X-heads vs J-heads: what's the difference??

69 Cuda 440 said

As Advertised by Chrysler

1968 thru 1970 ~ 340..... 10.5 - 1 Compression-Ratio
1971 ~ 340..................... 10.3 - 1 Compression-Ratio



Piston Height the same for all 4-Years.... +.045" AB {Above Block Deck}
Head Gaskets the same for all 4-Years.... .028" Thickness

Note; According to Chrysler, the late-1970 and 1971 {#2531894} Cylinder Head Castings had approximately
+2.0 CC's larger Combustion Chambers.

Click to expand...

The late Dick Landy was quoted in an article by MOPAR saying his "favorite" readily available cast small block head was the 915 J head with 2.02 & 1.60 valves with the bowls opened up and the head milled to yield 64-68 cc. These heads with a aftermarket intake and carb and headers would be at the 425-450 HP range. He was replying to a question as to how make the low comp. 360 in the dart and dusters run in the high 12's.