Is this an oddity or just Mopar weirdness?

[John Wymore]

I recently pulled a 340 4bbl engine out of a 1970 Dart I purchased. Engine block has a casting date of 6-30-70 but motor build date is 336th day of 1971 and it is an HM designation (1972, Mound Rd.). Engine also has steel crank and 2.02 J heads although I have no way to know if they are original. Was it common for blocks to sit around that long before being built up?

Build Number is: HM340P 37800050

 

[diymirage]

just today i read of someone who had a 71 cast dated block in a 73 model year car

 

[SGBARRACUDA]

just today i read of someone who had a 71 cast dated block in a 73 model year car

Yup that was me. I don't know what the longest amount of time that ever existed between casting date and build date. But I have owned a late 71 cast date 340 that had a 73 build date and was confirmed by the stamped number on the pan rail as a 73. I recorded the block info somewhere but I have no idea where it is now.

 

[John Wymore]

The most ironic thing about this whole deal is that I am building a proper numbers "F" year motor for the car which as it turns out will be essentially identical except for the assembly date. I'm a lunatic!!

 

[ragtopfury]

So your 340 came out of a 70 Dart, but was built in Late 71 for an early 72 car..... sounds to me like a previous owner of the 70 did a motor swap sometime in the last 45 years or so..... was the 70 a real 340 car? Is it a warranty replacement from back in the day? Did a previous owner just have too much fun building what he wanted?

 

[moper]

It is/was not uncommon to stick another engine in a car for repair reasons. A warranty assembly might be older like that. It's hard to really know all the history on a car that's 45+ years old, and of a price point that could have put it into many owners since new.

 

[Darter6]

Yeah, Never say never when it comes to Ma Mopar. But it does sound like it was replaced at some point. A 69 cast date in a 70 car would be common,but a engine date after the cars build date sounds like a replacement.

 

[John Wymore]

No doubt this is a replacement engine and done fairly recently. Cylinder hone marks are almost new looking and it has aftermarket CE 243 pistons. I plan to clean it up and do what is needed to make it a nice long block to sell. Hopefully it will be great for somebody looking for a 340 for a 72 car. In response to the post above, yes it is a true H code 340 4-speed VIN with correct fender tag codes. This is my first Mopar so learning a lot. Trying to get it back to as original as possible.