318 to stock 340 power level questions.

2 Darts said

The ports on the 318 heads are smaller than those on the 340. A 360 head will have bigger ports but it also has a larger combustion chamber. This will reduce the compression ratio. The 68 318 already uses the tallest piston in the "stock" piston inventory. If you want to recover compression, I'd suggest an aftermarket piston rather than milling the head and manifolds.

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Larger ports aren't necessary for what the OP is looking for. In fact, larger ports aren't really needed until you're up past the 350 hp mark. The 302 heads that everyone seems to like are small port heads. With some porting, these heads are capable of 400 hp.

And the larger 360 chambers would require a severe milling, or new pistons in order to maintain compression (I don't think the OP was looking to do a rebuild.)