I agree with HP2. Here's my take on things... It sounds like you said "it needs to be rebuilt", and he had it rebuilt. But, there is a huge difference between "rebuilding" and "performance building". They are related, but not the same. And, most shops that "...can rebuild it. No problem.." may have problems making the power levels you want within visual restrictions. So, what's the fix? Well, technology always improves. It improves the materials the parts are made from, it improves the science that went into designing these engines, and it improves the machines that do the work. To get more from a stock design, you have to use the most modern stuff from all 3. And if you're spending that much $$ on a resto, you dont really (IMO anyway) want to hurt the collectability and value of a car by not using factory looks. You can get 400hp from a stock appearing 340. Manifolds, small carb, etc. But, things have to be altered slightly, and that costs money. The first thing is, you can change the internals. The simplest way to get 400hp and huge torque, is to go stroker. But you dont have to, and in the interest of keeping the engine matching and the value high, lets go with a 3.31(stock) stroke 340. You need more compression. They said they were either 10.5:1, or 8.5:1 depending ont he years. In both cases, they lied. (they designers spec'd it, but there was poor production line standards for the machining and assembly) A high compression 340 had at best about 9.8:1, and the later 72-73s had about 7.8:1. You want a true 10:1 static ratio, which involves using modern pistons and blueprinting the block machining so they end up where they are supposed to in relation to the block's deck surface. You will need the mains align honed, the block's decks square decked, and the cylinders bored and properly honed for the modern rings. This should be done on all modern equipment. Not stuff that looks like it's from the 60s and "works fine for this older stuff..." You will want the rods reconditions with modern ARP bolts in them. And you'll want the crank, pistons, and rods internally balanced. You want the heads to be redone, but with performance in mind. That means new valves. They dont have to be stainless (I like using stainless swirl polished, but that's just me), but they will need to be back cut, and they will need seats cut with straight pilots and seat cutters, not stones. They will need unleaded seats installed for the unleaded fuel. They will need new guides. They will need the spring seats cut for double springs, and the guides cut down for positive seals. The blueprinting operations may mean you will need new pushrods. All this stuff combines to make a package that looks stock, but moves more air much better, and will last for a very long time that way. The cam needs to be spec'd for use with the stock intake and carb, and the manifolds and closed exh system. This is one area where HUGE gains are made with little loss in driveability. I would think the XE274h would be a nice cam, or perhaps something similar from Engle or a custom unit from Scott Brown. In any case, the factory distributor and carb will need carefull attention to set them up to perform with the new parts too. You should have no trouble getting 400hp from a stock look build. If you dont mind visual changes, 400 hp can be done with a stock plain rebuild and some bolt ons like headers, a carb, and ignition. The trick to a stock look build is to never give up any power to losses from lack of accuracy or overlook any area to make small improvements. There is no trick to making power if you dont mind things looking non-stock.
