Stroker Crank Bearings

[downforce22]

I have gotten my stroker crank and am working on the oil seal to make the 3.0L stroker.

I was wondering which bearings I need and the differences between yellow and blue bearings. My e30 manual shows the clearances and standard sizes of the m20 crank and my (limited) measurements show approximately the same values.

Main bearings ~59.99 mm

Rod Bearings ~25.0 mm

I have read about the early and late bearings having/not having the oil groove in them, respectively. Apparently the m54 crank I am using had the same oil groove used on its application.

So should I use early or late style bearings?

Thanks!

[SkiFree]

I never go by color, just leads to screwups.

What main bearings were in the block? (this is what you'll need to order.)

[MR 325]

The oil groove you're referring to pertains to differences in early and late M20 blocks. You need to order whichever bearings your block takes. Check your tolerances and see if you can run standard size bearings, this is obviously most ideal. Don't worry about that color nonsense.

[bmwstudent]

So which blocks have the groove in the lower bearing? I took my crank out and my block side bearing shell has the oil groove in it, is it an early or late block?

[jlevie]

The color of the bearings is important. You figure out which to use by measuring the diameter of the crank journals and picking the color(s) from the table based on those measurements. That results in the correct bearing clearance. Journal diameter measurement requires a micrometer that can read to a ten thousandth of an inch. While most of the time one color of bearings will work the bearings on a given crank, you can encounter a crank that requires more than one color.

The locking notches in the block and bearing caps determine which bearings you need. Early production has a single 2.9mm notch and late production will have one or two 2.0mm notches and can have crescent shaped oil groves in the bearing cap. You can use the late bearings in an early block, but not vice versa.

[SkiFree]

The color of the bearings is important. You figure out which to use by measuring the diameter of the crank journals and picking the color(s) from the table based on those measurements. That results in the correct bearing clearance. Journal diameter measurement requires a micrometer that can read to a ten thousandth of an inch. While most of the time one color of bearings will work the bearings on a given crank, you can encounter a crank that requires more than one color.

The locking notches in the block and bearing caps determine which bearings you need. Early production has a single 2.9mm notch and late production will have one or two 2.0mm notches and can have crescent shaped oil groves in the bearing cap. You can use the late bearings in an early block, but not vice versa.

No, the color system is not important. It can, and has led to confusion, (just ask anyone who has rebuilt an M10), what's important are the numbers/tolerances involved.

And contrary to what WorldPac states, you cannot use late main bearings in the early block ( though you can use half of them ... http://www.r3vlimited.com/BOARD/showthread.php?t=256117 )

[downforce22]

Thank you for the replies, and pictures/thread SkiFree.