For years I have had a slant six motor that I have dropped in different project cars or had sitting on a stand waiting to get rebuilt. I used to be certain it was a 225, but a few days ago I noticed for the first time that there is a raised "G" cast on the back of the block below the transmission bolt pad. I have never pulled it apart to measure the rods.

I bought the motor from a guy restoring a 68 dart. He said he didn't want it because it was a 170, but I looked at the number pad by the alternator and read it to indicate a 225.

Anyway, here is the block ID pad numbers:
PT 22 R 217011(46 stamped over a partially obscured 34) then a maltese cross.

The casting number on the driver's side of the block is:
04136
2463430-6

The G on the back of the block got me thinking that maybe the guy I bought it from was right and it is a G block 170, not an RG block 225.

Can anyone answer this for me?

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Casually looking for a Clifford hyperpak intake for cheap.

That's an RG block, a 225 made at Trenton Engine Plant on July 7, 1967.

Maltese cross indicates 0.001" undersize crankshaft and bearings. Usually followed by R (and numbers) and/or M (and numbers) to indicate which ones are undersize, guess no numbers means "all".

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一期一会
Too many people who were born on third base actually believe they've hit a triple.

Now I am really confused. I know this motor came out of a 68 dart and I have successfully mated this motor to three or four post 68 automatic transmissions with no problems (well, one transmission cracked in half, but that is another story).

But, if it is a 225 I am happy. I'll figure out what to do with the crank bushing size thing later.

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Casually looking for a Clifford hyperpak intake for cheap.

A engine made in July of '67 would most likely make it into a '68 model year car. August is the begining of the "new model" year.

Kesteb's explanation is likely correct. Also, I'm relying on that "2170" being an accurate transcription (that's the date code). Also, we're assuming this was an all-original engine, not a rebuilt with a '67 block and a later crank.

In any event, it's a 225.

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一期一会
Too many people who were born on third base actually believe they've hit a triple.