What better candidate for our experiments into 318 power-playing than the weary war-horse in our '68 Barracuda? |
Building high output begins with a solid foundation. We brought the 318 to Precision Speed and Machine, in Delano, California, for the machine work. Dave Massey bored the block, followed by a torque-plate honing to a bore size of 3.950 or .040-inch over. Final displacement worked out to 324 cubes. |
Bob also line-honed the crankshaft bore. Done properly, the bores can be made perfect without changing the centerline appreciably. |
Later 318/360 heavy-duty rods are basically the same forging introduced with the 340 engine, but with unbushed small ends for pressed pins. The rods all matched to center-to-center length, and were fitted with ARP bolts and resized. These rods are very durable in street/strip applications like ours. |
Putting together a 400hp engine is a lofty goal; doing it with a pump-gas street 318 is an accomplishment. Bolting one together without any custom grinding, porting, special machining, or other smoke-and-mirrors trickery may seem impossible, but it makes it that much more palpable for the average guy. we've featured plenty of more advanced engine builds, but the beginner may wonder how to get there with all the custom mods involved. Well, this one is for the Average Joe--a straight bolt-together deal even a first-time engine builder can put together. Ours made exactly 400 hp with a little tuning on the dyno. Yours will make the same, if the battle plans laid out here are followed exactly.
Why build a 318? Some may argue there is never a reason to build the Mopar 318. When the time comes to rebuild a small-block, the 318 should always be cast aside in favor of a 360. We won't argue. A 360--built properly--will always have a torque advantage over a 318. However, 318 cores are free for the asking, and that offers some economic incentive. But the real motive usually isn't a matter of cost. The bottom line is like it or not, 318s are being rebuilt by enthusiasts every day. Some guys have a certain sentimental attachment to these cute little engines. sometimes it's just the desire to retain the car's original powerplant. And some guys dig the idea of blowing doors in with just a 318. Count us in that last group. We were intrigued with working out a combo that shows how to really make one run. Our goals were straightforward:
The engine would be based on a regular 318.The engine must run on 91-octane pump gas or less.The camshaft must be daily-driver streetable, at least in a hot-rod sense.The build will not include any exotic, rare, unusual, or excessively expensive parts.The parts will be bolted on out of the box with no custom tricks, massaging, or porting. The final output would break the 400hp barrier.The Build
The subject of our build was the engine from our '68 Barracuda fastback. The 318 was putting out almost 200 hp at the rear wheels with an antique Edelbrock Street Master intake and four-barrel carb, along with a dual exhaust featuring the stock exhaust manifolds. The output wasn't terrible, but the blue smoke and blow-by certainly were. The engine was just worn out, as we found when the heads were popped to reveal well over .010-inch bore wear. It was the perfect candidate for our buildup. With a goal of 400 hp under the above noted constraints, we had to consider every aspect of the combo very carefully.