When using the hypereutectic...
When using the hypereutectic pistons, make sure to pay attention to the special gapping instructions from KB, or catastrophic engine failure may result. The KB specs should supersede the gap specs from the ring manufacturer.
For our engine build, we opted for the CH318B castings with the earlier intake manifold bolt pattern, which is compatible with the Edelbrock Performer RPM Air-Gap intake manifold we already had. The cylinder heads were purchased as bare castings, which require assembly and valves. To fill out the castings, we went to Dr. J's Performance to have the castings assembled and dialed in. Dr. J's ordered a set of valves from SI, a manufacturer of good quality stainless steel valves at a very reasonable price. SI catalogs valves in the stock valve diameters of 1.92/1.625 inches, and the stock length. These valves take the OEM Magnum bead lock-type keepers. To complete our cylinder heads, OEM Mopar Magnum retainers and locks were used along with COMP's 901-16 valvesprings. The stock-length SI valves were set up at 1.600-inch installed height, which offers adequate coil-bind clearance with the .560-inch lift delivered by the Magnum rockers' 1.6:1 ratio. Dr. J's did find, however, that the retainer-to-guide clearance would not be sufficient, so they machined the guides to provide clearance at the guide boss.
Upon inspection of the cylinder head castings on Dr. J's flow bench, we were impressed with the out-of-the-box flow for the Engine Quest heads. Overall, the numbers were stronger than the OEM castings. If some is good, more is better, so Bryce Mulvey of Dr. J's suggested porting the Engine Quest heads. Since we wanted to test the heads in as-cast condition, we ordered a second set of heads to experiment with modifications. Bryce reported that the heads responded well to porting modifications (see sidebar: "On the Bench"). We had Dr. J's assemble a second set of the Engine Quest castings using the same hardware, but this time with basic full porting, and a set of larger 2.03/1.625-inch valves from SI.
Clevite P-series bearings...
Clevite P-series bearings were used for the main and rod journals, and the crank was installed with the factory fasteners. We checked the bearing clearance at .002 inch, and the endplay measured .006.
Assembly And Testing
With the major components ironed out, we had a core 318 block machined with a full block prep at Precision Speed and Machine in Bakersfield, California. The combination of the Engine Quest heads at 62cc combustion chamber volume, the KB pistons at zero deck, and Fel-Pro head gaskets put the engine's compression ratio at 9.85:1, a nice ratio for our street camshaft on pump gas. We had Precision resize a set of stock, later-model 318 connecting rods using ARP bolts, and fit the pistons to the rods. The stock 318 crankshaft was ground .010/.010 on the rod and main journals, and then balanced to the new parts combination. The short-block assembly was straightforward, with a stock replacement Melling oil pump and Clevite bearings. We used a set of Speed-Pro moly rings file fit to .022-inch top and .018 second. The COMP cam was lubed with moly grease, and installed at 106-degrees intake centerline using a new COMP timing set. Buttoned up with an OEM oil pan and windage tray, and a stock front cover and water pump, the bottom end of our project was completed.
Up top, we installed the Magnum-style Engine Quest heads using an LA-engine head gasket from Fel-Pro, and a set of OEM Magnum cylinder head bolts. Since all Magnum engines were originally equipped with hydraulic roller cams and our short-block is flat-tappet equipped, the combination requires longer pushrods than the stock Magnum units. We measured the required length with the stock Magnum nonadjustable rockers we were using, and ordered a set of COMP Magnum pushrods (PN 7960). The Engine Quest heads accepted all of the OEM Magnum valvetrain components without issue. We bolted on an LA-engine series Edelbrock Performer RPM Air-Gap intake manifold, and it fit the hybrid Engine Quest CH318B heads perfectly. The finishing touches included a Holley 750 HP carb and an MSD distributor and wires.
A factory windage tray went...
A factory windage tray went into the bottom end to help control oil. We used a stock oil pan, but improved it by welding in a fabricated baffle.
With the 318 together and ready to run, we headed over to Westech Performance Group to quantify the power at hand. Our baseline combination is a true bolt-together engine combination, using all essentially out-of-the-box parts and very little in the way of custom tricks. We spent the first few minutes of run time letting our COMP flat-tappet cam break in properly, and the engine certainly sounded healthy. With the timing set at 34 degrees, we spent considerable time dialing in the jetting, and we were pleased to see the power closing in at the 400hp mark. With the mixture set to perfection, we had a high number of 399 hp at 6,300 rpm, with the engine pulling sweetly to 6,500 rpm. The lightweight Magnum-style 5/16-inch-stem valves clearly showed better high-rpm valvetrain operation than the chunky 3/8-inch-stem units traditionally used in older LA-style engines.
We were really close to breaking the 400hp barrier, with little left to explore besides the timing. Our baseline setting is usually about optimal for a Mopar small-block; however, we pulled two degrees of timing out, for a total of 33 degrees. We dropped a few horsepower across the board. Next, we twisted the MSD distributor in the other direction, now with 36 degrees total. The engine liked the change, netting us 402 hp at 6,300 rpm. That is very good output for a street 318, with a nice use of the engine's rpm potential. While that would be enough to go home proud, we still had the Dr. J's ported heads up our sleeve. We pulled out the wrenches and tore the 318 down to a bare short-block right on the dyno.
The cam was carefully degreed...
The cam was carefully degreed to the recommended 106-degree installed centerline spec. With our COMP chain, everything ended up right on the specifications without any adjustment required.
It wasn't long before our 318 was once again ready to thunder, this time with more airflow than ever. The modified heads were not substantially enlarged over the as-cast units, but the flow showed significant improvements across the board. Of interest was the larger valves, going from a 1.92-inch size to a larger 2.03 spec. Conventional wisdom would decree that the larger valves would hurt low-end torque, but we had our doubts about this commonly held belief. Our dyno graphs would tell a story here.
Once buttoned up and running, there was little to do but pull the handle for the power numbers. Interestingly, we found the torque right at the bottom to equal the initial baseline, and then the ported heads began to pull away with the torque advantage just seeming to add on as the rpms flew with as much as a 21 lb-ft advantage gained by 5,800 rpm. On the horsepower side, the ported heads just kept pulling harder up top, making full steam at 6,200 rpm at 425 hp. Ironically, that's the rated horsepower of a stock 426 Hemi; we were more than satisfied with these stout numbers from our little, overlooked 318.
Magnum Head Conversion
The Engine Quest cylinder heads are designed as a performance-improved replacement casting for the factory Magnum heads. So what makes a Magnum head a Magnum? Let's look at the changes from the earlier engine family, referred to as the LA-series engine. Magnum heads have a revised valvetrain, relying on rockers grouped on paired pedestals rather than the shaft-mounted system of earlier engines. Oiling is supplied through the pushrods via the lifters, so the lifters must have oiling provisions. Most aftermarket lifters are so equipped. Older small-blocks oil via a passage in the block feeding the rocker shaft. To go along with the rockers, the pushrod length is revised to match; we recommend measuring the actual length required for the individual engine.
Along with these changes, the Magnum castings have a revised head bolt package that does not interchange with earlier engines. At the valve cover, the machined valve cover rail takes 10 bolts rather than the LA engine's five, though the earlier valve covers will still bolt on. Another peculiarity of the Magnum is a change to vertical intake manifold fasteners, which precludes intake manifold interchange. The Engine Quest cylinder heads are available in a configuration that takes the standard early-style manifold.
 Cylinder heads will make or...  Cylinder heads will make or break any build, and here we opted for the Engine Quest CH318B. These heads have compact 62cc chambers, ample quench area, and improved port flow in comparison to the stock castings. |  These Engine Quest castings,...  These Engine Quest castings, like all Magnum heads, feature exhaust ports with much improved contours compared to earlier LA-series production castings. Note the hardened inserts installed at the valve seats. |  Intake port flow is quite...  Intake port flow is quite good considering the substantial pushrod intrusion near the port opening, which is characteristic of all production Magnum heads. Any porting here will unlock even more flow. |
 Since our heads came as bare...  Since our heads came as bare castings, we ordered a set of SI stainless steel valves, as well as COMP's No. 901-16 springs. The retainers and keepers are used factory Magnum pieces, specific to the 8mm valves. |  Engine Quest's replacement...  Engine Quest's replacement heads are based upon the Magnum design, so the fasteners must be the corresponding type, which are different than the earlier LA engine bolts. |  For the valvetrain, we simply...  For the valvetrain, we simply bolted on a set of used stock rocker arms. A combination of a flat-tappet hydraulic cam and Magnum heads was never factory produced, so making it work takes a special pushrod length; 7.650 inches worked perfectly for us. |
 With the Edelbrock Air-Gap...  With the Edelbrock Air-Gap intake and Holley 750 carb installed, we were up and mounted on the dyno. The two-plane Air-Gap is an awesome street intake on a warmed-over 318. |  Our basic engine package may...  Our basic engine package may not seem like much, but the dyno told another story, with our 318 just cresting the 400hp barrier after tuning. |  After the stout numbers were...  After the stout numbers were turned in by the stock Engine Quest heads, we had the engine torn down on the dyno in short order to get a second set of Engine Quest heads ready with basic full porting by Dr. J's Performance. |
 Bryce Mulvey brought the ported...  Bryce Mulvey brought the ported heads with valves installed, but we would reuse the springs and retainers from the set hot off the dyno to eliminate any variables to the results from different valvesprings. |  We heaved the metal on the...  We heaved the metal on the deck, sewed her back together with the same parts, and then sat back and let it eat. From the numbers turned in by the as-cast heads, these castings are well matched for a street 318, making us wonder if our hydraulic-cammed street 318 could actually use the extra flow of the ported heads. |  We were impressed to see a...  We were impressed to see a significant gain in top-end output, and even a little surprised to see that the bottom end of the power curve gave up nothing. With a solid 425 hp now being generated from our easy-to-build 318, it has the grunt to surprise even the naysayers! |