Anybody who regularly wields a wrench can slam a motor together practically blindfolded. That's the easy part.
If you really think about it, most of the labor is tied up in piecing together the rotating assembly, adding the cylinder heads, and topping it off with the manifold. But if you took a step back and started from scratch, where would you begin? Sure, for the most part our favorite manufacturers are spot-on with their machine work when it comes to engine blocks. However, we're looking to make big power and aren't willing to take any unnecessary chances. When you are in the midst of creating huge reliable strength, why take shortcuts? If you take into account the time and energy, not to mention the cash, that you are willing to throw into your race program, it seems only necessary to have the block machined properly to fit the exact specifications for your application.
This month we left the block in the hands of QMP Racing of Chatsworth, California. Choosing a competent machine/race shop is critical, and over the years we've built good relationships with these race wizards. They've got the know-how to get things done, and they back it up by sponsoring a number of race cars, including a '73 Camaro that recently took a PSCA drag radial championship and an NHRA Division 7 GTO race program. At QMP, expert machinists Mike Consolo and Brad Lagman checked every critical measurements and made sure our tolerances were dead-on. Their combined knowledge was only one reason we chose their shop. They not only facilitate fellow racers with their builds but also utilize an emerging trend and rely on their top-notch CNC machining program, which is where our Dart block was headed. And considering the big plans we have for this Dart block--a monster centrifugal supercharger system--it was vital that we get the job done right first time.
We decided on going for all the beans, pulling out all the stops and getting the block precision-machined with an automated process for much of the work. Our Dart block was delivered to us with a 9.800-inch deck, 4.840-inch bore spacing, and 0.842-inch lifter bores and went through the ringer getting align-honed, decked, bored, lifter-trued, resized lifter bores, and lastly bore-honed with a torque plate. While race shops vary in labor time and prices, we were in and out of the machine shop in a matter of days and spent $1,100 to get the job done. It may seem like a lot, but it's paid insurance and well worth the dough. Plus, when the motor gets put together we won't be running into any problematic issues like the lifters not fitting in the bushings or not having enough clearance for the main bearings once the crankshaft is in. Whether you're into the racing scene or building a boulevard cruiser, any time backpeddling can put a strain on your program.
If you have never seen a block fully machined, it's a sight to behold. Follow along as we take you into QMP's race facility and show you how to get the job done. We show the ins and outs of the machining process, get the scoop on what to look for, and let you know you can expect to pay.
What We Did
Fully machined a Dart Big-M block for big horsepower
What to look for and how much it costs
Starts at $1,100
Like all Dart blocks, our...
Like all Dart blocks, our Big-M block arrived machined, but it's still a good idea to get the block up into the align-hone and measured for accuracy. Mike Consolo led the way, and after learning which crankshaft and main bearings we were using, he started by measuring the mains. Using the bore gauge, he measured each main by checking the front and behind the oil hole, discovering that our mains were 2.936 inches, which is 0.001 shy of what we were looking for. We needed our mains between 2.937 and 2.938 inches. From there, Consolo set the bore gauge to hone the mains.
Align honing can get elaborate,...
Align honing can get elaborate, and costs can be incurred from the extensive labor. Consolo tightened the main caps with oil to 100 ft-lb and loosened them accordingly in order to achieve the 2.937-2.938 inches he was after. Typically, this job alone runs about $140.
Not only are the mains now...
Not only are the mains now properly machined to size, but our main saddles now displayed the textbook crosshatch pattern. This pattern is essential to all bearing seals and oil retention. Plus, it's the sign of excellent machine work.
While most shops don't have...
While most shops don't have a CNC machining program, QMP does--and we took full advantage of it. Javier "Chewy" Dominguez prepared the block by installing the main rings and sliding the main-bar through. He then lifted our Big-M into the CNC machine where we could begin the meat of the machine work.
Once the block is in the CNC...
Once the block is in the CNC machine, Brad Lagman began measuring the block. With the measuring sensor-tool installed and the Dart Big-M program selected, the CNC begins measuring and recording all tolerances and measures everything from deck heights to bore spacing.
The CNC machine begins by...
The CNC machine begins by measuring the deck surfaces and each cylinder bore, all the while recording the information. This ensures that our bore spacing within every cylinder is accurate. The CNC automatically slides the block based on a four-axis program and gently sweeps each key surface point, which also enables it to identify its exact position.