Glyco Big End Bearings

[Rosco_NZ]

So I said to the machine shop the big end bearings may be a bit variable .. when I caught up with them again, they agreed thicknesses were all over the place ... but they had ground the part lines in each case to suit and get to spec ... I’m just not sure how this can be possible, while retaining round BE shape and exact rod length .. are these guys geniuses or bull artists ...???

[drgouk]

Hi Rossco, Big end bearings are lensed, meaning the bearing has an oil wedge from about 2 o clock to 4oclock, and 7to10 o'clock, the amount of wedge is determined by the bearing eccentricity. Your bearing clearance is measured in the 12'Oclock position. Never heard of grinding bearings at the parting line. This how ever will have no effect on your rod lengths.
Maybe what they did do was, resize your big end tunnels to suit the bearings, and there varying thickness, Re sizing the rod tunnels, does involve grinding the rod caps, and closing down the rod cavities, Then honing them back to tolerance, So for example, You had one thin shell, and it required the rod cavity to be at the smallest end of the tolerance say for a 2.4-2.7 being 56.00-56.019mm, You would hone the rod to 56.00mm, fit the shells and check the bearing clearance. Hopefully the smaller tunnel size will close down the bearing a bit more and make up for the thinner shell thickness and get your bearing clearance in spec.

I would have brought a few set of shells and checked the shell thickness with a dial thickness gauge, and made up a constant set out of the 2 sets, If they vary that much.
Also a decent set of aftermarket rods are a good move, less messing around. Lighter, good rod bolts etc, etc.

Are you in Auckland?

[911S_1975]

Are still Glyco big end bearings not very consistent in size? Or that issue has been addressed?
Planning to buy Glyco bearing for my 1980 3.0sc big end and conrod bearings.
I´ll plastigauge check them anyway.

[Rosco_NZ]

Thanks for reply’s .. I’m in Christchurch but do get to Auckland sometimes, I lived there for 10 years previously.
Seems Glyco bearings from SA, at least as far as Porsche BE’s go get a bad report .. I heard some rebuilding a 964 had similar issues so not limited to a single size.
Thanks for clarifying the method, no grinding of shells themselves but method described sounds like what they did. Aftermarket rods would be nice but I thought ti rods were a maintenance item requiring check & rebuild. I’m building a street engine .. are there other non ti items out there?