SB race block and heads ID?

I think these are W5 heads and the block is a race block but not sure if it is an R block or a later version? The casting numbers are different than the Mopar numbers so it gets confusing.

Block is a mopar X block. Should have an X cast on the passenger
side front of block below the deck surface. Block precedes
the R block series. It has filled in pan rails, thicker deck
and bore thickness.

Okay, I'll look for the X. I was told by the owner that it was an R block but the part number didn't match up. The owner said it was an R block with W9 heads but I'm thinking now that it is an X block with W5 heads.

I believe r blocks have an r on the pass side front near the deck. Those aren’t w9’s.

X or R blocks will have a designator cast into the RT front.
X
R
R1
R1A
R2
R3
R4
R5

The casting #s are virtually useless given the amounts of variations that were available. A couple of my R blocks have actual "P" part numbers die stamped on them, but I dont recall where at.

There are a few variants of W5s....post some more pics of the heads. Particularly the rocker lay-out and the ends of the heads.


The world of R blocks is a total rabbit hole. Chrysler screwed up more than a few. Ive seen them with undrilled oil galleys. I currently have 5 of them, including one of the ones that got sold with the wrong cam tunnel

Ryan Johnson's web page used to have a lot of good info about the different blocks. I have an R1 59* and it is an oddball because it takes the 340 oil pan where most take the 360.

There is a web archive of his FAQ page that has some info.

https://web.archive.org/web/20050206201421/http://shadydellspeedshop.com/faq.htm

That's the same casting number as a run of the mill 318 block... should be able to see a big X on the front.


I bought a 318 one time because I assumed it was the x block when he told me it had 4.070 bore pistons in it and a rod knock, I told him if it did have 4.070 pistons in it I would buy it and sure enough it was 4.070 but it was not an X block, the bare block weighed only 122 LBS, it had 12.5 forged pistons, forged crank and huge cam but the cylinders were fine.

No guessing about the heads, they say W5 right on them.
Block will have a huge X on the left front side( if looking at it from the front of the car) if it’s an X block. Otherwise it’s just a 318.
The X and 318 do both come with same bore size, 3.91

quick google image search...is this what an X block looks like?

https://www.forabodiesonly.com/mopar/threads/318-340-race-x-block.460755/

Yes

It is an X block. I looked at it again today and the X is obvious now that I know what to look for. Owner said it was an R block but obviously he didn't notice the big X on the front.

X block with W5 heads.

Hope he didn’t pay R block W9 price for that!