Big end bearing help

[Dolomite_]

My green and brown sets of big end bearings have arrived and I have measured them up, and once again its not going to be as easy as I hoped.

Im not sure if I've read it wrong but my con rods are C2 C2 C2 C2, my plastigauge measurements are 0.050mm 0.050mm 0.050mm 0.038mm. And to throw more confusion when measuring with the micrometer I get a clearance (32 - the diameter measured) of 0.0138mm 0.0163mm 0.0163mm 0.0087mm.

I measured with the brown bearings first and was surprised at the big gap. 0.050mm is too big what is the tolerance? The connecting rod chart is a bit more confusing than the main bearings chart.

[Nurse Julie]

Did you measure the crank Lukas, it may well be very worn.

[Dolomite_]

Did you measure the crank Lukas, it may well be very worn.

If I'm reading the wear tolerance on the graph correctly, the wear is within the tolerance. All below 0.016mm

[Deano400]

When you say 'my con rods are C2 C2 C2 C2', is the C and 2 on either side of the conrod or have you got the Cs from the crank?

[Dolomite_]

When you say 'my con rods are C2 C2 C2 C2', is the C and 2 on either side of the conrod or have you got the Cs from the crank?

Yes, the C and 2 are on either side of the conrod, I don't know if they're relevant to the graph. My web codes are 1 1A 1A 1A 1A and the crankcase codes are BAAAA.

[Deano400]

The Cs on the conrods are the weights, the only thing that matters about that is they are all the same.
Take the As from the webs and your conrod shells are A2, A2, A2, A2 which is Yellow.
Using Green or Brown should give you tight tolerance. Are you just tightening them or torquing them?

[Dolomite_]

The Cs on the conrods are the weights, the only thing that matters about that is they are all the same.
Take the As from the webs and your conrod shells are A2, A2, A2, A2 which is Yellow.
Using Green or Brown should give you tight tolerance. Are you just tightening them or torquing them?

Im torquing to 14.75 lb ft.

It says 14.5 - 15.9. Should I bo going higher? I always go middle to lower end of the range.

[Deano400]

I always go middle but I can't see that 14.75 would be a problem.
If they are new shells then it should come in spec no problem.

[Dolomite_]

I always go middle but I can't see that 14.75 would be a problem.
If they are new shells then it should come in spec no problem.

Yeah new shells just a big clearance.

Im just surprised at the clearance. The Haynes manual says 0.018mm to 0.048. I might need to go to black.

[Bryanj]

I think you are missreading the plastigauge chart or the micrometer ifvit was the gap you say you would probably feel play

[Dolomite_]

I think you are missreading the plastigauge chart or the micrometer ifvit was the gap you say you would probably feel play

I'll give it another go tomorrow. The measurements for the mains went fine, unless it was just one of those days today.

[McCabe-Thiele (Ted)]

When you check the big end bearings iirc the two slots for the bearing shells are on the same side plus the weight code marks will then be in alignment. Have you fitted the big end cap the wrong way round when taking the Plasitgauge readings.

For reasons that seem contrary to common sense the axis for mains & big ends are transposed the number code for mains are on the vertical axis with the letters on the horizontal axis.  For the big ends (con rods)mits letters vertically numbers horizontal.

My big end tollerances were all pretty much the same at 25 microns each a lot tighter than the mains clearances that were 38 microns. I had Green shells in all four of my big ends the codes on my crank were mostly illegible.

[Dolomite_]

measured again and the clearance looks like its more along the lines of 0.038mm 0.050mm 0.050mm 0.025mm. I might order a set of black and see what that shows.

[Deano400]

Not sure going to Black is going to help.
You’ve posted two sets of readings and got different results, so not consistent readings.
Set 1         0.050mm 0.050mm 0.050mm 0.038mm
Set 2         0.038mm 0.050mm 0.050mm 0.025mm
Are you giving everything a clean between readings? No remanence of oil, plastigauge or anything else that may affect your results.
Conrod and cap aligned with the C and 2 always matching?
Conrod installed with shell tabs to the exhaust side?
Torquing progressively on both bolts i.e. not torquing one up then the other?

[Dolomite_]

I took 2 measurements each time. Cleaned them in between and made sure it was the correct direction. I've ordered some blacks anyway as I need to do an order at DSS. Just need to wait for that and some more plastigauge. I'll take pictures next time too.