Re: Engine Swap Economy?
After performing the 289 to 390 swap years ago on my 68, the one thing that I would say is it wont be a cheap endeavor as compared to sticking with the 289. Motor mounts will be changed, the small block radiator will need to be swapped to a big block radiator. Don't know about the 67, but the 68 has different bracketry for the mounting of the radiator. You can use the small block radiator, but it will more than likely want to overheat in traffic (at least mine did). The outlet of the radiator for the small block is probably on the passenger side, 390 will need it on the drivers. You can cheaply aleviate this, backyard style, with some black threaded pipe however. Transmission lines will need to be redone. Cheap way is some rubber hose, pulled through a garden hose for protection. Not pretty, but works. If you got A/C, then need different bracketry, which I'm finding a bear to find myself (or at least cheaply). Driveshaft will need to be modded. The choices for heads are, getting a set of 8 bolt heads and buying a set of FPA headers (bout $800), they're the only ones that make an 8 bolt header for a Fairlane (that I'm aware of at least). You can go cheaply (but would not advise it), shave the corners of the traditional log manifolds and beat the shock towers in ( preferably notch the towers if your going to go this way). Going this route however will cause you to have to partially pull the engine should you blow an exhaust manifold gasket. (Ask me how I know). Then find a competent muffler shop to make the tight bends next to the drivers side outlet. You can get the 14 bolt heads (what I like to refer to as the bastard heads), find a set of GT manifolds. This however will limit you on header choices. I don't think anyone makes a 14 bolt header other than FPA. Or go with the 16 bolt heads (CJ heads) with CJ manifolds, FPA headers, Hooker. You can however search for a set of 8 bolt heads, post-66 era (if my memory serves) and have them drilled for 16 bolt. The tranny crossmember will have to be moved back about 3". If column shift, address that issue. That C4 will have to go and be replaced with a C6.
I won't address the mpg question, different style driving of course effects fuel economy. When I swapped it in, I went with Comp Cams 268H grind, had a noticeable idle and still produced 15-17 in HG or so at around 900 rpm. Just got done going through the engine again, getting it setup with the Tri-Power and 6-speed so I went with a little more cam and went with the Comp Cams XE272H, which has actually given it no worse of an idle sound, but the vacuum has went done to 12.5-13 in HG or so at 900 rpm. If you have any more questions about a small block to FE swap, gimme a holler.
I'm not saying its not worth it to swap from a 289 to 390, if I had to do it over again, I would still have swapped. But when I dove into it, 15 yrs ago, I didn't fully think things through. I addressed issues as they arose and was on a shoe string budget.