New Vintage Speedster owner with engine question

1914cc      110 cam    8.25 to 1 compression    Built  6/21/21    Long reach plugs

Not sure what RMM stands for but 1914 cc is the displacement of an engine with stock 69mm crank and bored out for 94mm piston and cylinders.

Stock (old) heads took plugs with threaded 1/2" reach - new style heads take 3/4" reach plugs. Plus can be 14mm or 12mm too

Nice having displacement and cam model!

That’s bizarre. Those digits aren’t stamped, they’re cast into the case. (Unless it’s an optical illusion)

Thanks for the help. The digits are stamped it does look raised in the picks. I am assuming late heads then because of "deep plugs"  Maybe RMM is the builder.  6.21.21 looks like the build date. That would be nice to have newly built engine.

I stamp my engines with DPP, I'm sure RMM is the builder's initials.

Deep 3/4" reach plugs are definitely an improvement over the strip-prone 1/2" reach OE setup.

dlear/476......They are stamped. If cast in they would have shadowed casting marks around the data from the "casting slugs" used to make them and allow them to be changed at will by the foundry. Casting slugs look very much like the lead ones used by printers when they "set type" but they are made of harder metal than lead that won't wear out.  

Something I have always wished is that all replacement parts have the actual part number of that particular part stamped, engraved, or whatever method worked best permanently written on each part. That would certainly make things easier later..........Bruce

So strange. No matter how hard I try I can’t “unsee” raised numerals. If you look at it, judging from the shadows on the fins above, it looks like the light source is coming from the right, which makes the shadows in the numerals appears to be raised.

Thanks for the help. Maybe "RMM" will see this post and give me more info on the engine.l have not seen the car in person, so I only have pics to go by. I will be traveling from DE to Missouri to get the car in 2 weeks. I will post pics and info here for more speedster expert advice.

In the Mazda circles, RMM stands for rear motor mount.

Hmm... but why stamp it on an engine??? I am still thinking builder initials, but have not tracked it down yet.