Benton

Please Note: I am trying to determine the variance in thickness of the Genuine Porsche rod bearing shells and the Glyco rod bearing shells, as well as the consistency (or lack thereof) in Glyco rod bearings. I realize the important factor for engine building is the bearing clearance, but that figure and measuring it are not the main purpose of this discussion.

For those of you who have access to the correct measuring devices, what is your experience measuring the thickness of rod bearing shells? I have not been able to locate this information here or on the 944 boards, other than a few folks that measured one with a caliper at the edge (won't trust that one).

I borrowed a Ball-Anvil micrometer w/ ratchet stop (ball top, flat anvil) from the shop next door to measure my set of 16 Glyco bearing halves. I am unsure if this micrometer is within spec (should be), so I would love to compare these numbers. All shells were measured as close as possible to the center, all measured several times for repeatable results. On the final digit, some shells seemed to want to creep to a larger number, some smaller, but the numbers shown are what was achieved repeatedly.

They were as follows:

13 halves @ .05880"
3 halves @ .05875"

Given that these numbers are pretty consistent, does the variance in clearance from Glyco to Genuine Porsche come from another factor such as a slightly different length of the shell (thus "squishing" into the rod journal more/less) or something else? Trying to assist those, like myself, that can only afford to rebuild an engine if it is DIY, but want to do it correctly.

IcemanG17

Did you measure any Porsche bearings?

When I pulled the 2-6 from my 117k 84 engine we used a not super precise micrometer and both bearings were in the high .057 to very low .058 range

Rob Edwards

I measured a quartet of Porsche 'yellow' bearings with a ball mic; all were 0.0591" thick and all are now on my 2-6 journal in the GT.

davek9

I'll be doing this tomorrow night, have both types Porsche standard "green" and Glyco will post what we measure.

Benton

Brian-
No, I do not have any new Porsche bearings. However, I have one engine that was in the race car with 2-season-old Glycos that I intend to measure and report, as well as a set of used original bearings from a 58,000 mile engine that may end up being the one that goes into the race car. I'll measure those one I have them out as well.

Rob, thanks for the info, and I look forward to your findings, Dave. Are you building an 85-86 engine or just replacing rod bearings?

GregBBRD

You are doing fine. Your measurements are a couple of tenths "tighter" than the Glycos I have here. You really need to get some factory bearings to compare.

Any measurement that I would provide would be from my own measuring tools...which are bound to vary from yours....thus pretty worthless.

davek9

The all Glyco standard and Porsche green standard all measured .059, if you round your numbers up yours will too.

you wrote: "They were as follows: 13 halves @ .05880", 3 halves @ .05875".

These matched what came out (all w/in .059) he used a small ratcheting ball mic; I'll upload some pics later on.

We replaced them all with .059, what's the point of taking the measurement out to that extreme?

IcemanG17

this is great data.......granted my example was from higher mileage stock engines with probably original rod bearings...however they looked GREAT...barely worn at all (same for crank)..... The 79 engine I sold had even better rod bearings (visual), but we didn't measure those.....

GregBBRD

Rounding cranks, rods, and bearings off to .001" is about as useful as measuring them with a 6" ruler.

Bearing clearance is important down to tenths of thousanths. If you have two bearings that are .0005" tighter, you just lost .001" of oil clearance. When you are dealing with "oil clearances" of .002", a .001 change is very significant....it's half as much clearance....and the engine will go "boom".

Jim @ EuroWerks

There are more people watching 928 stuff than any other place on rennlist! You people are crazy!

Let me help you guys catch up to the 911 guys. Glyco changed there bearing make up years ago. They started making a bi metal bearing instead of a tri metal bearing. If you are building a stock 911 these bearings will do. If you are building something with guts, you need to look around. The only reason the factory bearings might be better is they may have been in stock for a long time and may be of good old school technology.

atb

Jim,

The issue with the bearings is that the Glyco's tend to be a tighter fit, too tight based on some people's experiences, whereas the factory bearings hold proper tolerance. I think the issue is more about the physical spec of the bearing, not the material they are made out of.

GregBBRD

I would have to agree. i used to think that the "factory" rod bearings were different that the Glyco replacements, in terms of construction, but the weights of the pieces would indicate that they are the same. They weigh so close to exactly the same that it would be difficult to believe they are different.

Tom. M

Interesting... I spent a couple hours at the shop and was taught the finer parts of using a ball/anvil micrometer by Adam (ATB).....

Grabbed the glyco's and measured them.
My results are the same as Benton's
14 out of the 16 measured:
0.05875"

One measured 0.05880
One measured 0.05870

I went back and double checked those two and after a couple tries was able to get 0.05875" consistently.

There is definitely a technique to getting the proper measurement off of the ball anvil micrometer.

I pulled the #2 bearings and checked those, and they both (top and bottom) spec'd at 0.05875"... so good to go..

Pulled the #6 bearings and the bottom came in at 0.05880" . I loaded up the glyco's and was planning on plastigauging to see what the clearance was, but didn't have any good pieces left..so I'll have to hit the parts store to grab some more and check.

Hope to get back to it next weekend and hope the rest of the bearings fall in line

Just happy to see similar measurement by others...BTW..this ball/anvil micrometer wasn't a high dollar one.. just the basic online micrometer .....so I am surprised my numbers came out the same as Benton's..