With the pan off my 312 engine, noted the following; counterweight marked M 030. I presume that indicates the Mains are .030 under? Also marked T 020. Is that a reference to top & .020 oversize pistons? Also marked BB35? And nearby marked 1966. Possibly a replacement crank? Just curious.. Thanks

Paul

Paul:

The T .020 indicates "throw .020", so the rod bearings are .020.  The other marks are probably a crank grinder or engine rebuilder markings.

John - "The Hoosier Hurricane"

It would be prudent to run a mic or dial caliper over the journals and verify that the journals are indeed sized as indicated.  Some crank grinders do not mark the cranks as to the amount turned while others stamp them in odd places or very lightly making the markings hard to find.  The existing markings could be from a prior machine shop visit while later visits may not be evident without measuring the crankshaft.

Lorena, Texas (South of Waco)

Another thing that does not happen much anymore is to find a throw with a different cut than the others. This was quite common in the early sixties when jobbers used a portable crank grinder to undercut a crankshaft after a failed bearing.



Check on the back of each bearing shell to see that they are all marked .020 and as Ted said also marking could have been from a previous grind.

marv