I have a 1970 442 convertible purchased from the original owner, show states that this is the original motor, with a pile of paperwork going back to new on the car. My confusion is, on the engine stamp pad the stamp reads "870Zxxxxxx" every thing i have read states that the vin stamp on the engine block should read "30Zxxxxxx". Has anyone else encountered this? All the other casting and date codes on the engine assembly seem to check out.

Thanks!

 

A 1970 block SHOULD start with a 30, where the 3 is Oldsmobile and the year is 1970. The third character is the assembly plant - your Z would indicate that the engine came from the Fremont, CA plant. Does the VIN match the last eight characters of the VIN derivative on the block?

 

Yes it does indeed.

 

How clean is the area you're looking at? Are you sure the "8" isn't really a "3"? Use a tooth brush to clean the area if it is dirty. Then report back. Don't know what to tell you about the "7".

 

I wonder if the block could be a warranty replacement?

 

How could i tell?

 

Warranty or any replacement blocks have a blank machined pad. Dealers were not known to stamp the pads of these blocks, though.

 

Is it possible, as will Chevy 454's, that if the owner had the engine block rebuilt- including decked, that the original stamp would have been destroyed and the machine shop would have restamped it?

 

Anything is possible, and I have seen blocks and heads that have additional stamping, but it has been (as I said) additional, and is just some unrelated letters and/or numbers.
I wouldn't think the numbers you posted would be a machine shop stamping.
I'm with Ken, have you take a *really* close look?

 

I going to chalk this up to a factory stamping screw up. The original owner bought the car never had the motor out. It is obvious that car has never been apart at all before the motor was pulled to be rebuilt and this stamping anomoly was discovered. The bottom line is that this is a nicely restored, original drivetrain car with a factory stamp error. I am cool with that.