Ever Wondered What These Numbers Mean?

[moonpup]

While recently cleaning up some parts, I recognized some numbers that I hadn't thought about since I got out of the 240Z car club. Thought I'd post a little something about these in case anyone here was curious about them.

I "borrowed" this from the old car site I was a member on and changed the numbers to reflect the ones that are in the pic in an effort to give y'all a quick easy explanation...

"These numbers are dates in the Showa format. Without getting into too much history, 'Showa' refers to the Emperor of Japan and at the time of your motorcycle's/part's assembly, the Showa period was in existence. The Showa period begins in 1925 (the Emperor's date of birth) and the '42' in the pic added to it (kinda smudged), is the year (1925 + 42 = 1967) and the '8' would be 8th month or August and the '10' would be the 10th day."

So the right side crankcase cover that this number is on, was made (or inspected) on Aug. 10th. 1967.

Voila 

[Mopar392]

WOW DM, learned something new again, your just an overflowing wealth of useful information...DL  

[dcr]

Next time you need to break the ice with a stranger, ask them if they know anything about the Showa date format.

[moonpup]

Next time you need to break the ice with a stranger, ask them if they know anything about the Showa date format.

haha... does it work with women? 

[coxy]

that's very interesting you learn something new every day

listed under  is everything I know about women .
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hope that helps

[dcr]

Probably works better than "you come here often".

[paul]

I learned to read ,  by trying to read Floyd Clymers Cycle Magazine. So this just continues my education. thanks

[ziggy stardust]

Thanks for that Moonpup, I enjoy information as such. I'll try to remember to include it in my next article for Tansha magazine, should impress a few.

Z

[BRT-GTR]

       Hi Mike,
                     Great bit of information. Another piece fitted in the the BS history jigsaw.
    I have often noticed these numbers and thought they could be a production batch code or a date but couldn't reconcile the year. This would explain it.
 Just had a look at two right side covers in the workshop, 42 6 8 and  43 3 9 which do give matching production year dates for GTRs with VIN code dates of July 67 and June 68.
    Not too sure about the last two digits, I agree, they do look like month/day numbers but I don't remember ever seeing a number higher than your '10'. Any of you guys got a part with a number above 10  ??  Did imperial Japan use a different dating system.
   Great post DM,  Brian.

[moonpup]

Not too sure about the last two digits, I agree, they do look like month/day numbers but I don't remember ever seeing a number higher than your '10'. Any of you guys got a part with a number above 10  ?

Hi Brian,

This "dating system" has been discussed quite a bit over on the Z site and by some very knowledgeable "experts" that are well versed in the Japanese way of doing things. I'm confident that the 8 & 10 in my example refer to the month and day respectively.

The Z cars have a ton of parts with these stamped markings in one form or another, with many examples pictured having numbers above 10. Unfortunately, there doesn't seem to be as many opportunities to find these stamps on our bikes. I've only seen 2 or 3 examples myself.

I'll keep my eyes out for more though and in the meantime, maybe some other members will chime in with their finds.

[moonpup]

Here's another right side crankcase cover I had access to. This one is 42.8.12 or August 12th. 1967.

As far as how high the "day" will go, who knows, maybe production for this particular part was limited to the first 2 weeks of the month and then they moved on to another piece? I'm not very well versed on how manufacturing companies do things.

On a side note, 8/12/67 was a Saturday.... 

[BRT-GTR]

Hi Mike,
             Well, that gets us up to 12 but either number could still be a month or a day. I'm not questioning your knowledge on this one, just curious.
 Do any other parts have similar numbers on them. I've just done a quick check on the alloy parts that I can get to easily and can't find one. The set of crankcases I'm working on have been vapour blasted so won't show a number.
Keep up the good work,  Brian.

[coxy]

one of mine says 42 9 26  the other has nothing

[moonpup]

God Bless you Coxy!   

[slawsonb]

The stamping on mine is too faint to read from a July '67 build GTR.
...bert

[paul]

Do the  Hondas,yamahas, etc have these  date stamps on there parts?

[moonpup]

Do the  Hondas,yamahas, etc have these  date stamps on there parts?

Hey Paul, My guess would be yes considering they're all over the Z cars and can also be found on some of the Bridgestone parts. Probably a government requirement of some sort.

Here are a couple stamps I got off the car site to show some different styles. The ones I posted from my Bridgestone show a faint circle off to the bottom of the numbers but they don't sit on top like these nor do they have a Japanese characters as well...

[BRT-GTR]

Hi Mike,
            'Me of little faith'   .    Coxy's number settles it - Year, Month, Day as you said Mike.
    My money would be on it being an inspection mark at some stage in the engine manufacturing process. A final check the engine was timed correctly, gears and kick start worked and everything was in place before the right side cover went on ??    The left crankcase side covers don't have any stamps, suggesting these are not production dating marks.
   Brian.

[slawsonb]

Good guess Brian. Mine was a date of manufacture mark. It would be interesting to see if these are all unique to the specific Bridgestone part or if we find duplicates. Duplicates could indicate a lot code or that multiple engines were completed per day or 
...bert

[moonpup]

I have 3 right case covers available (didn't picture one) and they are....

42.8.10 / 42.8.11 / 42.8.12

3 engines, 3 consecutive days.

I'm sure I saw them on something else, just can't remember what and can't find it or any others at the moment.