3-8-Teen Dream

POWER PARTS
Normally, when considering an upgrade sequence for testing, we upgrade parts one component at a time. In this case, we elected to perform all the modifications at once. Headers were already fitted to the engine, leaving only the induction and cam upgrades. Clearly, running the hotter cam combo with the stock induction would be pointless. We felt the induction change would be compromised by the conservative timing of the camshaft. This would understate the benefit of the manifold and carb combo. The most sensible approach in this case would be to upgrade with a complementary induction and cam combo and report on the results accordingly.

The engine was stripped for a cam change. This required the removal of the valve covers, intake manifold, and valvetrain up top. Also, the water pump, damper, and timing case up front were removed. The Comp XE 262H camshaft was installed along with new Comp PN 822-16 lifters. We noted that the Recon long-block was delivered with single-wound valvesprings with a damper coil--a typical first-level, performance-type spring. We determined these springs would be adequate for the camshaft selected. The stock valvetrain was retained and the engine was reassembled.

Intake-manifold selection for the 318 is limited compared to the choices available for the 340 or 360 engines. With the exception of 318 four-barrels, which share the cylinder heads with the 360 engine, 318s were equipped with small-port heads. Of the intakes produced today, the best matches we've found for the 318 port size are Edelbrock's standard Performer and Mopar Performance's M-1 two-plane. We wouldn't consider anything but a two-plane intake for a mild 318 with stock heads, because a single-plane will sacrifice significant levels of torque output for no real gains higher in the rpm range. With a 318, torque is too valuable a commodity to just throw away. We went with Mopar's M-1 and topped it with an Edelbrock 600-cfm, AFB-style carburetor. With the induction selection made, our 318 was buttoned up and we were set for another turn on the dyno.

With the changes in configuration, the 318 retained good idle characteristics. However, vacuum dropped to 15-16 inches Hg at idle. The 318 sounded stronger as the engine was run for the cam break-in procedure. Dropping to idle speed scarcely produced an audible lope. We set the timing to the same setting previously found to be optimal and pulled the engine against the SuperFlow brake. Output surged to 272 hp at 5,100 rpm and 338 lb-ft at 3,000 rpm (the bottom of our pull range). Right out of the chute, power was up by 83 hp, with a 55 lb-ft increase in torque--not a bad gain with only a cam and induction change. We could tell the fuel mixture was a little fat with the Edelbrock carb, which meant we had the potential to make more power with a little mixture tuning. Unfortunately, we were short the required jets to tune the AFB carb. We wanted to further explore the power potential of this combo, so we decided to change the carb to a 650 Demon, for which we had a vast assortment of jets.

Fitting the Demon carb to the M-1 intake required a 1-inch spacer to allow the linkage to clear the manifold mounting surface, so a BG spacer was added at this time. Adding a spacer to a two-plane manifold will typically result in the torque curve shifting slightly upward, enhancing the top end of the power curve at the expense of some lower-end power. We made the swap and set about zeroing in on the optimal jetting, and indeed found power. In this case, the sharper jetting overrode most of the torque penalty expected by the presence of the spacer. We found a minimal loss at the bottom of our test range, while predictably enhancing top-end output. Our 318 now produced 282 hp at 5,000 rpm, and 340 lb-ft of torque at 3,600.

We were pleased with the results of our experiment with the 318. A quick calculation showed that the output of our Recon remanufactured test engine was enhanced to the tune of 93 hp by an intake, carb, and cam change. If we had begun with the stock iron exhaust manifolds, the gains would have registered well over 100 hp. While just the raw numbers are a substantial gain (considering the baseline output of some 189 hp), the changes raised the engine output by a staggering 55 percent. While 282 hp isn't going to get a horsepower freak like Brule wild with excitement, it's enough to feel a real difference compared to your stock 318.