Hell-Raiser, Part 1
Before jumping into Project True SStreet with both feet, much thought went into the engine combination. First thoughts for our '87 Monte Carlo SS had us building a monster Chevy big-block with either nitrous oxide or, better yet, a turbo or two. While the big-block would have shoehorned nicely into the G-body, nitrous can become an expensive habit, especially with a large 300-400hp shot. The bottle would require frequent fills throughout a race weekend.
Having 86'd the nitrous idea, we turned to possibly turbocharging the Monte. Turbo units have become the choice of many racers and street machine owners across the country, because they're easy on parts and they utilize wasted exhaust gases for propulsion. The turbo route was rather enticing, except for the fact that custom exhaust and inlet piping would have to be made to fit our application. They're not cheap, either. Since we're looking to cater to the average enthusiast, we opted to go with a simple supercharger system to propel Project True SStreet into the 8s.
Two types of superchargers came to mind-Roots and centrifugal. Roots-style units look wild and can produce gobs of power and torque out of the gate (low-rpm range); however, they often require hood modifications, never mind the added attention from the local authorities when cruising Main Street USA. After putting in a call to the extremely helpful staff at ProCharger, we decided to utilize its F-2 intercooled supercharger system, which comes complete with all that is necessary for a hassle-free installation. Oh yeah-it will also make some serious power to boot. More on the supercharger in Part 2 of "Building a Hell-Raiser." For now, let's get into the strength of the foundation needed to keep Project True SStreet together.
The Little M block from Dart comes almost ready to roll; however, it will need a finishing hone, as well as a custom finish specified to the builder's liking. The main objective is to leave the cylinder walls as straight as can be and to provide the proper amount of crosshatch, which will offer proper oil retention and ring support. Incorrect crosshatch can lead to premature wear of the piston rings, possibly causing compression loss or even oil blow-by. Here, Ron Ross of Simonek Performance Machine (a division within M2) puts the finishing touches on our Dart block with a Sunnen CK-21 digital honing machine. The block retains the main caps and receives a torque plate to maintain proper geometry as if the engine is assembled. Before the block is dismounted, Ross uses a bore gauge to make sure all is within specified value (4.126-inch bore finished).
As previously mentioned, big-block power was in the plans during the early stages, but it was scrapped in favor of a lighter (lighter is faster) small-block. With today's technology, it's not unheard of to make 1,000-plus horsepower with a ProCharged small-block Chevrolet equipped with proper components. Since we will be running a 28-inch DOT tire out back, the torque of a big-block, coupled with the added horsepower of the juice or turbo, may have prevented a problem with keeping the tires planted on launch. Running a small-block with a centrifugal blower will generally allow us to have a larger power gain toward the middle and top of the rpm range, enabling the G-body to produce slightly less shock to the tire on launch, hence achieving hook, with the added feature of having less weight on the nose.
Once the block is completed, Ross hands it off to engine builder/racer Anthony DiSomma of M2. Before any building can begin, the block must be thoroughly cleaned. This includes all oil galleys, coolant passages, and any other exposed orifice. After the cleaning process is complete, the block gets blown out with compressed air and is mounted to an engine stand. At that time it is rolled into the engine assembly room, which is generally the cleanest area in the shop. Surgery/construction may now begin.
Shown in the image on the left is a four-bolt main from a stock 400 block, and on the right is our Dart unit. The main difference is that the stock unit utilizes a straight-down, parallel fastening configuration for the main caps, which puts a ton of load on the block's main section. The Dart unit utilizes a splayed fastener on the outer portion, putting stress into the more beefy area of the casting, creating a stronger clasp and deterring the main cap from walking (moving under load).
To anchor the foundation, we called upon Dart Machinery in Troy, Michigan. The professionals at Dart suggested the Little M block, which is a high-performance block that can be used with standard off-the-shelf (stock-type) SBC components. The Little M is cast from high-strength iron and beefed up in critical locations where a stock block would normally fail. We opted for the 4.125-inch bore with SBC 400 mains. Now all we need are the components to aid in assembly of the bottom end.
For the rotating assembly, we called upon the folks at Lunati in Olive Branch, Mississippi. Lunati has been known for years for providing racers with quality crankshafts, connecting rods, camshafts, pistons, and valvetrain components. Lunati is under new ownership, vowing to return to its roots, supporting racers like never before. After conferring with the technical specialists at Lunati, we decided to build a 400ci small-block. For this we will employ Lunati's fully machined 5.7-inch connecting rods, Pro Series-4340 forged steel crankshaft with 3.75-inch stroke, and a custom set of forged Pro Tru Wiseco pistons with a -20cc reversed dome (dish) for lower compression. Blower engines require a lower engine compression to operate safely. Forced air into the cylinder can create disastrous results due to higher cylinder pressures if the combination is not correct.
As with any build, camshaft selection is critical-more so when you are looking to make over a thousand streetable horsepower. After discussing camshaft options with the staff at ProCharger, it was suggested that we give Steve Morris Racing Engines (SMRE) in Muskegon, Michigan, a buzz. Steve builds some crazy ProCharged combinations that lay down serious horsepower. It is not uncommon for SMRE to build a 1,000-plus-horsepower ProCharged SBC to run on pump gas with hydraulic lifters.
With this kind of knowledge and experience building ProCharged blower combinations, we decided to score a custom solid roller bumpstick from SMRE with a conservative lift of 0.668-inch on the intake and 0.672-inch on the exhaust. Duration checked in at 264 on the intake and 272 on the exhaust. Normally one would think the more lift the better when making power levels as such, but with the progression of camshaft technology, that is not the case.
DiSomma now checks the diameter of the crankshaft mains via a micrometer. This is critical when determining the main bearing clearance, as well as checking the uniformity of the crankshaft grind. Once the crankshaft is measured, a bore gauge is employed to measure the main bore, but not before the main bearings are installed and the caps are torqued. Once the measurements are calculated, the bearing clearance can be obtained. We are looking for a main bearing clearance of 0.0030-0.0032-inch. While this is slightly larger than the standard passenger car, it will be fine for our blown mill, which will utilize a thicker oil than normal. Thus far all measurements have checked within range.
To take charge of the valvetrain, we called upon Comp Cams in Memphis. Comp has quite a selection when it comes to valvetrain components, so it is recommended that you contact one of its technical consultants for assistance, as we did. Comp suggested we utilize its Hi-Tech Belt Drive system to keep the crankshaft in check with the camshaft, aiding against valvetrain instability. We will also be using rocker arms, solid roller lifters, and pushrods from Comp, which will be introduced in Part 2.
To build our True SStreet small-block, we called upon Ron Mielbrecht and the staff at M2 Race Systems in Farmingdale, New Jersey. M2 can do it all: engine machining, assembly, cylinder head service, and its mainstay, five-axis CNC machining to port cylinder heads, as well as aftermarket custom pieces. M2 caters to major manufacturers in the industry, and we are happy to have them aboard Project True SStreet.
Now stay tuned as the professionals at M2 Race Systems get busy with our blower-specific short-block.
The main bearings are coated with assembly lube and the crankshaft is temporarily installed along with one piston and rod. This step is critical in checking the deck height (the relation of the block deck to the top of the piston) at all four corners of the block. This measurement will also verify that the deck surfaces are true from front to back. All was within specification. Deck height checked in at around 0.010-inch in the hole (below the deck of the block).
Now DiSomma installs the coated camshaft bearings, which are provided from Dart upon purchase of the block. A special camshaft bearing installation tool is used to press each bearing into its respective location, starting from the rear forward. The bearings can't just be slapped into place-they must be lined up with the oil galley in the main, as well as the outer bearing groove. A small flashlight can be used to peer into the hole for alignment verification.
Now that we are confident that no further machining is required on the block, the crank is removed and the block is painted to protect it from the elements. DiSomma then presses in brass freeze-out plugs and plugs off all the external oil galleys. The Dart block contains 1/4-inch provisions within the lifter galleys, both in the front and rear to block off oil feeds. DiSomma blocked off the lifter galley feeds in the front of the block just above the front camshaft journal, thus allowing oil to feed from the rear and deadhead. Why? Since we are using solid roller lifters and a Moroso race pump, less oil is required (as opposed to a hydraulic lifter). This will keep the oil in the bottom end where it's needed the most. Additionally, the Dart block features priority main oiling, feeding the crankshaft before the top half of the engine.
Once the camshaft is carefully inserted into place and checked for binding and alignment, DiSomma reinstalls the crankshaft. Once the crankshaft and mains are in place, the inner fasteners are torqued to 65 lb-ft and the outers to 35 lb-ft as specified by Dart.
Beyond torquing the mains, the crankshaft endplay must be checked (the movement of the crankshaft from front to back). DiSomma usually likes to see movement kept between 0.004-0.007-inch-ours checked in at 0.007-inch, which is within specification. It is now time to install the Comp Cams beltdrive (PN 6500) onto our little hell-raiser. This unit is bolted into place as easily as a stock timing would be.
After the main body is installed, the camshaft's endplay/thrust must be checked. Comp specifies that it should be between 0.002-0.007-inch. The thrust can easily be adjusted using the beveled retention plate shown. Adjustments can be made in 0.0025 of an inch. Once the thrust is set, the adjustable camshaft sprocket and belt can be installed. With the belt and unique idler, the Comp Cams beltdrive will help stabilize valvetrain harmonics and keep our timing in check.
DiSomma will now assemble the Wiseco pistons to the fully machined 5.7-inch Lunati connecting rods via the wristpin. In order to secure the wristpin in place, Spiro Lox are used. Spiro Lox are similar to a tightly wound Slinky and are carefully inserted into the groove machined in the piston. Beyond the assembly of all eight pistons and rods, the piston rings are filed to the builder's specification. In this case, the top ring is gapped to 0.030-inch and the second to 0.034-inch. While most engines require a tighter gap, blower engines generate more cylinder pressure, thus increasing heat. Therefore, a larger gap is used to deter against ring butting (closing of the gap). All rings should be checked using a feeler gauge in its future respective cylinder.
Next, the piston and rod assemblies are installed into the block utilizing a tapered ring compressor and the butt of a rubber hammer. Take note that the connecting rods are beveled on one side. This beveled edge should point toward the end of the crankshaft journal (putting the non-beveled edges of the rods together). The connecting rod end caps are then torqued.
With a myriad of tough components and a compression ratio of approximately 8.9:1, our blowerspecific bottom end is now complete and ready to receive additional components from Moroso, Air Flow Research, ATI Racing, Edelbrock, The Carb Shop, Holley, Fel-Pro, and more. So stay tuned for Part 2, as we try to get this baby completed and fired up on the engine dyno. Early speculation has us checking in at around 1,300 hp with highoctane race gas, but we'll see.