

Isn't it odd though that multiple cylinders are leaking when there were no issues prior to disassembly. Assuming they're not burnt, I can see how something in the assembly process has hung them open, but again odd (although this is new to me) that multiple cylinders would be experiencing the same problem that was not pre-existing.

 

If issue is hung open, is the only remedy taking the heads off?

[JFP in PA]

9 minutes ago, hankster66 said:

Isn't it odd though that multiple cylinders are leaking when there were no issues prior to disassembly. Assuming they're not burnt, I can see how something in the assembly process has hung them open, but again odd (although this is new to me) that multiple cylinders would be experiencing the same problem that was not pre-existing.

 

If issue is hung open, is the only remedy taking the heads off?

 

There is one thing in doing work on these engines that can result in valve problems: Rotating the engine, even by hand, in the opposite direction to how it runs.  Everyone thinks that if they are trying to rotate the engine to say TDC and overshoot, you can simply rotate it in the other direction.  Problem is that you should never rotate the M96/97 engines backwards as this can cause slight piston to valve contact issues, and leaking valves.  The reason I would drop an inspection camera into the bore is to look for marks on the pistons, which indicate contact has occurred. 

 

There are a limited number of ways a valve can leak; burnt (the mating surface is burned away), valve head is bent and will not correctly seat, and valve stem is bent, which jams the stem in the guide, holding the valve off the seat. That is why I suggested checking the valve installed height on the affected cylinders; if the stem is jammed in the guide, the installed height will be lower than the rest.  This can also be the case if a spring has failed (broken), which will have the same impact, the installed height would be off to the low side.

 

If it is a spring, it is possible to fix it without removing the heads, if it is any of the other candidates, you have no other choice as it would be impossible to fix with the head in place.  I'm sure this is not what you wanted to hear, but it is the case.

[hankster66]

Thanks JFP. To confirm if there was piston impact, below are pictures, two for each cylinder in order from 1-6.

 

[JFP in PA]

I do not see any obvious signs of mechanical contact.

[hankster66]

1 hour ago, JFP in PA said:

I do not see any obvious signs of mechanical contact.

Thanks for taking a look. So I guess my next move is checking installed height.

- I saw that the way to do this is with spring removed, but wouldn't measuring them in be similar or is the issue measuring from the space covered by the spring?

- As I understand I'm looking for deviations from cylinder to cylinder, but is there also standard spec or range for installed height in these engines?

- If by chance I see no deviations, I may still have to go in to resolve, but is there anything else I could have done in the assembly that might explain this?

[JFP in PA]

You can get a good idea of the installed heights by measuring from the spring retainer to the cylinder head surface with everything assembled.  It is not as accurate as doing it disassembled, but you are looking for an outlier rather than small incremental differences.  Sometimes you can actually see that one or more looks "different" than the others without even using a measuring tool. Installed height is determined by target valve seat pressures, but tends to be around 1.34 inches.

 

The only thing I can think of that you could have done during assembly is to miss enough of the actual valve timing that the cams are holding valves slightly open that should be closed at TDC.

[hankster66]

On 7/15/2022 at 8:53 AM, JFP in PA said:

The only thing I can think of that you could have done during assembly is to miss enough of the actual valve timing that the cams are holding valves slightly open that should be closed at TDC.

So I disassembled both banks to measure valve install height and I noticed that on both banks I was out of time (chain link to cam mark) on both banks. I assumed that they always lined up as the cams rotated back to TDC. When I took both cams out and removed the variocam to orient the chains to the cams again, I rotated by hand to see what happened and they don't line up after multiple rotations... had not read that anywhere. On the outside, both sets of cams remained in time (cam tool slotted in perfectly).

Can you confirm what the behavior should be on the chains?

[JFP in PA]

What timing procedure did you use to initially set the cam allocations? And are you sure you did not mix the cam locations (switched the cams)?

[hankster66]

2 hours ago, JFP in PA said:

What timing procedure did you use to initially set the cam allocations? And are you sure you did not mix the cam locations (switched the cams)?

 

When installing...

- confirmed correct cam allocation

- lined up link to cam marks

- assembled vario cam / cams, and checked link and mark aligned before/after install

- put cam tools in place

- torqued down variocam and caps

- set long chain to sprocket to exhaust cam

- released variocam compression tool

- installed tensioner (pumped with oil)

- torqued down sprocket bolts

- confirmed timing marks

- rotated engine 360 at TDC

- confirmed cam timing with timing tool (but can't recall if I checked links / marks)

 

Below are pictures of cams with chain in time and then after I rotate two times until cam notch is facing up (out). Again, outside of engine, confirmed cam allocation and even double checked that the new chains were exactly same as original, and that there were six links between marking links. Is it that the cams have to rotate x times before they return to the original alignment?

 

 

[hankster66]

I attempted to spot check variation, and there appears to be some, but very difficult to confirm with springs in. Essentially, after thinking it through, I agree with you that I have to remove the heads. Even with the cams out, I'm getting air out of the exhaust, so have to resolve that.

 

In addition to my question above regarding timing, questions below about head job...

- Would you recommend I take the head to machine shop for resurfacing?

- Is there anything I should do with the head before taking it to the shop?

- Unless I find any obvious defects with guides, stems and springs, plan to reuse? Is there anything here that you would replace regardless?

- I was thinking of lapping valves myself and checking that they properly seat and measuring for installed height, etc. Seems straightforward, but your thoughts?

- Saw one of your old articles commenting on replacing head bolts. I see mixed comments and references to later 3.4 (mine is a 2000 C2) not needing to replace head bolts, especially as they don't seem to be a failure issue. I will likely be in this engine again (hopefully not to soon) to refresh the heads/rings and just wondering what I can get away with for now.

[JFP in PA]

There is only one place I would send Porsche water cooled heads: Len Hoffman   Hoffman Cylinder Heads  Len will go through them and tell you what is needed, he is one of the best in the business. 

 

If you read what I have said about bolts, you already know where I stand on this subject.  Bolts are cheap compared to having to do the job twice.

[hankster66]

On 7/18/2022 at 7:14 AM, JFP in PA said:

There is only one place I would send Porsche water cooled heads: Len Hoffman   Hoffman Cylinder Heads  Len will go through them and tell you what is needed, he is one of the best in the business. 

Thanks JFP on recommendation. Having an exchange with Len and obvious after a few exchanges why you are recommending him.

 

I was wondering before I keep going, if ok to do the IMS work now, my reasoning being if I discover issues with IMS, I may have to rethink what I'm doing with this engine. LN instructions call for locking cams presumably because most scenarios assume heads are in place. Do you see any issue with pulling and replacing IMS bearing with heads off if engine has been locked at TDC and chains are secured against the guides... or do I need to wait to have heads back on w/ cams, etc.

[JFP in PA]

You can do the IMS with the heads off; most problems that arise during DIY IMS retrofits involve the cams jumping time, which could not happen in your case.

[hankster66]

15 hours ago, JFP in PA said:

You can do the IMS with the heads off; most problems that arise during DIY IMS retrofits involve the cams jumping time, which could not happen in your case.

 

Pulled out IMSB, pics below. Everything looks like the bearing did not fail. Bearing spins, but not freely or necessarily as smoothly as it probably should. Some movement fore and aft, less so laterally. All bearings seems to be in tact, but some of the balls have loss of material, which likely explains the particulate I found inside the shaft. Curious what you think about the pitting on the inside of the flange and the black scuff marks on the out race of the bearing and inside of shaft end. It seemed to clean up nicely. Is the particulate I found normal or an indication of the bearing due for replacement?

 

 

 

[JFP in PA]

That bearing is decidedly on its way out, small amounts of ferrous particulate indicate it was already on its way to failure.  If you have not already pulled the sump cover in preparation to do the retrofit, I would do so now.  You will be looking for similar fine ferrous grit in the sump.  If you find none, you are golden, but if you find it there, it is everywhere inside the engine.