Vilhuer

While down there, replace round rubber seal at top of oil suction tube. Its only $6.

jcorenman

MrMerlin raised an interesting point on the other site-- that absent any metal in the drained oil or any knocking noises from the bottom end, that it might be best to leave the bearings alone.

We changed motor mounts and the pan gasket on the GT last year (Nov 08 actually), and I thought about bearings but decided to leave them alone. At that time they had 151K miles (now 172) and the history was relatively unknown, which would indicate caution. But the sump magnet was clean, nothing in the filter, and an oil analysis came back clean-- lead and copper were 8 and 7 ppm respectively (miles on oil unknown), which is in line with what Doug Hillary has written here. So I left them alone, and continue to get an oil analysis (Blackstone) when the oil is changed-- so far, no changes.

The downside to changing bearings is getting the bearings and clearances right. My understanding is that the Glyco's are softer and tighter, which doesn't seem like a good tradeoff over stock bearings in good condition. Porsche OE bearings come in different size groups and some mix-and-match can be used to set clearance, if the engine is disassembled. Plastigauge provides a rough indicator of clearance, but not as good as a micrometer. And the WYAIT argument isn't very compelling, a few hours work to get the pan off isn't that big a deal in the context of bearing issues.

Which all suggests, to me, that the best option might be to wait for some signs of ill health and then do a general engine refresh.

Am I kidding myself that an oil analysis would provide ample warning of an unhappy bearing?

AO

I have to disagree with Jim to some extent. When they are "right there" it only take a minute to check the bearings. If they look good, putting them back status quo should have no effect. This is the quickest way to see if there is any undue wear.

Now if there is some wear, then replacement becomes a topic for wide discussion. I only found out afterward I had replaced mine that there were different tollerance groups, etc. Man I think I got very lucky. I was like a bull in a china shop. Better lucky than good, I guess. Could have been a very expensive education.

dcrasta

I dont think your 'kidding yourself' ..I think you have the more sensible approach. I would not replace rod bearings without evidence of them needing replacement. Oil analysis can tell you alot about the condition of all the bearings, (rod/crank) without having to 'break the seal' Something like Rod bearings, done wrong, can create a problem where non existed before. To the OP, I would suggest a similar approach, some Oil analysis before deciding to inspect or replace the bearings.

GregBBRD

What harm is there in looking at #2 and #6? Just keep the bearings in the original positions. Use new nuts. The torque angle specification is calculated using new nuts. Used nuts torque too high and might stretch the rod bolts too far.

The rod bearing thing has been discussed a zillion times. Use factory bearings. Blue is the tightest, yellow is the middle clearance and red is the loose bearing. The bearings generally come two in a package...usually one red and one blue....although sometimes you will get two yellows. Never seen any other combinations. Generally the cranks do not wear very much and the blue bearings are too tight...especially for these two cylinders. I'd measure the crank and see where it falls in the specifications. If it is on the "big" end of specification (most are) I'd either use two reds or two yellows on these cylinders. You might end up with "extra" rod bearings...as you might have to buy two sets to get two red bearings...but this is worth the extra cost. I save the blue bearings for a crank that has been micropolished a bit too far...otherwise they are just about useless. Generally all the Glyco bearings will measure the same as "blue" bearings. Glyco assumes that all of their replacement bearings are going into used engines (good assumption) and that there is always a bit of crank wear (bad assumption), so they provide "tight" bearings.

AO

Eaxctly my thoughts.

9x8

Checked the second one - since it should have had the most wear of all.
Based on what I saw, 240K Km is nothing for this engine.

It deffo has some wear, but should be good for another 100K Kms.

BC

Last time I was checking rod bearing clearances on Glycos after you started talking about them - On a mock engine - I had several rod bolts stretch past yield. About half.

I know alot of people who have gone in an replaced the rod bearings a couple times at least - what about the rod bolts? Don't they have an end-life? I know the new nuts thing - but what I found scared me from thinking its just as easy as replacing the bearings on demand.

BC

And if the rod bolts stretch while you are just in there, then that means everything comes out.

And if the rod bolts are replaced, then the big end needs to be resized, from what I have read.

dr bob

BC, almost forur years between installing the bearings and deciding on the bolts?

BC

Eye-toll ya I work SLOW.

Just kidding. Different engine. I was just double checking something for my rat motor.

Nuts have been ordered from 928intl for this one. Just was hoping to get stuff together this weekend. I will torque on these nuts to spec the bearing clearances, assemble the short block and then use new nuts and torque them once later.