Not really talking about 2 barrel engines. I'm never going to build a 2 barrel anything for myself. What a limit on power. We started talking about a 12 second 273. Dan the Man introduced the 318 as he jumped into the end of a thread without reading the rest. As raw material, I personally prefer a 273 over a 318. I kept 273's and 340 small blocks. I have built plenty of performance 273's, 318's, 340's and 360's over the years. 273's and 340's are about zero deck hight. 64 to 67 273 heads have closed chambers. The same year 273's have a forged crank and bushed rods, not a problem for me, although I see no problem with a cast 318 cranks either, although I doubt any performance gain. Having built a 1.88 intake J headed 273, 318s, and low compression 340's with the same heads, cam, and induction, I have not seen much difference from a larger bore, all things being equal. But I'm not a low rpm torque kind of guy. Nor do I care about drag racing myself. The 273 works perfectly in my 66 Formula S for the limitations I place on my own cars.