How to know what size main bearings to order. Engine builders please help.

Guys,

I'm just wondering...

When building a motor how do you know what size main bearings?



Do you have a batch of different sized bearings to test for fit - install and measure to see if it's within tolerance, if not try another size and measure for fit again and so on until you find the right size.

or...

Do you measure the gap between bearing cradle and the crank then order appropriate sized bearings?


This might sound a daft question but there is reasoning behind it.

The cheap way with tools commonly available is to plastigauge the clearance. First each block and crank is marked with it's original bearing "Suggestions" the service manual does a good job explaining this. This would be a good starting point to try your first bearing if using plastigague. The plastigauge gives you a clearance which may be large, tight or in spec. Too large or tight you would need to change bearings and try again.

If available you can also mic out the crank and main/rod inner diameters and measure the thickness of the bearings to find a proper sized one as well. Someone on here may have a chart that sizes up the thickness of the available honda bearings which would help reduce the number of bearings you would need to purchase.

I have already purchased the bearings but just very curious what the procedure would be for a professional garage to determine the sizes needed.

Just to make it more fair, this is a high horse power engine and it is crucial that the clearances are spot on.

Just wondering if a professional garage would order a selection of bearings to try and see the best fit or if they would measure then order.

I guess that would also depend if Honda lists the size of each bearing per color for the Nsx?

Aren't you using a stroker crank? Why try to use cheap aluminum Honda bearings when you can go aftermarket?

Very worried for you if the garage you've taken it to does not know the basics of engine assembly.

Surprised that the BC crank was not supplied with bearings or they could not tell you the journal sizes and therefore the bearing sizes required?

Mac Attack said:

Aren't you using a stroker crank? Why try to use cheap aluminum Honda bearings when you can go aftermarket?

Click to expand...

Brian Crower supplies ACL big ends and specify you use oem Honda main bearings.

Contacted ACL and they don't make the mains.

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NSXGB said:

Very worried for you if the garage you've taken it to does not know the basics of engine assembly.

Surprised that the BC crank was not supplied with bearings or they could not tell you the journal sizes and therefore the bearing sizes required?

Click to expand...

They only supply the big ends.

They also don't specify what size, they just leave you to measure what size. I'm guessing variances in the machining process maybe.