Many Mopar fans believe that life still revolves around the original Mopar small-block. Sure, the Gen III Hemi makes great power, but so do the early LA and Magnum engines and parts for those are generally more affordable.

It's also a well-known fact that the cast-iron heads, after proper selection, can be tweaked to make very respectable power on these platforms. So let's go do a little small-block archeology.

Dave Hughes has been building and tuning Mopars for more years than he probably cares to admit. Hughes Engines is all about Mopar power covering all the bases, but he really pays attention to the small-block stuff. Much of this material emanates out of his experience. We'll start with the early, or LA, engines. Yes, there's the polyspheric small-block, but we'll leave those to the vintage crowd. The LA era was expansive, spanning 1964 to 1992 and offered what are Mopar's finest small-blocks.

Current OE parentage no longer services or sells much of this stuff and digging up early castings borders on Indiana Jonestype adventures. Among the older LA pieces, the 308 castings are good. But if you find a set, they're likely either cracked or will require significant machine work to resurrect them. There are better ways.

The next in lineage is the Magnum era heads. These spanned from 1992 to 2004 and were used on 5.2L and 5.9L engines. There's a whole movement that retro-fits Magnum heads to the earlier LA engines with favorite casting numbers like the 466, 671, and 714 heads. But these suffer from thin deck surfaces and can be crack-prone. Like their earlier cousins, a used set will likely need plenty of machine work. But if you find a set in good shape, they're worth the effort.

Our focus here will be on affordable options for the LA or Magnum enthusiast. Sure, there are factory Magnum aluminum heads, but these are essentially a performance dead end. Edelbrock offers a couple of really nice aluminum heads like the Performer RPM Magnum and even a Victor 16-degree head, that we may examine at a later date is there's enough interest, but the price is commensurate with power. For this story, we'll focus on the affordable iron options.

Right out of the gate, Hughes says the most attractive are available from either EQ or Indy in terms of their LA-X option heads. Of maximum importance is that either of these heads will outflow the originals. We'll take the EQ first. But right off, Hughes offers an iron-clad warning. His research recommends that any of these castings immediately be converted to bronze guide liners. These liners offer a better and more consistent surface, especially so for the exhaust that improves durability along with a far more consistent guide-to-stem clearance.

The EQ Magnum Iron Ram heads are offered in two configurations that span both the early LA intake manifold bolt pattern as well as the later Magnum pattern. The intake ports measure 172 cc with 1.92/1.62-inch valves and 62cc chambers that are roughly 6 to 8 cc's smaller than original LA castings. As we know, that'll raise the static compression ratio. The EQ CH318B is the same head with the LA intake-manifold bolt pattern, offering a greater variety of selection. These were originally intended to be used on Magnum engines that push lube through the pushrods yet will accept the use of the earlier and more plentiful LA style intake manifolds. Just for the record, there's also a CH318A head that's identical except that it employs the more recent Magnum-style intake bolt pattern. The port flow numbers are the same between these two versions.

Much of the same points and features of the EQ head applies to the Indy X-LA version with one main variation. The Indy head offers drilled passages that allow these heads to easily retro-fit back to LA engines as long as the proper early head gaskets are employed. These can also be used on early Magnum engines that used passages machined down into the Numbers 2 and 4 cam bore housings before the Magnum converted to oiling through the pushrods. The X-LA also comes with LA pedestals to mount the stock rocker shaft system, but these can also be milled off and the pedestal bosses drilled and tapped for Magnum version individual rocker arms.

Besides the flow improvements from both the intake and exhaust ports on the EQ and Indy heads, there's also the added benefit of a slight bump in static compression. The Indy X-LA chambers fluctuate between 62 and 64 cc's while the EQ's are similar in size at around 62 cc. This is in comparison to the LA version heads that come in between 68 and 70 cc. That may not seem like much, but on a 360ci LA engine even a 4cc chamber reduction is worth a half-point in compression—moving from 8.8:1 to 9.3:1.

Of course, there are no rules when it comes to street performance so there's no boulevard sanctioning body insisting that these heads must remain stock. Hughes offers several upgrades for these iron heads including the iron Ram. Hughes has put these mods to the test and offered up the results. We've taken these charts and created a couple of graphs that make the comparisons a little less complex.

While many enthusiasts tend to concentrate on just the peak flow numbers, that really isn't in the best interest of making a great decision. If you think about it, both intake and exhaust valves make the move up to peak valve lift twice once on the way up and again on the way down. So residence time, if we can call it that, will be significantly longer compared to peak lift. That makes the flow numbers between 0.200- and 0.450-inch lift range of more interest to the discerning street engine builder/enthusiast.

We've plotted Hughes' test of five different stock intake ports, and, as you can see, up through even 0.450 valve lift they all flow very similarly with the larger 2.02-inch intake valve on the tested heads, indicating that it offers a slight advantage. But shift your attention to the next graph that illustrates what happens to all the castings with some minor CNC porting and valve size upgrades. This graph illustrates that a mildly modified head with a stock 1.92-inch valve size delivers some impressive flow numbers over a stock port fitted with a larger 2.02-inch valve.

You'll notice that the larger 2.02 valve looks pretty good from low lift up through 0.400 inch of valve lift, and then it flattens out and is essentially no better than the smaller valve. The reason for this is that at low lift, the larger valve has the advantage of more curtain area—or a larger window for potential flow at low lift. This curtain area increases with higher valve lift numbers. However, at 0.400 inch of valve lift, the total flow capacity of this curtain area exceeds the port's maximum flow potential, making the addition of the larger valve of less value. But once the port is enhanced with porting, the flow radically improves. Now you know not only how these ports flow, but also what creates the numbers you see. You're now a smarter engine builder.

The point here is that a smaller valve with some intelligent port work can deliver very stout numbers that'll clearly benefit even a mildly cammed street engine. Conventional wisdom holds that a good set of heads, even when combined with a very mild cam, will still deliver strong performance, while poor flowing heads with the best cam in existence will still underperform. Airflow is the key and combined with a good cam, the symmetry produces great power.

On the iron head flow chart (Chart 1), you'll notice the final column on the far right lists something called E/I percent. This refers to the exhaust-to-intake (E/I) flow percentage. This expresses in percentage how efficient the exhaust flow numbers are relative to the intake port. This particular chart from Hughes' own flow bench compares the CNC-ported 1.62-inch exhaust valve flow numbers to the CNC-ported 1.94-inch intake port flow numbers. Good numbers will be in the mid-to-high 70 to low 80 percent relationship, which is exactly where these numbers come in. It's beyond the scope of this story to get into camshaft recommendations but generally these higher percentages mean the exhaust side of the head is working exceptionally well and won't restrict the flow out of the engine, especially at higher engine speeds. That often equates to potentially higher peak horsepower.

There's much more to all this than we can deliver in a short story, but armed with this information you can now see there are several approaches to building a budget-based LA or Magnum small-block that'll make great power, have excellent throttle response, and generally be a sweetheart of a street engine even using supposedly "ancient" iron heads. It's not so much what the heads are made of as how they flow. For a healthy street small-block, the only disadvantage to these heads is their additional weight. On the flip side of that iron coin, there's nothing wrong with making decent power and saving a little money along the way.

See all 17 photos

See all 17 photos This is the Indy LA-X head designed as a direct replacement for the LA head used from 1967 to 1992. It uses pedestal mounts for shaft rockers along with LS-style intake bolt angles and valve cover.

See all 17 photos This is the EQ cast-iron head CH318B that was originally designed as a replacement head for the Magnum but the "B" suffix means it employs the earlier LA engine intake manifold bolt pattern so it can use the earlier LA engine intake manifolds. It also offers thicker deck surface and is far less prone to cracking than the OE heads.

See all 17 photos All the flow numbers used in this story were generated on Hughes Engines' Seanz flow bench. Here, Craig Tackett checks port velocity with a small probe. All flow tests are performed at 28 inches of water test depression.

See all 17 photos This chart compares five iron castings on the intake side. This chart looks at an OE LA 1.94 valve casting, the Mopar Performance R/T head with 2.02-inch intakes, a Magnum 1.94 valve port, and the EQ Iron Ram with both 1.94 and 2.02-inch valves. As you can see, the EQ head with the bigger valves performs with good mid-lift flow up to 0.500-inch valve lift.

See all 17 photos The holes in this Indy-X head in between the combustion chambers (arrows) are the production oil passages for lubrication up to the valvetrain. Magnum era engines oil through the pushrods, which means a changeover to different lifters are necessary when converting an older LA engine to Magnum heads.

See all 17 photos This photo illustrates the difference in intake bolt angles between the original LA head (left) with its perpendicular bolt angle and the newer Magnum version (right) with near 45-degree bolt angle.

See all 17 photos This Hughes valvespring update package (PN 1199) replaces OE beehive springs that are limited in load and valve lift capability with simple drop-in installation that increases the spring rate while also able to accommodate cams with valve lift up to 0.550 inch. These are single springs with dampers, steel retainers, and new locks.

See all 17 photos Ben Hoitink is assembling a pair of Hughes-modified Magnum heads with new stainless 1.94/1.62-inch intake and exhaust valves using the HUG-1199 valvespring package.

See all 17 photos This is a Hughes-prepped CNC chamber that's part of the cylinder head modification program that creates as much airflow with a set of 2.02/1.62-inch stainless valves as that from a much larger 2.055-inch valve in an otherwise stock head. Also note the bronze guides that are essential on all Hughes heads.

See all 17 photos Bigger valves don't always deliver a flow advantage. In this Hughes flown bench test, note how a smaller 1.94-inch valve with the CNC porting delivers greater flow than the larger 2.02 valve in the stock port. Of course, combining the larger 2.02 with CNC porting is the ideal combination for maximum flow with these ports.

See all 17 photos Another important consideration when upgrading valvesprings on a stock iron head is the 0.920-inch valveguide outside diameter. Most performance beehive springs will demand a smaller diameter, which requires custom machine work. But the Hughes performance spring upgrade kit (PN 1199) negates that necessity and will accommodate up to 0.550-inch of valve lift.

See all 17 photos All Hughes-assembled heads are verified for consistent installed height so that all the springs offer the same seat and open load.

See all 17 photos When adding a cam with more lift, a crucial area of concern is retainer-to-seal clearance. The production height from the spring base to the top of the guide is usually 0.650-inch (+/- 0.010-inch). Both EQ and Indy heads have reduced this height as shown here to under 0.500 inch for provide additional retainer-to-seal clearance for a high-lift cams.

See all 17 photos LA engines were originally designed with a 59-degree lifter angle that when used with a flat-tappet lifter creates the unique pushrod angle seen here. This also creates pushrod clearance problems where the pushrod travels through the head. Aftermarket Magnum heads require a simple machining operation that Hughes can perform when using Magnum-style heads with an early LA block with a flat-tappet cam.

See all 17 photos This graph illustrates the rather dramatic exhaust port improvements possible with mild porting on the Indy LA-X head while maintaining the original exhaust valve diameter.

See all 17 photos

Flow Numbers Representing all the Hughes Iron Heads

Lift Stock 1.94" CNC Prep 1.94" 2.02" Only 2.02" CNC Super Prep Gain Over Stock Stock 1.62" Ported Exh. 1.62" E/I % vs. CNC 1.94 0.1 58 69 73 71 13 59 62 90% 0.2 109 147 136 145 36 103 125 85% 0.3 168 212 192 213 45 145 176 83% 0.35 192 234 201 238 46 157 192 82% 0.4 212 250 213 257 45 165 201 80% 0.45 228 259 231 268 40 172 205 79% 0.5 236 264 244 275 39 177 208 79% 0.55 238 261 251 273 35 180 206 79% Show All

Stealth Flow Test

Valve Lift OEM Stealth CFM OEM Stealth CFM Int. Int. Change Exh. Exh. Change 0.10" 66 71 5 51 80 29 0.20" 89 144 55 103 124 21 0.30" 136 192 56 131 149 18 0.35" 176 211 35 136 156 20 0.40" 184 226 42 140 160 20 0.45" 186 231 45 142 168 26 0.50" 184 223 39 141 168 27 0.55" 183 218 35 142 168 26 Show All

Note: These flow figures are representative of improvements

that can be made with stealth porting on both heads. Actual flow may vary with different heads due to variations in the non-ported areas.

Parts List

Description PN Source EQ Iron Ram head, 1.92/1.62, pr. HUG-4675B Hughes Engines EQ Iron Ram Magnum heads HUG-4670B Hughes Engines Indy MA-X iron 2.02/1.62 blended HUG-20300C Hughes Engines EQ LA Iron 2.055/1.62 Super Prep HUG-4680SP Hughes Engines EQ Ch318A head, bare, ea. HUG-4666 Hughes Engines Indy-X LA style 1.92 stainless pkg. HUG-20301B Hughes Engines Indy-X Super Prep CNC head pkg. HUG-20301SP Hughes Engines Magnum valvespring update kit HUG-1199 Hughes Engines ARP head bolts, Iron Ram Magnum ARP 144-3604 Hughes Engines Show All