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

moparmat2000 said
Stock teener pistons TDC at .080" to .100" below the deck. Thsts a serious loss in compression. This is compounded with heads designed for a bigger bore engine along with the associated valves for a bigger engine. To make a teener run, you need pistons that change direction at the deck, or a couple thousandths below the deck not 80 to 100 thousandths below. The valves , ports, and runners need to be sized for the bore it's got. The whole throw bigger at it does not apply. Putting 340/360 top end on a stockerish 318 bottom end, actually hurts it, not helps it. It slows down port velocity.

ir3333 said
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

Have you actually tried what you say can not work? I have run a 273 with 72 340 J heads. Best it ever ran, and that is with a 3.665 bore and 67 cu in smaller. No valve notches in the block. No port velocity problems. Not sluggish. Not torque limited. What compression loss? 675 heads are about 68 cc per chamber and a .020 milled J head is about 69 cc, at .040 you are about 65 cc. Bore is the smallest adder there is. I used to put 360 heads on 318's all the time. Never a complaint, never a dog. Do you know how to tune an engine and set up a transmission? I would never run a stock 360 cam in anything. Would a low compression 318 beat a 10.5:1 340 with X heads, no, but it will beat the snot out of a 318 2 barrel.