Boss 340 Dream Engine Build - Born-Again Boss

Ford Racing Performance Parts' 351 Cleveland valve covers (PN M-6582-A341R) and oval-shaped air cleaner (PN M-M9600-K302) add a classy final touch to our completed Boss 340 project engine.

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.

After a meticulous prep job by the crew at L&R Automotive, our project engine's FRPP Boss 302 block (PN M-6010-BOSS302) gets a few fresh coats of high-gloss black engine paint before it's rolled into the assembly room at Probe Industries.

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.

We can't stress enough the importance of clean when building an engine. Probes's assembler sprayed each cylinder with brake cleaner, then used a paper towel to wipe down the holes, ensuring they're free of spray-paint residue or other foreign matter before installing the hard parts.

Here's a look at the character trait that makes the new Boss block a sound choice for a 302-based stroker engine. The block features nodular-iron, splayed, four-bolt main caps on the main journals of numbers two through four. With its Siamese-bore configuration, there's boatload more material between the cylinders, which leaves a lot to the imagination as far as mega cubic inches are concerned.

We selected Clevite 77's bearings for our Boss 340. Once the set is installed, Probe's assembler coasts each bearing with Pro Blend Assembly lube. The lube eliminates friction between the crankshaft journals and main caps, as well as at the crank and rods.