what is "shielding" and "broach marks"??

[smitty]

Does anyone know what is meant when a corvette is described as "shielding is correct" and "broach marks correct on block"? thanks

 

[ChuckG]

I'm sure that shielding refers to the proper and correct ignition shielding for that particular year of Corvette. There were variations in the ignition shielding between the years. This is the shielding that covers the distributor, wires, spark plugs, etc.

Ah....broach marks When the engine was machined at the engine foundry, Flint or Tonawanda, a special machine "milled" the deck surfaces. We're talking about the block surface where the heads bolt on. This special machine was a broaching machine. It wasn't like a vertical or horizontal mill....it was like a huge wood plane.

The blocks were pushed through this machine and the deck surfaces were "trued". This process left fine lines on the engine stamp pad on the passengers side of the block. These faint lines were parallel to the crank centerline.

Then...the engine assembly date and suffix were stamped, and later on, the VIN derivitive of the car was stamped.

SO....the stampings were placed over this distinctive looking milled surface.....the "broach marks" left by the "broaching machine". If a block is decked, and the numbers removed, the milling machines used today usually leave a "swirl" pattern on the stamp pad. Some try to duplicate the broach marks using sandpaper, files, etc., but it's tough to do.

SO....correct broach marks IMPLIES that it is the original engine for the car....OR maybe not Chuck

 

[smitty]

thanks for the great information Chuck!