Inspect 2/6 rod bearings with TB off and crank locked at 45░ BTDC - Rennlist Discussion Forums



Inspect 2/6 rod bearings with TB off and crank locked at 45░ BTDC

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Old 03-13-2017, 07:18 PM   #1
skpyle
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Default Inspect 2/6 rod bearings with TB off and crank locked at 45░ BTDC

Hello Gentlemen,

In the very near future, I am replacing the motor mounts and installing a silicone oil pan gasket on the Red Witch. Due to a minor scare with a slight metallic sheen in the drained oil, I am inspecting #2 and #6 rod bearings.

As of right now, the timing belt is off and the crankshaft is locked at 45░ BTDC. Will I be able to access #2 and #6 rod caps to remove them with the crank in this position?

If not, can I turn each cam to TDC then turn and lock the crank to TDC for better access?
Or, do I need to wait until I have the timing belt back on?

This is my first time into the crankcase on a 928. I have already ordered 4 new rod cap nuts.


Thanks for any and all advice!
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Old 03-13-2017, 07:35 PM   #2
Rob Edwards
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Get the timing belt back on first, so crank and cam are talking to each other.
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Old 03-13-2017, 08:21 PM   #3
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Hi Rob!
Thanks for the advice. That makes sense. I am now in the process of reading through a bunch of threads on rod bearings. I have come across numerous posts by yourself and Greg Brown.

I was going to check only #'s 2 and 6. That is a bad idea. I am now checking all 8 sets of rod bearings. I have just ordered 12 more rod nuts. And hope like h*ll that I don't need to replace the rod bearings. From what I understand from reading Greg's posts, it is a crap shoot getting the appropriate size bearing shells unless you are willing to buy 20-some-odd sets of bearings.

I will reinstall the timing components then tackle the rod bearings.

Thanks!
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Old 03-13-2017, 08:29 PM   #4
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If the crank is at 45 you can rotate the crankshaft as much as your heart desires. That's why some put it at 45 instead of TDC.
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Old 03-13-2017, 09:04 PM   #5
M. Requin
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I don't recall that you have mentioned doing this, but if not, my first move would be to send an oil sample to Blackstone for analysis, before I undertook more drastic operations.
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Old 03-13-2017, 09:24 PM   #6
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Quote:
Originally Posted by SeanR View Post
If the crank is at 45 you can rotate the crankshaft as much as your heart desires. That's why some put it at 45 instead of TDC.
SeanR, I don't mean to be dense, but do you mean if both cams are at 45░, I can rotate the crank all I want, or if the crank is at 45░ I can rotate the cams all I want?



Quote:
Originally Posted by M. Requin View Post
I don't recall that you have mentioned doing this, but if not, my first move would be to send an oil sample to Blackstone for analysis, before I undertook more drastic operations.
Martin, it was too late. The two drain pans I used to catch the oil from my 928 are the same drain pans I use for everything else. So, they are not clean and the 928 oil is contaminated. I did not see the ever so slight metallic sheen until the oil was drained.
I did catch a small amount of oil from the oil filter, but I do not think it is enough to send in for a sample.
Assuming I find nothing that causes me to stab myself in the heart with a screwdriver, I plan on reassembling everything and driving it. After 5000 miles, send an oil sample off and cut open the oil filter again.
I don't consider checking the rod bearings to be drastic, since I am already going to be in there replacing the oil pan gasket.



Thanks!
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Old 03-13-2017, 10:21 PM   #7
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Seth - are you ever going to drive that dang thing!
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Old 03-13-2017, 10:32 PM   #8
Rob Edwards
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If the crank is at 45ᵒ BTDC, you can spin the cams as much as you want.

Imagine looking at the engine from the front, in the car. If the crank is at #1 TDC, the 1-5 rod journal is closest to the bottom of cylinder 1, pointing at 10:30, and the 2/6 journal is over at 1:30. At 45 degrees BTDC, the 1-5 is at 9 o'clock, and the 2/6 journal is at 12:00. For you to be able to change the 2-6 rod bearings, you want that journal at the bottom of the motor, or 6 oclock. So the crank will have to be 135 degrees ATDC #1.

If you took the belt off at 45 BTDC #1 or at TDC #1, you have to rotate the crank 180 or 135 degrees to get the 2-6 to the bottom of the engine. I wouldn't do that with the TB off.

And you'll want the freedom of rotating the crank so it's a straight shot at properly torquing the rod bolts, so install the belt.

Last edited by Rob Edwards; 03-14-2017 at 01:13 PM.
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Old 03-13-2017, 10:38 PM   #9
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Yea. I mistyped that. Sorry.
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Old 03-14-2017, 02:37 AM   #10
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Seth,

Your enthusiasm is without question but I wonder if it is not clouding your judgement. If you do have a problem with the plain bearings how would you know it is big ends and not the mains [or something else for that matter]?

Would it not make more sense to flush your motor with the good Doctors' favourite brew [Swepco 502] or Rislone, stick in some fresh oil and then after running it some and assuming no other negative signs, send the oil away for anyalysis after say 5000 miles to a lab as some of our friends do regularly?

On the other hand supposing you do find a suspect bearing what next? Would you take the motor apart yourself, do further analysis to see why it failed or replace the suspect bearing you found knowing that others might have an issue?

If a bearing is in the process of failing the question would be why? Not saying it cannot or will not happen, especially if your PO has done something silly like run with too little oil in the sump or inadequate oil, but sooner or later you should see more tell tale signs like uncharacteristic oil pressure indications.

Whether the brains trust would agree I do not know but my [limited ] experience of shell bearing failure [on furend's motors] is that once it happens there is little doubt that a bearing has wiped. Your call of course but do make sure you are not "knee jerking" before you dive into something major like this. At the very least build a consensus that your course of action is appropriate.

Either way good luck- hopefully it will be something and nothing.

Rgds

Fred
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Old 03-14-2017, 01:08 PM   #11
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Quote:
Originally Posted by FredR View Post
Seth,

Your enthusiasm is without question but I wonder if it is not clouding your judgement. If you do have a problem with the plain bearings how would you know it is big ends and not the mains [or something else for that matter]?

Would it not make more sense to flush your motor with the good Doctors' favourite brew [Swepco 502] or Rislone, stick in some fresh oil and then after running it some and assuming no other negative signs, send the oil away for anyalysis after say 5000 miles to a lab as some of our friends do regularly?

On the other hand supposing you do find a suspect bearing what next? Would you take the motor apart yourself, do further analysis to see why it failed or replace the suspect bearing you found knowing that others might have an issue?

If a bearing is in the process of failing the question would be why? Not saying it cannot or will not happen, especially if your PO has done something silly like run with too little oil in the sump or inadequate oil, but sooner or later you should see more tell tale signs like uncharacteristic oil pressure indications.

Whether the brains trust would agree I do not know but my [limited ] experience of shell bearing failure [on furend's motors] is that once it happens there is little doubt that a bearing has wiped. Your call of course but do make sure you are not "knee jerking" before you dive into something major like this. At the very least build a consensus that your course of action is appropriate.

Either way good luck- hopefully it will be something and nothing.

Rgds

Fred
While it is difficult to tell the condition of the main bearings by looking at the rod bearings, the rod bearings can reveal some information.

Therefore, individually checking the rod bearings is always a good idea on high mileage engines....and the amount of effort is minimal.

If they look good, clean them, re-oil them, and re-install them. If they have wear, replace them with the same size bearing. If they are badly damaged, pull the cradle and look at the main bearings.

Note that the loads on the stock 4.5 liter and 4.7 liter rod bearings are very low. Additionally, since these engines do not stuff as much oil up into the cylinder heads when running, nor use much oil, it is rare for the oil pick-up to be uncovered. Rod bearings, on these engines, should be (and generally are) extremely nice.
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Old 03-14-2017, 01:24 PM   #12
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Quote:
Originally Posted by linderpat View Post
Seth - are you ever going to drive that dang thing!
(hangs head in shame) Ed, I have fallen off the WYAIT cliff and hope to hit bottom sooner or later. I bought this car as a driver, but kept finding more and more little things wrong. This bloomed into a nasty WYAIT tree. I hate that I have gone too far, but I am glad that I am fixing all these issues. I had planned on them sooner or later. Now they are all getting done now.




Quote:
Originally Posted by Rob Edwards View Post
If the crank is at 45o BTDC, you can spin the cams as much as you want.

Imagine looking at the engine from the front, in the car. If the crank is at #1 TDC, the 1-5 rod journal is closest to the bottom of cylinder 1, pointing at 10:30, and the 2/6 journal is over at 1:30. At 45 degrees BTDC, the 1-5 is at 9 o'clock, and the 2/6 journal is at 12:00. For you to be able to change the 2-6 rod bearings, you want that journal at the bottom of the motor, or 6 oclock. So the crank will have to be 135 degrees ATDC #1.

If you took the belt off at 45 BTDC #1 or at TDC #1, you have to rotate the crank 180 or 135 degrees to get the 2-6 to the bottom of the engine. I wouldn't do that with the TB off.

And you'll want the freedom of rotating the crank so it's a straight shot at properly torquing the rod bolts, so install the belt.
Rob, that makes perfect sense. Thank you. I will reinstall the timing belt system then go on to the rod caps.




Quote:
Originally Posted by SeanR View Post
Yea. I mistyped that. Sorry.
Thanks Sean!





Quote:
Originally Posted by FredR View Post
Seth,

Your enthusiasm is without question but I wonder if it is not clouding your judgement. If you do have a problem with the plain bearings how would you know it is big ends and not the mains [or something else for that matter]?

Would it not make more sense to flush your motor with the good Doctors' favourite brew [Swepco 502] or Rislone, stick in some fresh oil and then after running it some and assuming no other negative signs, send the oil away for anyalysis after say 5000 miles to a lab as some of our friends do regularly?

On the other hand supposing you do find a suspect bearing what next? Would you take the motor apart yourself, do further analysis to see why it failed or replace the suspect bearing you found knowing that others might have an issue?

If a bearing is in the process of failing the question would be why? Not saying it cannot or will not happen, especially if your PO has done something silly like run with too little oil in the sump or inadequate oil, but sooner or later you should see more tell tale signs like uncharacteristic oil pressure indications.

Whether the brains trust would agree I do not know but my [limited ] experience of shell bearing failure [on furend's motors] is that once it happens there is little doubt that a bearing has wiped. Your call of course but do make sure you are not "knee jerking" before you dive into something major like this. At the very least build a consensus that your course of action is appropriate.

Either way good luck- hopefully it will be something and nothing.

Rgds

Fred

Fred, you bring up some very good points. All I can respond with is if I don't check, I'll never know. I am going on a touch of paranoia, and alot of faith in what I have read here on Rennlist over the past few years.

To my understanding, the crank, mains, and rods bearings are quite robust. They only wear heavily or fail under extraoridinary circumstances. To my knowledge, my car has never been tracked, abused, or run low on oil. The PO is human, but has proven to have loved this car and shoveled money into it during his tenure. I am inclined to think he didn't abuse it.
I don't think there is TBF, as the shop checked crank play. It was spot on, and nobody has been in there in 20 years or so.
Oil pressure has always been good, gauge pegged at start or when running, and always high otherwise. However, the shop installed a new oil pump as part of the recommissioning repairs and such.

So, I don't THINK a bearing is failing, but I want to check as best as I can.

Give me a moment and I will explain why I am doing all this.

To be honest, I had not thought about flushing the engine. That is definitely worth doing once I get her back together and running.

As far as what do I do if I find a failed bearing? That is easy. Burn the Red Witch to the ground followed by me committing seppuku.
Why? Because I am at the end of my resources. I have blown my wad to get to the point I am at now. I have just about everything I need to turn the Red Witch into a sweet daily driver. Any major failure puts a stop to this process. A failed bearing is a major failure. The Red Witch becomes a garage ornament for however long it takes me to build up resources again.
It is what it is. My own fault.
Having said that, that is why I need to know what the rod bearings look like.

Assuming the worst, I would fix it myself. Depending upon the damage, I might go the used engine route. Either way, it would bloom into a refresh that included the head gaskets and a valve job. That would just take quite a bit of time. And money.

I have killed a few engines, and built a few engines. I have seen a few sets of worn and wiped bearings. I don't profess to be an expert. However, I can recognize debris in the sump, and scored crankshaft journals.
My intent is to remove the rod caps and document all I see.


For those of you still reading, here is why I am pulling the rod caps:

While draining the engine oil in preparation for pulling the oil pan, I saw a slight metallic sheen in the oil in the sunlight. That scared the sh*t outta me. In my mind, I should not see any sheen. However, it was only a slight sheen, and could only be seen in sunlight or strong light. It did not look like the pan of gold from the gentleman who recently bought the S3 with the failed bearings.
There was nothing on the end of the magnetic drain plug.
I cut apart the oil filter and found only two things: a tiny blop of something that looked and smeared like silver antisieze and a tiny sliver of metal. Using a magnifying glass and strong light, I saw no metallic particulate matter in the filter media, on either side.
I cannot use the drained oil for a sample, as it did not go into a clean drain pan. I did save a small amount of oil from the filter, but I don't think it is enough to send off for analysis. If you shine a strong light into this little bit of oil, you can see a fine metallic sheen.

I know I cannot check the main bearings. Unless the failure of them was massive, it would not be obvious. I can check the rod bearings. As well, I can see what kind of debris is in the sump. If I don't check, I'll never know.
As well, since the oil pan is going to be off to replace the gasket, there is pretty much no better time to check the rod bearings. I have decent torque wrenches and the knowledge on how to use them.

My intent is to button everything back up and drive her. At 5000 miles, a sample of oil will be sent off for analysis and the oil filter will be cut apart for inspection.

Fred alluded to my enthusiasm clouding my judgement. That is always a possibility. In this case, add in a smattering of paranoia. I need to know what the bearings look like because I saw a metallic sheen.
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Old 03-14-2017, 01:28 PM   #13
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Quote:
Originally Posted by GregBBRD View Post
While it is difficult to tell the condition of the main bearings by looking at the rod bearings, the rod bearings can reveal some information.

Therefore, individually checking the rod bearings is always a good idea on high mileage engines....and the amount of effort is minimal.

If they look good, clean them, re-oil them, and re-install them. If they have wear, replace them with the same size bearing. If they are badly damaged, pull the cradle and look at the main bearings.

Note that the loads on the stock 4.5 liter and 4.7 liter rod bearings are very low. Additionally, since these engines do not stuff as much oil up into the cylinder heads when running, nor use much oil, it is rare for the oil pick-up to be uncovered. Rod bearings, on these engines, should be (and generally are) extremely nice.

Thanks, Greg!

The Red Witch has around 165,000 on her clock. Broken in but not worn out. I think that is high enough mileage to justify checking the rods. A general theme I have picked up from yours and other posts on bearings in a 928 is that if the rod bearings are OK, then the main bearings are likely OK. Though not always. In some of your threads on failing harmonic balancers, you had noted failures of main bearings while the rods looked good.

I am just going to have to hope for the best.
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Old 03-14-2017, 02:43 PM   #14
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Seth,

If you still have the oil why not send it off for a full lab analysis to confirm whether or not you are actually seeing anything worth seeing. If you had a thrust bearing issue crank end float would be the indicator but I seem to remember you have eliminated that.

You may have an issue developing but surely it is worth taking steps to affirm such before diving into the motor? Even if you jump into this do you have someone reliable who can help you analyse what you actually see if you do pull the big ends?

Rgds

Fred
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Old 03-14-2017, 02:56 PM   #15
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Hi Fred!

I have just checked Blackstone Labs' website. They need at least 2.5oz of oil for a sample. I don't have that much of the old oil.

I will have to wait for the next oil change.

As for the rod bearings, my intent is to post photographs of each individual bearing shell and go from there. I should be able to recognize massive failure. I will rely on Rennlist for interpretation of the finer nuances.
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