5.0 Mustang & Super FordsHow To Engine
Boss 340 Dream Engine Build - Born-Again Boss
After Months Of Planning, Probe Industries Makes Our Boss 340 Engine Dream A Reality
Horse Sense: For the uninitiated during the last few months we've been working on producing the first true fuel-injected Boss-style engine based on Ford Racing Performance Parts' Boss 302 block. When it comes to Mustang engines, daring to go where no 'Stang mag has gone before is the type of challenge we're always up fore. Remember: We dig horsepower, which is one of the keys to making Ponys run hard. We also appreciate knowing what you, our readers, think are cool engine combinations for Fox-though-S197 'Stangs, so give us your thoughts!
Building the first version of our old-school/new-school Boss engine has been a great experience thus far. Through our coverage of the engine's development, we hope you're gaining a better understanding of exactly how special both versions of our bullet really are.
The Boss 340 will be loaded with a hydraulic-roller cam/Edelbrock head package first, and then a solid-roller/Air Flow Dynamics setup for racing. In this huge world of bolt-on parts, our attempt at mating Cleveland-style (canted-valve) cylinder heads on the surface of the new FRPP 8.2-deck block is major. That's mainly because we're once again challenging the aftermarket to acknowledge the fact that enthusiasts will sometimes consider going way beyond what's considered the norm when it comes to making their Mustangs special.
Our first article ("The Comeback," Feb. '08, p. 82) focused on the preparations that were necessary. We detailed L&R Automotive's procedures for machining the block, enlarging its bores to 0.100-inch over their 4.000-inch standard size. The second ("True Identity," Apr. '08, p. 107)centered around the parts that will comprise both versions of the Boss 340.
With all the pieces in place, we're now at a point where we can actually build the long-anticipated engine. Assembly is taking place at Probe Industries in Torrance, California, and the company's senior engine assembler is handling the job.
The following is a pictorial breakdown of how a canted-valve, EFI, true Boss engine comes together. Remember, this bullet's (and the one that follows it) mettle will be tested on the engine dyno as well. We suggest you make sure your subscription is current to keep from missing future reports, as well as the data we gather from a project that will take us farther into unknown territory as time goes on.
The back-and-forth movement of the crankshaft is commonly referred to as its endplay. It's measured by positioning the probe of a dial indicator on the crankshaft snout and moving the crank back and forth in the saddle. The thrust bearing and main cap must be installed and torqued to spec before recording this value. Probe accepts no more than 0.009 inch (0.007 inch is preferred) of endplay for all of its small-block engines. Once endplay is dialed, the main caps are torqued to spec (100 lb-ft for the 1/2-inch bolts, and 45 lb-ft for the 3/8-inch bolts on the outside of each four-bolt cap).
These are the lightweight, 5.400-inch, forged I-bean rods and flat-top pistons that are being loaded into our Boss 340. While 0.100-inch 351 Cleveland pistons aren't shelf items at Probe, shop foreman Shawn Mendenhall designed slugs for our bullet that were made in-house, and feature 0.025-inch deeper (intake) valve clearance when we swap the heads/cam/intake package in the second phase of our project. We're using Total Seal's Classic Series race rings to maintain steady combustion inside the Boss 340.
We're building one short -block for two versions of our Boss 340 engine, and its central component is this forged-steel crankshaft. Probe uses a 3.250-inch arm for its popular Street Fighter stroker combinations, which are similar to ours.
This new digital cam-degreeing tool is beyond cool. We got our first look at CamLogic Technologies' digital degree system at the '07 SEMA show, and we knew it would be perfect for this and future engine projects. After getting CamLogic set up, rotating the engine clockwise, and storing BTDC and ATDC values using the system's digital display, the tool accurately identified true TDC for our Boss 340. We then went on to put CamLogic to the true test-degreeing our hydraulic-roller cam-and it performed like a champ. Based on our start-and-stop measuring positions, before and after 0.580 on the intake side, CamLogic's display reads 107.75 degrees, which is almost spot-on with the 108-degrees, which is almost spot-on with the cam card. The procedure is the same for a com's exhaust profile. Sure, the info is attainable with a degree wheel and a calculator, but this tool definitely makes it simple.
The keys to installing 351 Cleveland heads on a 302 block are making sure the water passages on the surface of each head are plugged, and passages are created (holes drilled) in the appropriate sections of the intake deck. We made the necessary modifications, but a discovery in Edelbrock's '08 product catalog proved to us we were slightly ahead of our time when we conceptualized our project. We mentioned Edelbrock's new E-Boss 302 intake manifold in our last story on our engine and explained how its unavailability led us to seek the assistance of Wilson Manifolds to create the Boss intake we're using. Well, Edelbrock has further simplified building a Boss-style 302. The company's new Performer RPM Cleveland heads (PN 61699; $979.99) mate perfectly with the E-Boss intake and are configured for 8.2-deck blocks. The eleventh-hour machine work we had to do isn't necessary with Edelbrock's matched set, but after overcoming the anxiety brought on by the need for custom work, it was fun figuring out how to make things right for our Boss 340.