Strange 318 Block

Really enjoying this thread on the 318 Blocks and 318 X Race Blocks.

Here is some more good info on the X Blocks from BigBlockDart.com:

jyrki:
Re: 318 X block
It was the old direct connection race block, offered years before the currently unavailable R-blocks were available. It was delivered with a 3.91" rough bore, and could be bored up to 4.10" without much problem. It was a beefier casting, the weak areas of the factory blocks had been fixed, and the main webs were extra thick and accepted four bolt caps. Some were delivered as two bolts, and some four. It's a good base for a powerful LA engine, that unlike the later R-blocks accept roller lifters etc just like the stock factory blocks.

(abodyjoe 2008)
Re: 318 X block
A good X-block is worth about $1200 maybe more. should have a big X cast on the front of it and the dipstick hole wasn't originally drilled out.

DJV Cuda 2008:
Mine is about 25#'s heavier then standard LA block. (this I wanted to know, George Jets)

Like stated 3.91 rough bore supposedly can be taken out to 4.125
the deck is thicker, the nickel content is higher than standard blocks, and the main caps are stronger, i forget what they are made of but they are stronger.

The blocks were used in Pro Stock until the late 70's early 80's, mine is a 79 casting.

Scamp408:
Re: 318 X block
X in front and back
All weak areas beefed up. blocks were also used in Nascar late 70s and Iroc in 90s.

jyrki:
They sold the block bare with the rough bore only. Bore it, install stock oversize pistons, and other stock 318 internals & externals, and you have a stock 318. The fact that and engine has got that block doesn't necessarily mean it will be huge in power, but that block is a very good foundation for a powerful LA engine.

scamp408:
Re: 318 X block
If there is no X its not an X block. They used a 318 casting # on the X because they need the 318/340 main bore.They didn't have 340s anymore so it could not be a 340 #. The X means it's a race block, big diff in how it was made: Cast Iron mix, wall thickness, main web thickness, deck thickness, all weak points were addressed.