Rod Bearings Diameter Brand New 2.7

[HKZ Bob]

Hello Folks
I bought a new set of pelican rod bearings (glyco) for my 2.7 and placed them into my rods and tightened them with the specific force.

Then I gave all six rod to a automotive lab for measurement.
Here the result:

Rod 1: Pull side front : B-B 52,066 mm Pull side rear: B-B 52,064 mm
Rod 2: Pull side front : B-B 52,060 mm Pull side rear: B-B 52,054 mm
Rod 3: Pull side front : B-B 52,063 mm Pull side rear: B-B 52,060 mm
Rod 4: Pull side front : B-B 52,056 mm Pull side rear: B-B 52,053 mm
Rod 5: Pull side front : B-B 52,058 mm Pull side rear: B-B 52,058 mm
Rod 6: Pull side front : B-B 52,062 mm Pull side rear: B-B 52,060 mm


Center Value Rod 1 52,065 mm
Center Value Rod 2 52,057 mm
Center Value Rod 3 52,061 mm
Center Value Rod 4 52,054 mm
Center Value Rod 5 52,058 mm
Center Value Rod 6 52,061 mm

Waynes books says 52,020mm - 52.059 mm

So Rod 1,3,6 are out of Spec with brand new glyco bearings ?

Here the protocol




What I realized is that all values are on the upper side of the accepeted tolerance. I would like to have values in the 52.035 range.

Did you experinced the same ?
What to do in my case ?

Greetings
Bob

[356RS]

Have the rods been rebuilt and measured?

[Eagledriver]

If the rods haven't been re-machined then those numbers are pretty good. Many racers run a little on the loose side to reduce friction/power loss. If you are concerned about them then have them re-machined to the smaller end of the range.

-Andy

[gottarideduc]

HKZ,

I don't know whether your 2.7 will be stock or modified?
Rod bearings are the Achilles heel of the P engine. In our experience Glyco rod bearing quality has become a problem. We do not recommend them any more for any type of heavy use, such as sustained high RPM or high compression ratio. The factory bearings, while much pricier, are more reliable.
As to installation tolerances, eith due respect tofriction or power loss, but the most important question is: What are the oil clearances?
Make sure the rod big end is round, i.e. not more than .0005 out, then measure with bearings installed and torqued, using a bore gauge, not that spring-loaded pop-out gizmo. Compare with the crank pin diameter. Target clearance is .0025 - .0028 inches with .0030 the upper limit. Beyond that the oil pressure will drop due to too much "leakage". Match largest rod with largest pin, etc. This procedure has served well. Often, no resizing or machining of rods is necessary unless the components have seen ultra-heavy use. If new bolts are used, roundness checking is important. Curiously, sometimes new bolts make a difference, but most often they do not.
I say, IF new bolts are used. It has been our experience that the bolts in the 2.x ltr engines extremely rarely give any trouble, but 3.0 ltr on, replacement is a good idea.
I realise that this obvious disregard for absolute wear limits seems strange and simplistic, but I can only plead good success in my defense.

[HKZ Bob]

Dear All,
I used the original std rod. They were never been rebuild. Of course I used a set of used rod bolts for measurement purpose and tighten them with 50 Nm.

Eagle I am not intending my engine for race purpose but I want a good engine.

My question is do I have to worry of low oil pressure @hot, due to an borderline set of glyco rod bearings.

I don't want to take any risk. Can I fix this problem in some kind or do I need another set?

[HKZ Bob]

I am not getting you. Glyco is the rod supplier for Porsche. What choice do people have to buy.

[gottarideduc]

HKZ,

Don't mean to confuse or worry you, quite the contrary.
Your choice is aftermarket and dealer supplied. I can assure you that the factory supplied rod bearings are different from the aftermarket ones that come in the red Glyco box.
However, as I stated above, for a strictly street engine, I believe you're going to be ok with them. My elaboration on oil clearance served to illustrate our approach to checking and fitting the parts. To reiterate: absolute dimensions are a good guideline, but a crank pin at the limit, a rod bearing shell at the limit of thickness tolerance, and a rod at the limit combined, could result in wrong oil clearance.
Just make sure your rod and crank are reasonably round and when all is assembled there is proper clearance. BTW, check with the bolts that will be installed. Different bolts can torque up differently and even throw the rod dimensions off.

[Eagledriver]

It is possible that the bearings are out of tolerance however it it much more likely that the rods are the item that is out of tolerance. If the rod big end is too big the inside diameter of the bearing will be too big not through any fault of the bearing.

I would do the measurement of the crankshaft and determine if you will have excessive clearance (more than .003 inches). You could also use plastigage (sp) to check the clearance on the crankshaft. If your clearance is excessive you need to machine the rods or grind the crank and use the next size bearings.

-Andy

[HKZ Bob]

Eagle I will measure my rod as well. but what kind of wear do I have on the rod.
I used a torque of 50 Nm. This is a value from Porsche.
Waynes book says 20 Nm and 90 degrees.

what value is correct for a 2.7. What is the metric conversion of .003 inches clearance.
Here the tolerance of the crankshaft rod joints.

51.990 - 51.971 mm.
My values are 51.983 to 51.985 mm.

Regards Bob

[engguy]

"What is the metric conversion of .003 inches clearance."

.0762 mm



"Here the tolerance of the crankshaft rod joints."

51.990 (2.04684 in) - 51.971 mm.(2.04609 in) Thats around .00075


My values are 51.983(2.04657 in) to 51.985 mm.(2.04664 in)

The my values fall with in the Here tolerance. the .983 and .985 mm fall between the .990 and the .971 mm.
Unless I am missunderstanding you.

[HKZ Bob]

Here my values.
I am screwed up with that setup.


crank rod pin--------- Rod dia----------------Clearance
51.985mm------------ 52.065mm------------ 0.080mm
51.980mm------------ 52.057mm------------ 0.077mm
51.980mm------------ 52.061mm------------ 0.081mm
51.980mm------------ 52.054mm------------ 0.074mm
51.985mm------------ 52.058mm------------ 0.073mm
51.985mm------------ 52.061mm------------ 0.076mm

[Eagledriver]

If it were me I'd assemble it as is. If you are worried about it then get the rods machined smaller. I don't have my spec book with me but I bet the wear limit is greater than what you have.

-Andy

[davidppp]

Hello there.

The numbers look fine to me: there is an obvious "digit bias" to the measurements and this suggests they are not terribly accurate..but good 'nuff IMHO...

What matters much more is taper and out of round..pins and big ends..

It is well worth using the Sunnen machine to check the rods for the latter...pins are easy..

Kind regards
David

[HKZ Bob]

The rod bearings no 1
are 1.983mm to 1.982 mm thick.
The Glyco spec. book says they should have 1.990mm. There is the 0.015 mm which I am missing.

Should I return them?

[Wayne 962]

Originally Posted by HKZ Bob

Dear All,
I used the original std rod. They were never been rebuild. Of course I used a set of used rod bolts for measurement purpose and tighten them with 50 Nm.

Eagle I am not intending my engine for race purpose but I want a good engine.

My question is do I have to worry of low oil pressure @hot, due to an borderline set of glyco rod bearings.

I don't want to take any risk. Can I fix this problem in some kind or do I need another set?

All bets are off if the rods haven't been remachined. Over many years, they become egg-shaped and need to be rehoned to the proper size. If not, then they will deform the bearings a bit...

Hope this helps,

Wayne

[HKZ Bob]

Wayne good that you join this issue.

If you look at measurent report, the rod no. 1 is very round.
52.050mm from A-A front & 52.066mm from B-B.

The Rod No 1 without the bearing has 56.012mm front / 56.014mm rear.

The lower half shell has thickness 1.982mm front / rear the upper has 1.983mm front & rear.

With 56.065mm I am out of spec. That what´s your book is telling me. My crank rod diameter is with 51.985 in spec.

"51.990 -51.971 mm"
-------- crank-rod pin----Rod dia (D)- clearance
Rod No.1--51,985mm...52,065mm.......0,080mm
Rod No.2--51,980mm...52,057mm.......0,077mm
Rod No.3--51,980mm...52,061mm.......0,081mm
Rod No.4--51,980mm...52,054mm.......0,074mm
Rod No.5--51,985mm...52,058mm.......0,073mm
Rod No.6--51,985mm...52,061mm.......0,076mm

Rod big eye tolerance "52,020-52.059 mm" . I don`t meet this value.
Rod bold Torque 50 Nm

Wayne could it be that my bearing set is bad. The thickness should be 1.990 mm. I have 1.982mm. Do you saw these issues in one of your rebuilds and can I get a glyco set which is on the lower spec limit?

Regards Bob

[davidppp]

Hello there.

The table of figures on the Opel sheet are confusing to me..but clearly show the shells are installed and the surfaces are far from cylindircal.

There are several possible reasons for this.

The essential stating position is round big end housings..

I'd have no worries re the big oil clearances per se, but plenty worries about random deviation from cylinders of either rod or pin.

Kind regards
David