Conrod bearing thickness determination

[ac427]

What is the correct method for determining the required conrod bearing thickness?

I know about Plasigauge but this isn't the most accurate way.

[bmwfnatic]

What is the correct method for determining the required conrod bearing thickness?

I know about Plasigauge but this isn't the most accurate way.

Measure crank, measure bore of conrod, think about wanted clearance, pick bearing.

[ac427]

Measure crank, measure bore of conrod, think about wanted clearance, pick bearing.

Thank you. Are the crank journal bearings replaced with the same frequency as the conrod bearings?

[bigjae46]

Thank you. Are the crank journal bearings replaced with the same frequency as the conrod bearings?

No. Main bearing issues are almost non-existent on factory built engines. Not sure about rebuilds or engines with a replacement crank.

[sapote]

I know about Plasigauge but this isn't the most accurate way.

I think this is the most accurate method for selecting the bearing size.

[digger]

normally you determine the clearance you want and fit the correct nominal bearings and then depending what the actual clearance is you then make a decision from there as to whether you get a thou bigger shell and use on one or more halves or try different brand etc. Plastigauge is probably the best bet check for a novice with elcheapo tools provided you know the crank pin is round within spec and rod bore is round within spec when it is torqued

[BL92]

normally you determine the clearance you want and fit the correct nominal bearings and then depending what the actual clearance is you then make a decision from there as to whether you get a thou bigger shell and use on one or more halves or try different brand etc. Plastigauge is probably the best bet check for a novice with elcheapo tools provided you know the crank pin is round within spec and rod bore is round within spec when it is torqued

Interesting you mention cheap bolts, cause i got ARP's in the mail for my rod bearing job

I have a M11 engine 2001

Would it be safe to plastigage with the old M11's first, then fit ARP last?

I know the ARP are reusable, though if i don't have to use them twice, would be a bonus

[ac427]

Interesting you mention cheap bolts, cause i got ARP's in the mail for my rod bearing job

I have a M11 engine 2001

Would it be safe to plastigage with the old M11's first, then fit ARP last?

I know the ARP are reusable, though if i don't have to use them twice, would be a bonus

I was told that the official line from BMW was to re-use the OEM M11 bolts

[digger]

Interesting you mention cheap bolts, cause i got ARP's in the mail for my rod bearing job

I have a M11 engine 2001

Would it be safe to plastigage with the old M11's first, then fit ARP last?

I know the ARP are reusable, though if i don't have to use them twice, would be a bonus

cheap tools i mean cheap bore gauge, indicator and mics.

Just use the ARP bolts they wont get hurt. Note you are supposed to size the rod bore with the ARP's torqued, so to me id only be using the ARP if that is a possibility otherwise the M11 are reusable if you are doing this in situ

[BL92]

I was told that the official line from BMW was to re-use the OEM M11 bolts

Maybe 20 years ago, when the engines had low miles on them
Reddish isn't convinced in reusing the M11 =

[ac427]

The only way to get new M11 bolts from BMW is to buy new rods from BMW.
Apparently they say to re-use the M11 bolts.

[sapote]

The only way to get new M11 bolts from BMW is to buy new rods from BMW.
Apparently they say to re-use the M11 bolts.

This is interesting as what if you lost a bolt?

[ac427]

This is interesting as what if you lost a bolt?

You gain a conrod.