Engine serial number mystery

[Palmer Moe-par 68]

I am looking at the numbers on one of my engine blocks and finally found the serial number of the motor as follows:
PT383R22161618

From what I could find, the decoding goes like this:

PT: Trenton plant
383: 383 cu. in.
R: ?
2216: 10,000 day calander date code
1618: serial number for the day

My confusion is on what the R means. Some other serial numbers I have seen have an S instead, but I have yet to find a source that acknowledges this extra character on some engines. In my parts catalog I have for 1968, the book never mentions a character being there. It states that it should say PT38322161618.

Does anyone know what it means?
Is it a "Replacement" block, since I couldn't find a vin on the back of the motor on the top flange where the transmission mounts against.

-Mr. Moe-par
1968 Road Runner, 1968 Coronet, 1968 Coronet, 1969 Dart

 

[Russ69Runner]

Have you looked on the right side of the motor where the oil pan is to the front of the motor down under the distributor side. That is where the number's are on my 383.

 

[Palmer Moe-par 68]

Well, I already have the number, it was on bottom rear where the oil pan connects to next to the transmission. I just want to know what the R in the serial number means.

On the pad at the front of the motor on the top next to the cylinder head, it has an R as well, but that just means "regular fuel". Maybe that R in the serial number means regular fuel as well?

 

[69hemibeep]

It was assembled by a pirate R

 

[Russ69Runner]

That is a good one. I don't remember an R on my motor. Sure someone knows.

 

[Palmer Moe-par 68]

R you sure?

 

[Russ69Runner]

I surfed the net. and found specks on Mopar motors. It was worth reading on the history of the 383. It told me a lot but did not remember any thing on an R stamped in the place you show it. In the motor vin stamp would be RR. Mine has that but no it is not the motor that came with the car. But is a good motor. Also reading the 383 magnum but don't know what year it came out. Have heard the term regular motor or Special. In other cars. So maybe this holds true to mopar also.

 

[Palmer Moe-par 68]

Yeah I am assuming it means something along the lines of Regular or Replacement. I think the fact that I couldn't find a section of a cars vin on the motor would lead me to believe it is a warranty motor. I did some reading and I found multiple examples of 69 and 70 motors that were reported to be "Warranty Blocks", and they had an S stamped on the date code pad in front of the motor number (383). These "Warranty Motors" also carried no vin on the bell housing area, like my motor, but they only had a build date if it was a dealer warranty claim or if a customer bought a whole motor over the counter. Otherwise if a customer bought the motor over the counter, as just the block, it would not have a build date. On other motors, there was a WT either on the pad or in the serial number, and it meant Water Tested. I believe the R is the predecessor to the engine code "S", which I have not seen on a 68 block yet.

 

[Big John]

R is an inspectors stamp.

 

[Russ69Runner]

I knew the Mopar God would have the answer. Thank you Big John.

 

[69hemibeep]

Inspector is a Pirate

 

[Russ69Runner]

No the parrot put's the stamp on and the pirate drinks his rum. RRRRRRRRRRRR!!!!!!!!

 

[quikbird]

Pirate drinks all the RRum and falls down and snoRRes

 

[moparchris]

R means regular fuel.

 

[cosgig]

^^^^ R is “regular” fuel, designating a 2 bbl motor.

 

[cosgig]

^^^^ R is “regular” fuel, designating a 2 bbl motor.

Hmm, I thought it indicates that it was a marine motor. You know….Arrrrrr!