It seems like there is an alphabet soup of engine and head combinations out there: LSx, RO7, P7, D3, and the W7, W8, and W9. When straying from a traditional engine build of a small-block (insert brand here), unless you are an über-gearhead, it’s next to impossible to know all the different iterations and permutations. That’s why when it comes time to build something really special and off the wall, it’s best to head to a specialist. For small-block Mopar engines, that means talking to Brett Miller of Dillsboro, Pennsylvania.
Miller wrenches on flavorless mom-mobiles during the day, but when the bell rings 5 o’clock, he sprints to his home shop where the real fun happens. It is a place where metric wrenches are meant to feel unwelcome and if you can’t tell the difference between a pushrod and a connecting rod, you might be unwelcome, too. Honestly, Miller and his wife, Tina, are as nice as the day is long, and PHR has gotten to know them well as multiple-time competitors in the AMSOIL Engine Masters Challenge (EMC). As alluded to, Miller is a hard-core Mopar guy and has been involved in building serious small-block power since the days of the old NHRA Pro Stock Trucks and later Craftsman Truck Series NASCAR racers.
Not long ago, Miller was trying to figure out what combination would make monster power for the 2011 EMC, and looking through his pile of old “junk,” figured he had enough parts to build a 412ci love child based on one of those Craftsman Truck engines. Miller built the W8-headed Mopar as a dare-to-be-different statement. “I tried to do something pretty neat that wasn’t going to show up otherwise.”
When Mopar first got into racing trucks in the mid ’90s, there wasn’t much in their performance line of cylinder heads that would make the kind of power to really shine. They had just developed the W7 head (“W” for Wedge), but the early versions were sluggish 18-degree valve-angle castings that weren’t a whole lot better than the W5 castings designed for hi-po street cars. They quickly retooled and made a 15-degree version of the W7 that gave them a little breathing room, so to speak, before a totally redesigned head came out. That new head was the W8; it became the standard of Mopar small-block race engines for years to come. Even though a later head called the W9 was cast, it was specifically a lightweight offering and made no more power than the W8.
It was a pair of W8 heads, which Miller had, that gave him the real starting point for this build. Typical to circle track engines of the day, the W8 heads had relatively small runners, which should make decent torque, but Miller says they didn’t flow worth a darn. He said they just laid over above .650-inch lift. Unacceptable. He went to work doing his magic with a grinder and flow bench to see what the potential was. “The intake runner is 3 square inches at the flange. It’s 1.405 inches by 2.25 inches, minus corner radii, and 4 square inches over the short turn.” By removing a bunch of material in just the right places, the results were intake ports that flowed 404 cfm. That is well into big-block race head territory. And a big-block usually needs 3.4 or more square inches at the opening to make the same numbers. The exhaust was in great shape as it was, so Miller didn’t need to lean on it nearly as much.
It isn’t just the peak flow number and minimum cross-sectional area of the port that makes a cylinder head work. The way the air moves throughout the entire port makes as much difference as anything else. This is shown in a velocity profile, which is basically a map of how fast the air moves at different places in the port. Figuring out average port velocity in feet per second requires just a fairly simple formula:
FPS = 2.4 × cfm/(port area in square inches)
This is a good start, but comparing this number against different places within the port gives a better view if there are dead spots that might require filling in with weld or epoxy, or extremely fast spots that require more grinding to slow them down. A common place to probe the velocity with a pitot tube is across the floor of the short side radius. If this number is over 400 feet per second, then you can bet there is going to be some unhappiness in the airflow. Keeping the number to 325-375 is a good target and is right where Miller’s W8 heads landed.
One of the weak points of regular small-block Mopar heads is that there’s very little room to widen the intake ports. The W8 heads address that by requiring a heavily offset rocker arm set and offset lifters to shove the pushrod out of the way and allow for all that aforementioned grinding. Speaking of lifters, the block Miller used was set up for double throwdown Jesel keyed solid-roller lifters. That’s because this was no ho-hum stock-block. It was an old NASCAR piece he got for a song since all this “old” technology was out of date. R3 blocks like Miller’s were offered in a number of configurations with different bore sizes, deck heights, and other variations. A quick peek at the lack of an oil filter pad is a quick way to recognize this as a block specifically designed for dry-sump oiling and not a street piece. That particular variant also was only available with a 9.025-inch deck height, destined for skinny, lightweight pistons and a short-throw crank.
The other thing about this particular block is that it is machined for lifters that are at a 48-degree angle as opposed to a 59-degree angle found in stock and some R-series blocks. The shallower lifter angle sets the lifter up in a better relationship between the cam and the pushrod/rocker arm, and ultimately reduces frictional losses along the way. The other benefit is that with a traditional 59-degree angle, getting a solid-roller lifter to fit is pretty much impossible without grinding on the block, as the lifter retaining bar will rub against it. Core shift and unsteady grinder use have led to more than one stock-block being destroyed by grinding into a water passage when trying to fit solid-roller lifters. Beware.
The main motivator for this powerplant is the set of Mopar Performance W8 cylinder heads. Designed specifically for NASCAR use, the heads’ offset rockers hint at the possibility of extra-big intake ports. Though there were several iterations throughout the years with different intake port locations, the exhaust height and bolt locations remained basically unchanged due to rules regulating exhaust port height.
To keep oil from piling up in the cylinder heads, extra drain holes were drilled and tapped to run straight to the oil pan.
On the southern end of the cylinder head oil drain line, a fitting was welded to the Charlie’s oil pan. It’s pretty easy to spot the patch hole in the middle of the side indicating this pan design was originally for a stock-style steering system with the drag link running through the pan.
With the super deep sump design, the oil pump had a long reach to suck up the AMSOIL 10W-30 synthetic, but by keeping it as far from the block as possible, Miller was able to control oil temp. Throughout a number of warm-up, test, and final dyno pulls, the oil never got over 150 degrees.
The bottom end looks similar to any other LA block at first blush. Oh, except for the ARP main studs holding billet steel main caps. And, glancing to the right side, a fitting where the oil filter should be locates where the oil is fed into the block. A minor misalignment when tapping the hole for the fitting led to a little leak, which was easily fixed with some epoxy.
One of the good things about a quality crankshaft like Miller’s LA Enterprises piece is that even when offset ground, the oil holes are still in good enough position not to starve the bearings or create a stress area that could lead to a crack.
Miller picked up this trick billet oil filter adapter and a case of filters for pennies on the dollar. He says that during testing, he normally ran around 60 psi of pressure but if they wanted to pick up power in a hurry, they could just unscrew the built-in pressure regulator and pick up 15 hp.
W8 heads use a dry intake manifold, meaning that there are no provisions to get water out of the heads. Building a water manifold like this is commonplace, and it allows for the intake itself to be pulled off for testing and modification without draining the block.
A tried-and-true MSD Digital 6 Programmable ignition box was triggered by a flying magnet crank trigger. Keeping the ignition box far from the high-output coil is recommended to reduce any possibility of cross talk and ignition misfire.
On the other end of the spark box, instead of a typical distributor, an MSD beltdriven dizzy was used. A small cog replaces the regular bolt on the front of the camshaft beltdrive and motivates a thin belt to spin the distributor. This combination is common in the highest ranks of racing for accuracy and ease of maintaining the engine.
Dale Cubic of CFM carburetors built the Holley 4500-style fuel mixer for the project. Cubic is one of the hidden secrets in the racing world, known to the insiders as a true carb guru who’s built carbs for and tuned some of the biggest racing name engines around. His down-to-earth personality and the fact that he’s readily accessible to look at a dyno sheet help keep him a busy and highly respected asset.
Though it looks massive, this is the smaller of the Mopar Performance intakes available for the W8. In testing, Miller found the big “420” intake picked up 30 horses up top, but just killed the low and midrange power.
It is easy to spot the highly placed intake runners on the head, which feed manhole-sized intake valves. It is commonly considered that the intake valve should not exceed about 52 percent of the bore size. Miller hit it right on the head using a 2.180-inch valve and 4.180-inch bore, giving 52.1 percent. With an intake valve that big, there isn’t room for a huge exhaust valve, so a 1.60-inch valve was used, smaller than the stock Magnum’s 1.625-inch exhaust valve, but able to flow well over 200 cfm.
Miller is a cylinder head guy by nature and a Mopar guy by heart. Combining those two, he spent countless hours perfecting an intake port design, then had it digitized so he could reproduce it over and over. He says that his port design works both on the W8 heads and on the lightweight W9 heads, as well as for customers who want a 400-cfm small-block head. He’s going to need to send samples to PHR
for long-term testing …
A small dome was needed to get the compression up high, but there was some give and take along the way. He had to fly-cut the pistons a bit to clear the valves, then after machining a bit of the valves to thin down the margins, he found his compression ratio dropped into the low 13s. Great for the rest of us, but not good enough for Miller. He went back and milled the decks of the heads some more and shot the compression ratio up to 14.5:1 to take full advantage of the VP Q16 race fuel.
Miller’s repurposed NASCAR powerplant wasn’t just built for show; it was meant to go! Miller pulled the old small-block out of his 2,880-pound small-tire ’66 Dart, and blowing the tires away, clicked off a killer 5.77 at 122.5 mph in the eighth-mile. Not half bad for no traction and a torque converter that didn’t know what hit it!
Yet another piece of this super-mamma-jamma block is the 50mm cam core. Those of the Pentastar persuasion will no doubt know that oiling to the top end is done with the help of the factory camshaft. Oil is fed across a groove or holes in the No. 2 and 4 cam journal then through passages in the block up to the factory shaft rockers up top. This race block with 50mm roller cam bearings is designed to oil the top end through the lifters and up the pushrods so it does not have the trademark cam journal grooves or holes. The thing about special cam cores like this is that they can be really expensive. Miller had a few sitting in his pile of goodies, which he was able to send to Predator Cams to grind for this 412. The other thing about cam cores is that when regrinding them, you can only grind off so much to move the duration and lobe centers around. “I tried to get the duration as short as I could with the lobes I had available. I had a bunch of 50mm cams from that Truck stuff, but I could only shrink them so much and move the lobe separation a degree or two. With that, the cores kind of dictated what I could do with the cams.” That said, the specialists at Predator were able to whittle up a pair of lobes with 255 degrees at .050-inch lift on the intake and 259 degrees on the exhaust. Coupled with T&D 1.8 rocker arms, the valves lofted open to a peak .781-inch lift. Regarding the rocker arms for W8 heads, and any of the W series racing heads, they were very specific about what rocker arms they used. The W7s were more notorious for multiple rocker bolt patterns and locations, but since these were designed for NASCAR use and those old boys in North Carolina were known for moving things around here and there, you might not always get something that works when buying a set of heads and rockers from two different people. Lesson is, if you plan on buying a set of used NASCAR heads, get the matching rockers. This wasn’t Miller’s first rodeo, so he cut that headache off at the pass when he bought the donor motor complete.
To make all the valvetrain components do their dance, the cam had to be coupled to the crank in some manner. More specifically, a Jesel beltdrive joined the bumpstick to a reground crankshaft. Not a cheesy factory regrind, of course. This forged LA Enterprises piece was sent to the delicate hands of Adney Brown at Performance Crankshaft. The specialist took the forging in and offset ground it to pick up a quarter inch of stroke in hopes of increasing the torque in the 3,500-7,500 rpm operating range of the EMC.
Looking to save a little money, Miller found a set of bejeweled 6-inch Carillo rods on eBay for a quarter of their original cost. It helps to shop around. On the top end of the rods were a set of pistons that Miller didn’t want to skimp on. He called his buddy at Wiseco to hook him up with a low-drag skirt design that would work with the 15-degree heads and produce a killer 14.5:1 compression ratio. It wasn’t just the pistons that were maximum effort. The rings were super-skinny low-friction parts common to the top NASCAR ranks. Talking with another pal at JE, he asked what the desired hone job would be. “I’ve read up and people say you can get cylinder walls too smooth. Well, the cylinder walls in that motor were like glass. It wouldn’t even grab lint off a paper towel.” It didn’t hurt that the gentleman honing his block was a guy honing top NASCAR and Pro Stock blocks all day long.
Once Miller had it all figured out how to convert the reciprocating energy of combustion into rotating energy transmitted through his crankshaft, there was the matter of controlling an unwanted byproduct of that rotational motion: windage. Charlie’s Oil Pans has been a major player in building race pans and oiling systems, especially for those inclined toward Chrysler products. Miller called Charlie up and described the combination he was putting together for the EMC. As mentioned before, the block was designed for a dry-sump oiling system but the rules for competition dictated using a wet sump. Charlie whipped up an aluminum pan and pickup that would fit, but it was up to Miller to modify the rear main cap to hold an oil pump. Dry-sump blocks have a solid rear main cap, so he machined it to mount a Melling pump on it and make it all work.
After all the innards were carefully wrenched together, Miller went to work trying to get the most out of the powerplant. That meant heading to his buddy’s dyno at Rider Race Engines and screwing it to the pump. Usually, there are some rounds of ignition timing and carb jetting going back and forth and this was no different, except the efforts weren’t giving the results he knew were supposed to be there. It was time to delve a little deeper into the bag of tricks and move the cam around. He found that with the cam’s 105-degree lobe separation, it liked to be advanced all the way to 97 degrees to get the best average torque and horsepower score across a range of 3,500 to 7,500 rpm. Still, it was lacking down low. “It’s the weirdest stuff that builds score. We put a reducer on the collector from 3.5 inches down to 3 inches, and it picked up 50 lb-ft of torque at the hit.” That was the magic combination that made the fat lady sing. The old girl belted out a whopping 749.4 hp. While he could have spent another day fussing with it to pick up that extra .6 hp, where we hang out that is just one bad 750-horse small-block.
On The Dyno
|412ci Small-Block Mopar
By The Numbers
412ci Small Block Mopar
||412 actual cubic inches
||Predator solid roller
||255/285 degrees at .050-inch tappet rise
||OEM 1.8 ratio
||Mopar Performance R3
||Mopar Performance W8
|Intake valve diameter:
|Exhaust valve diameter:
||Holley Dominator modified by CFM
||MSD Digital 6
||AMSOIL Synthetic 10W-30
||VP Fuels Q16