SHORTBLOCKING A SCAT STROKER KIT FOR 505 CUBIC INCHES OF HOT STREET/STRIP POWER
By John Baechtel

Part 1 of our Mopar 440 stroker build shows the steps we took to build a robust short block to support 505 cubic inches with a Trick Flow Specialties top end kit that includes fully CNC'd 270 Powerport cylinder heads, hydraulic roller camshaft, Track Heat single plane intake manifold and a 950 CFM Holley Classic HP carburetor. The intent is to illustrate the power potential of Trick Flow's dedicated top end kits. To build a solid foundation for a hot street/strip engine  we chose a SCAT balanced rotating assembly that includes a forged 4.250-inch stroke crankshaft, 6.8 inch big block Chevy rods, a precision machined set of Diamond forged pistons and Total Seal's new gas ported piston rings.

At the end of this story, you'll find a comprehensive parts list with direct links where you can buy all of these part directly through Summit Racing. Using top quality parts and  meticulous machine work performed with our preferred local engine shop, Basham Motorsports in San Bernardino, CA we're hoping to push close to 700 horsepower for a 1974 Cuda that will see dual-duty on the street and strip along with car show appearances. Despite the current pandemic and current difficulties in getting parts, Summit provided exceptional and speedy parts delivery to keep this project moving forward.

 A standard bore, crack-free Chrysler 440 cylinder block removed from a low-mileage motor home is the basis for this build. It cleaned up well and revealed the stout, but less than world class casting quality typical of its era. The first step was to prep it for Milodon's new cross-bolt  Extreme Duty Maincap kit which includes five billet steel caps capably installed and line-bored by QMP Racing Engines in Chatsworth, CA.  Click here to see the maincap installation story.  Milodon Maincap Install

The Diamond pistons in the SCAT rotating assembly are .030-inch oversized and they all measured  exactly as specified. Per instructions, we set the piston to wall clearance at .0045-inch.

After boring the cylinders, the head bolt holes are cleaned with a thread chaser in preparation for installing the BHJ torque plate for final honing.  A Cometic C5462-040 MLS Head Gasket from Summit was used under the torque plate. We ordered three as the torque plate gasket was sacrificial and we would need two uncrushed ones for final assembly.  These multi-layered-steel gaskets crush to .040-inch thickness and have a 4.410-inch bore diameter. Although the engine bore size is 4.350, you cannot use a MLS gasket of the same size as it will crush into the bore and interfere with the honing stones. As shown here, the block was then checked for its current deck height and the stack up of stroke, rod length and compression height was calculated to determining the cut for decking the block.

Multiple small deck cuts are made to sneak up on the desired deck height and establish the mirror smooth finish required for MLS head gaskets. The factory deck height on a Chrysler 440 RB block is 10.725-inch. This block measured slightly taller. Our component stack incorporates rod length, one half the stroke length and the compression height for a total of 10.705-inch. So we cut the decks to achieve a positive deck height of .005-inch. With the compressed Cometic head gaskets at .040-inch we achieved our desired piston to head clearance of .035-inch. After decking, the head bolt holes are chamfered and the entire block is carefully deburred.

Basham Motorsports likes to deburr all the cam bearing housings and they made their own tool which allows them to pull the bearings into the bore instead of pounding them in with a regular cam bearing tool. Here you can see the threaded mandrel pulling the cam bearing into the housing bore as the handles on the tool are turned.

The Speed Pro cam bearings from Summit Racing installed with no issues. A view from the main bearing saddle shows the cam bearing hole perfectly aligned with the oil passage.

To protect the cam bearing housing bores while painting the lifter gallery, roll up an old poster or something similar and insert it through all the cam bore. Roll it tight and allow it to unwind once in place. We used some home made lifter bore plugs to protect the lifter bores from over spray and masked off the machine surfaces to protect them while spraying with red electric motor insulating varnish.

SCAT stroker rotating assemblies for Mopar RB engines are available in several configurations based on your desired stroke length up to 4.250-inch. You also have a choice of pistons that SCAT will include in the kit.  We selected a forged 4.250-inch stroke with an upgrade to forged Diamond pistons. These cranks are fully machined and the crank journals measured spot on as advertised. The crank also incorporates a generous radius on the front snout. It is basically a Hemi crank with an eight bolt rear crank flange.

The Diamond pistons are forged 2618 alloy shelf-stocking units with a 24cc dish and a 1.78-inch compression height. They use a .990-inch wrist pin to fit the Chevy pin bore size on the 6.8-inch SCAT connecting rods. Specs were right on as advertised, but due to our cautious nature, we opened up the pin bore by another 3 tenths. The big end of the rod matches a big block Chevy journal size and the rods are fitted with ARP 2000 high strength cap screws. We have used these rods in other builds and they have always performed well.  See the links at the bottom of this story to find these parts at SCAT.

Total Seal's new gas ported piston rings are a great choice for this application. We used a Total Seal ring squaring tool to measure the ring gaps in the cylinders. The gas ported top rings are gapped at .020-inch and the second rings are set at .024-inch. While the traditional file fit technique is still a valid method, we used an ABS electric ring filing tool. These tools have pegs to help you keep the ring face square to the grinding disc and a dial indicator to show you how much material you are removing. Finally, the rings are installed with Total Seal's ring spreading tool.  They advise against ever spiraling rings onto pistons since it can weaken the ring and upset the built-in twist that allows the ring to function properly.

Here David Basham is checking main bearing clearances. We set the mains at .0021-.0023-inch, the rods at .002-inch and the crank thrust at .007-inch.

The Diamond pistons utilize double Spirolox on each end of the piston pin. They are not that difficult to twist into place, but care must be taken to make sure you don't leave one out. This is a common mistake. When installed correctly the pin does not move and it allows minor movement of the rod on the pin. Note the pin oiling hole in the SCAT connecting rod.

With the crank installed, the maincap studs are torqued to Milodon's recommended 85-90 lbf-ft. The cross bolts are torqued to 35 lbf-ft. Total Seal's 4.350_inch tapered ring compressor is used to push the pistons into the bores. ARP's fastener assembly lube is applied to the  threads on the rod cap screws and also the bottom of the bolt heads. Below is the complete SCAT rotating assembly installed in the cylinder block.

Using a mix of parts from different manufacturers often leads to component fitment issues. This isn't the fault of any particular manufacturer as they try to make their parts as compatible as possible. In this case we're using a CVR two-piece billet timing set which allows us to make camshaft changes without disturbing the seal at the oil pan.  We found that the heads on the ARP cam bolts were too tall and would not allow the cover to seat fully and compress the O-ring seal. We tried a different set of ARP cam bolts with shorter heads but it still wasn't' enough. The center photo shows the tall cam bolt farthest from the center on the left. The two nearer bolts have the shorter heads.  Trick Flow's cam gear rides on its own shim and we determined that there was enough thickness to the gear that we could countersink the holes to accept the shorter ARP bolts.

Commercially available cam buttons did not offer the camshaft thrust clearance we wanted once the timng cover was secured in place. Because we are using a retro-fit hydraulic roller camshaft we have to limit camshaft thrust movement to the minimum possible; .003-inch in this particular case. We don't want the camshaft moving back and forth under the roller lifter wheel. So David Basham fired up the lathe and machined this cool little Delrin bushing to the exact dimension we required. It will never wear out and it gave us the exact thrust we wanted.

The Trick Flow double roller timing set is fully adjustable via the crank gear. The straight up position is marked by the "zero" on the inner radius of the gear. It must be installed aligned with the crank keyway. The outer markings are used to align with the crank gear. Note the "zero" on the outer radius of the gear.  This is what you line up with the dimple on the cam gear. That is the TDC position for cylinder number six. When the crank is rotated and both marks are at the top, it is the TDC position for the number one cylinder.  We used our favorite tool, the Altronics Digital Degree Wheel and a dial indicator tool in the lifter bore to degree the cam. The spec called for 104 degrees and we hit pretty close at 103.5 degrees right out of the box. If, for example you want to advance the cam, say two degrees, you would line up the A2 on the inner radius above the crank keyway and align the dimple on the cam gear with the A2 mark on the outer radius of the crank gear.

Here's the cam card for the hydraulic cam Trick Flow specified for this build. Could you make more power with a bigger custom grind cam? Probably, but these are off-the-shelf components and this is enough cam to put you well over 600 horsepower for a hot street/strip combination. The 270 PowerPort CNC'd heads will support more power if that is your goal. There are lots of ways to build one of these, but this is a great combination for the home builder and it will still work well with a moderate torque converter and rearend gearing in a street/strip application.

An ATI Super Damper is always a great choice for this type of build and we noted some important considerations when installing a balancer. First, don't assume absolute compatibility across different product lines. Always measure the crank snout and compare it to the inside diameter of the damper hub. Read the instructions and make sure your measurements are compatible. In this case, the ATI damper matched the SCAT crank snout perfectly and a damper installation tool was used to pull the damper hub onto the crank snout.  Two different balancer bolts are available from ARP. You must use the shorter bolt seen here on the right. It is compatible with thin dampers like the ATI unit while the longer bolt is required for thicker OEM style dampers.

Milodon's Pro Touring oil pan incorporates its own dedicated pump pickup and windage tray. Although the blocks are nearly identical, the pickup uses a 3/8-thread instead of the 1/2-thread used on a Hemi block . It is secured by a dedicated bracket anchored on an adjacent main stud. It also has a strap over the pickup screen to make certain it never bottoms on the pan to restrict oil flow. The windage tray is a full length piece that gets captured between the block and oil pan rails. It required minor grinding near the pickup opening to fit through it, You have to rotate the tray 90 degrees to the block, insert the pickup tube through the rear opening and screw it into the block while manipulating the tray slightly. Once the pickup tube  is tight in the block, the pickup itself sits level and the pan can be installed. Two gaskets are required.

The Milodon Pro Touring oil pan is a low profile center sump with side kickouts that are perfectly suited for the 1974 Cuda this engine will reside in. Note the Milodon freeze plugs and core plugs and the crossbolts for the main caps on the side of the block. Up top, the 24cc dish Diamond pistons yield 10.6:1 compression with the CNC'd Trick Flow 270 Powerport heads we will install in part two of this build.

We chose to use a CVR two-piece timing cover, not just for its good looks, but because it permits easy cam swaps or timing adjustments without disturbing the front seal to the oil pan.  It comes with a super trick timing pointer specified for the diameter of our ATI Super Damper. To complement it we added CVR billet fuel pump block off plate as well.

Johnson Lifters hydraulic lifters are our first choice for their high quality and precision metering on a hydraulic roller cam. Their 2312BBR lifters call for .035-inch preload, plus or minus .010-inch. We have found that these lifters maintain more consistent valve action over time and they provide troublefree operation thanks to full axle oiling and close tolerance internals. We'll see more of these in part two as we perform pushrod length checking.
Depending on your requirements you can build this bottom end to a greater or lesser extent and to generate more or less power based on your cylinder head, camshaft and induction choices. You can also spend more or less money. Your choice. This is a pretty robust combination that will rely on increased displacement, moderate compression and cam timing, a great set of cylinder heads and a single four barrel carb. In the Cuda it will be backed up by a 727 Torqueflite trans and a converter yet to be determined. The goal is a pump gas friendly cruiser that will see street use and occasional drag strip duty.