When it comes to putting together an engine, we need to consider design in addition to assembly. Anyone can pick parts out of a catalog and assemble a motor, but proper engine design requires thought and research. So whether it is a street 318 or a blown nitro Hemi, each choice requires different parts, even if the mechanics are basically the same. Our dirty, but loveable scoundrel, The Royal Scamp, needed a wild wench under the hood, and Evil Betty is her name. Stout but hot, our Betty is a 383 short-deck big block whose goal is 600+ horsepower on pump gas, with the ability to inhale a 200-250 horsepower shot of automotive liquid courage, i.e. nitrous oxide. At that point, she’s a bad girl on a hot date in anybody’s book.
We sourced Betty’s beginning off Ebay, and paid less than scrap price for it. The short block assembly had been recently bored .030”, was clean, and in good shape with a stock crank, stock rods and a set of “vintage” TRW forged 12.5:1 pop-up slugs for 1\8-mile bracket racing. Those heavy pistons, however, had more than a few detonation scars (detonation at 12.5:1, surely you jest), and would not make the grade in our 21st century program. This heavy piston design is not even available anymore for a reason; slugs like this eat up more power during the rotation than a lighter piston and take longer to spin up (decreasing weight at the long end of the reciprocating assembly is usually a good thing). Nonetheless, this motor had pulled a ’69 Roadrunner to mid-6 second 1\8-mile blasts; we are hoping to get our Scamp into the 10s without too much effort, but would need some new parts.
Starting with the healthy block and crank, we shucked the stock rods and old-school pistons for a set of off-the shelf Eagle H-beams and forged pistons from Diamond, which should withstand the forces of our basic 600-hp package and the NOS Crosshair nitrous system. To make reliable power that can also take the abuse of nitrous, we needed forged pistons, but most of the current hypereutectic castings won’t hold up in this environment, at least not on a consistent basis. We would need to keep the compression under 12:1 for pump gas as well, so we discussed our combination with several leading engine builders, including Dave Hughes of Hughes Engines and Ron Beaubien of Diamond Pistons. Keeping with Beaubien’s advice, we ordered a set of pistons that would keep the dynamic compression at 11:1. Some builders may argue that an aluminum head will dissipate heat faster than an iron head, so you can run higher compression without detonation; the short answer to that question is ‘no, it doesn’t work like that.’ Heat is only one factor in detonation, the other is pressure; the more pressure you have, the less heat is needed to pre-ignite the fuel. About the best we can get in our area is 93 octane, but even that is hard to find, the most common range is 86-91; 11.1 is on the edge but should work, with a set of Total Seal gapless rings keeping the oil separated from the combustion chamber.
For cylinder heads, we looked at several options and finally decided on the Edelbrock Victor series 440. To give them the best possible flow in our combination, we shipped them over to Hughes Engines, where Dave Hughes and his crew put them on their CNC machine for some serious port work. Hughes Engines also installed the valve springs (Lunati) and we picked up a set of their specially-designed adjustable offset rocker arms for the Edelbrock Victor series heads. After the CNC port work, the Hughes-worked heads picked up 11% flow throughout the entire lift range, including over 35 cfm in the all-important mid-range lift (.300-.400”) since the valves are open at .300-400 much longer than they are at .600”. Mid-range gains actually mean more than high flow at max lift. A Lunati Voodoo solid roller cam (#60334) went into the block featuring .600” lift (in and ex), 255 degrees of intake duration @.050 (263 ex @.050) with a 110 centerline. The rest of the valvetrain consists of Lunati solid roller lifters, pushrods, and timing chain. The adjustable roller rockers from Hughes Engines allowed us to set the rocker directly over the valve by shimming each one side-to-side; with the solid roller, adjustability is a must.
The Mopar factory oiling system is capable of handling a mildly-built motor, even a fairly stout one, but Evil Betty needs lots of lube, and we needed a good oil pan to fit the A-body Scamp. A Milodon external oiling system and accompanying center-sump pan will provide plenty of flow to maintain pressure while under heavy acceleration.
Up top, Betty got dressed up with an Edelbrock Torker intake and a Proform 950-CFM carb serving as bartender. A Professional Products SFI-certified damper (pn 90013 ) on the crank should keep the harmonics away and everything was bolted down with ARP fasteners, including head and main studs. Supplying the spark is an MSD billet distributor, coil and a 6AL box. That’s about it.
While we would love to put the motor on a dyno, the closest engine dyno is a couple hours away and magazine deadlines are rarely forgiving. Once Evil Betty is buttoned up under the hood, we will have some chassis dyno numbers for you, after all, it’s the power at the wheels that counts. We did, however use DynoSim’s Desktop Dyno software during the design phase of the motor, and in our experience this program is usually within 5% of the actual numbers. Evil Betty should peak out with 613 hp at 6500 RPM, while pulling a freight-train-esque 558 ft lbs from 4-4500. Add on the 200-shot of happy gas, the Royal Scamp, and his hot babe, should leave all opposition in tatters.
Selecting custom pistons
It may not be for everyone, but with modern CNC technology, custom pistons are no longer strictly for the big-budget racer. Mass-produced pistons are not always what you need, especially if you are building an odd-ball engine; conversely, custom pistons are built to your specs. That doesn’t mean you have to have an engineering degree, either. We ordered custom pistons for Evil Betty and all it took was a phone call to the techs at Diamond Pistons in Michigan who crunched the numbers and figured our just what we needed. Custom slugs are not astronomical in cost, either; prices start at about $700 for flat-tops (dishes and domes will cost a little more). With a custom piston, everything is ala cart; pins and rings are not included like they are on off-theshelf pistons, but Diamond does provide locks with all of their pistons. There are extras that can add up quickly to pump up the price, like gas porting and coatings. A full-blown, all-the-extras custom piston set can run $1500, but you probably don’t have to spend that much.
Before you call, you need to know what you want, what you have and what you are planning on doing with the motor. “It all has to do with your combination.” Ron Beaubien at Diamond Racing told us, “Building an oddball combo often dictates a custom piston. A little extra dish, a little extra dome, 9 times out of 10 off the shelf pistons are too cookie cutter. For guys that know what they want and have specific goals, custom pistons are the way to go.” The basic specs are easy- engine make, model and year, displacement, max RPM, bore, stroke, rod length and approximate horsepower. Getting a little deeper into the design you need some info on the rest of the engine as well like the camshaft profile. The engineers at Diamond can take it from here, but the more information you can provide them with, the better. Compression height takes more work to figure – the formula for compression height is (rod length + 1/2 of stroke + piston-to-deck clearance) – Block height. Where things get interesting is that you get to choose different specs like gas porting, oil rail supports, custom coatings, even ring height and width.
The key to ordering custom pistons is to know what you want to achieve with the motor. Consulting the experts at Diamond Racing was probably the best decision we made during this build. We had already picked the heads and the cam, so those variables were set, but we likely would have made a mistake in piston selection had it not been for Ron Beaubien at Diamond (we know, a 12.5:1 motor would not be very streetable). What sets Diamond Pistons apart from the other custom pistons shops is their Mopar knowledge.
“The other custom piston companies are all very good, but Diamond has a little more focus on the Mopar stuff. Our catalog has a about 3 times as much in the Mopar section than the other guys and our shelf-stock represents that too” said Beaubien, “our techs are well versed in the various brands, we don’t leave the Mopar guys guessing, I’m a Chrysler guy myself”. You don’t have to be an expert to order custom pistons; you just have to know what you want. – JB
After picking it up on eBay as an assembled short block, the first thing we did after disassembly was to check the clearances. Since we are using the stock crank, everything should be OK. Frankly, you need a dial bore gauge and a set of micrometers to do this right; calipers won’t do the trick. Plastigauge is acceptable (we still use it to back up our numbers), and Plastigauge can also show problems that a dial-bore gauge won’t, like a weaving line bore. Our motor had .003” of clearance, which is about right for a drag-race motor.
The cam bearings were a little worn, and since we had it all apart, we used this universal cam bearing installation tool from Powerhouse Tools (pn POW101025) to do it ourselves. The tool pays for itself after just a few sets of bearings, and is a good tool to split the cost with your buddies. We used Sealed Power cam bearings, pn Z1453m
The custom pistons from Diamond Racing are lightweight at 675 grams and yield a 11.03:1 compression ratio; this should give us great power with 93 octane. The valve reliefs are directional, so we marked each piston corresponding to the cylinder as well as an arrow to the front of the motor. Assembling the pistons to rods will be simpler this way.
There are two sides of each connecting rod (Eagle pn crs6358c3d), a big chamfer and a shallow one. The big chamfer goes to the outside while the narrow should be to the inside. In other words, the larger chamfer of the 1-3-5-7 rods should be face to the front and the larger chamfer of the 2-4-6-8 rods should face the rear of the motor. This is for clearance of the radius on the outside edges of the crank journals.
The Diamond pistons use Spiro-lox to hold the full-floating wrist pins in place. These are much more secure than round-wire locks, but are a pain to install. We didn’t draw any blood this time, but many builders, even professionals do. You want to lightly stretch the lock before installing, but don’t over-stretch them. This is about perfect. Then one side goes in and you “spiral” them in place. We got them started with a fingernail and finished them off with a screwdriver. It takes a minute to figure it out, but then it goes quickly. Two locks per side for our pistons. When ordering your pistons, ask for the removal notch, if you have to pull a spirolock, you will be glad you did.
Evil Betty uses Total Seal rings (pn M9190), which are file-to-fit. We placed each ring in its own cylinder and filed each one to match, placing it 1” down from the deck. Measure the gap with a feeler gauge; for our motor, we set the top gap to .030”, 2nd ring to .025 and the oil rings were within spec as shipped. We used a Napier-style 2nd ring for better oil control. Napier rings have a relief cut on the bottom edge of the ring to scrape oil away from the cylinder wall during the downstroke.
Even though the top rings are “gapless” you still have to file them to fit. The top ring is actually two rings; a machined groove ring and a sealing ring. The machined ring has a relief cut on the outer bottom side to accept the sealing ring. Both must be gapped correctly and then installed with the gaps 180-degrees opposite each other the result is a complete seal around the top of the piston. Use a hand-file to remove any burrs from the edge after file-fitting with a ring-grinder.
With the pistons and rods assembled, we installed the new Sealed Power bearings (Z2320CP rod bearings, Z4924M main bearings) and coated them with some Royal Purple assembly lube. This is better than the paste prelube, but costs more too. We use it on everything. A set of ARP main studs were installed, then the crankshaft.
You should use a dead-blow hammer to lightly tap the main caps in place rather than drawing them in with the bolts. It is really easy to get them cocked out of shape that way. We torque the new bolts to 90-foot lbs in a series of three torque settings- 45, 70, 90.
We picked up an adjustable tapered ring compressor from Powerhouse tools (POW106030) for this job. Using a piston as a guide, the clamp is tightened until the rings were compressed just under the bore of the cylinder. This worked really well, and no broken rings. These must be ordered to fit within a range of bore sizes.
A trick we learned from an NHRA engine builder is soaking the pistons in trans fluid rather than oil. The trans fluid lubes the walls better for initial startup and flows though the rings, which is important. We also wiped each cylinder with an ATF soaked shop towel.
We tapped the pistons in place with a mallet and torque the Eagle rods to 63 ft lbs (as per the ARP bolt instructions). Don’t forget the rear main seal plate; this should to be installed before you forget about it.
Next we lubed the Lunati Voodoo camshaft ( pn 60334)and slipped it into place. This is a roller cam, so we don’t need any special oils for break-in, one of the great things about roller cams. That said, plenty of lube is still a good idea.
Wow. When the Edelbrock Victor heads (pn 77929)came back from Hughes Engines, we saw how much they reworked these suckers; the ports have hogged out within a micro-inch of their lives, which really increased the flow. A gain of 35 cfm in the mid-range (throughout the full lift range) is a big deal. This is worth a lot of horsepower. As shipped, these ports are rough cast.
We used a cordless drill with the clutch loosened to install the head studs. There are a lot of these and threading them by hand is tiresome. Just don’t tighten them too much. Lots of ARP thread dressing was applied and a set of Fel-Pro head gaskets. All the gaskets used on Evil Betty were from Fel-Pro (Summit Racing kit pn FEL-KS21100).
If you don’t own a speed-wrench, buy one. It is our favorite tool for engine building. We torque the heads to 80 ft lbs from the center bolt outwards. You will want to retorque the heads after break-in.
The Victor series heads have be designed with raised intake and exhaust ports (.650” and .250” respectively) which necessitates offset intake rocker arms. We used this set of roller rockers from Hughes Engines pn HUG 1515S-16). This is not a quick-fit piece, each rocker must be center over the valve stem and then shimmed with .005-.010” side clearance. This takes time and patience. You will be installing and removing the shafts several times during this process. Once set, don’t mess with it.
With the rockers arms positioned, the lifters and pushrods can be installed and the valve lash checked to the specs of the Lunati Cam.
We went with the Milodon external single-line system (oiling kit pn 21010, pan PN 30931). The stock internal oil feed mount should be plugged with a 1\2” pipe plug, which is not included with the kit.
The center-sump oil pan has a hole in the sump where we installed the static pick-up and the -12 elbow. We didn’t tighten this just yet. The kit comes with a pump cover, which mounts to the Melling M63-HV pump.
We moved the elbow on the pump to allow the supplied -12 hose to fit better. A set of AN wrenches is really handy here. The external system amplifies the lubrication potential for the Mopar motor, and the deep sump stays full of oil under heavy acceleration, including wheels-up launches.
We slipped the fabricated Hughes Engines valve covers ( PN PRW 4044007L) onto the heads, installed the Edelbrock intake and valley pan. The valley pan is specific to these Victor heads, a stock unit does not work. Then we installed the oil-pump drive rod.
The MSD Billet distributor (pn 8386) was slipped into the block and engaged with the pump drive. This is just a test fit though, as we will pull the distributor and drive gear to prime the oiling system after the motor is installed in the Scamp.
We also installed the Proform 950-CFM carburetor(pn 67202). The Proform race series is a chokeless design for better flow, has billet metering blocks and throttle bas for reliable power. Best of all, it is USA made. Soon Evil Betty will be pulling the Royal Scamp down the 1320 with brute force.
This is how Evil Betty turned out. Partnered with the Royal Scamp, our duo will soon be out on the town .
A life-long gearhead, Street Tech Magazine founder and editor Jefferson Bryant spends more time in the shop than anywhere else. His career began in the car audio industry as a shop manager, eventually working his way into a position at Rockford Fosgate as a product designer. In 2003, he began writing tech articles for magazines, and has been working as an automotive journalist ever since. His work has been featured in Car Craft, Hot Rod, Rod & Custom, Truckin’, Mopar Muscle, and many more. Jefferson has also written 5 books and produced countless videos. Jefferson operates Red Dirt Rodz, his personal garage studio, where all of his magazine articles and tech videos are produced. You can follow Jefferson on Facebook (Jefferson Bryant), Twitter (71Buickfreak), and YouTube (RedDirtRodz).
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