Check out my car and talk to me about 318/340 swap

66fs said

You don't get it. Try reading and understand. 318, J heads (71-72 340/360 heads), cam, intake, and 4 barrel carb. It is just 22 cu in difference if you have all the good stuff. Actually if you have the same heads and same compression, it will have the same horsepower, just run a little higher rpm.

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A 340 is already torque challenged.Take away 22 cubes and lower the compression, use mismatched heads and cam and the 318 will fall way short. With the 318's smaller size a 360 2 barrel cam at about .410 and shorter duration would perform better but you still have compression in the 7's and smaller pistons