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BlownMGB-V8
Jim Blackwood
9406 Gunpowder Rd., Florence, KY 41042
(5812 posts)

Registered:
10/23/2007 12:59PM

Main British Car:
1971 MGB Blown,Injected,Intercooled Buick 340/AA80E/JagIRS

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Crankshaft rod big end sizes
Posted by: BlownMGB-V8
Date: August 02, 2019 02:47PM

We all know that the crank pin size of a BOPR/SBB is 2", I suppose more properly I should say that standard size is 2.000" But what is the size of the bore of the rod big end? Should be common information, right? But other than machinists who bothers checking? Turns out the spec is not that easy to find.

Now if you are considering aftermarket rods, or offset grinding to change the stroke a bit, these details become more important. For instance, we know that certain Japanese bearing sizes are used in NASCAR engines quite commonly. Exactly what those are isn't quite as well known.

So now to the specific question, given bore sizes below, what is the corresponding crank pin size and what engine do the bearings come from? (assume about a .900" rod width)
2.075"
2.000"
1.980" (1.850" pin size)
1.960"

Jim


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