True Identity - Boss 340 Engine Build, Part 2
Horse Sense: In order to meet the SCCA's minimum requirement for eligibility in its Trans-Am racing series, Ford had to produce 1,000 Boss 302 street Mustangs in 1970. We've heard off-and-on musings about Ford possibly building a new Boss 'Stang (remember, the S197 is scheduled to undergo an appearance makeover in 2010), and while we honestly don't know anything official about a return of the Boss, we can't stop thinking about how bad it would be after more than 30 years of advancement in Mustang performance.
Based on feedback we receive via the Internet (e-mail, message forums, and so on) and in person, we think it's fair to say that many of you get with 5.0 Mustang & Super Fords each month to find out the latest on our various projects-large and small. We truly appreciate your loyalty to our mag, and hope that the broad range of subjects we cover for Fox-thru-S197 Mustangs is informative and encourages you to use the bolt-on parts we install in Mustangs, or the engines, transmissions, and other driveline pieces that we profile.
When it's all said and done, conceptualizing and making bad 'Stangs and pushrod or modular engines of all dimensions and performance levels are the main ideas that spin the revolving door of our cool projects. Our latest engine effort is a prime example.
If you're just joining us, last month we introduced our newest project ("The Comeback," p. 82, Mar. '08): creating a modern-day EFI Boss engine based on Ford Racing Performance Parts' new Boss 302 block. It will feature canted-valve, Cleveland/Boss-style aluminum cylinder heads from Edelbrock and Air Flow Dynamics. Using inline-valve heads has been a longtime standard of sorts for magazine engine builds, but we think the time has come to finally do something different.
What do we mean by "different," you ask? How about employing a radical alternative to inline valve heads on a Mustang powerplant that goes far beyond the accepted norm for 5.0-based street and race engines, and at the same time, pays homage to one of the baddest bullets in Ford-engine history. We realize old-school Boss 302 purists may not take too kindly to what we're doing, but to them we say, "Get over it."
In Part 1 of this series, we focused on the surface details of the engine's makeup and L&R Automotive's meticulous preparation of our FRPP Boss block. In this installment, we take a closer look at the actual hardware that comprises our Boss 340-especially the cylinder heads and intake manifolds, which are above and beyond those found on other 5.0 strokers.
This second leg of our effort took us to Probe Industries in Torrance, California, where our L&R-prepped block was waiting on an engine stand when we arrived. Probe's shop foreman, Shawn Mendenhall, has choreographed a thorough assembly plan for our Boss 340, which we will chronicle right here in these pages.
While we realize Roush now offers Cross-Boss 351R, a fuel-injected, 351ci version of the modern-day Boss engine, we're the first 'Stang mag to build one. So for now, read through the following captions as we forge ahead with this groundbreaking project, preparing our rev-happy engine for dyno flogging and installation in a full-on drag race Mustang sometime in the not-so-distant future.
Before we get into the "new," here's some more of the "old" for you. Sewer-like 2.5-inch intake ports and a canted angle on the 2.19-inch intake valves (1.71 exhaust) are two of the main characteristics that make Cleveland heads so special. Think about this in relation to the 2.08/1.65 valve sizes that have been thought of as "big" for small-block cylinder heads-for about as long as 'Stangmania has existed. The only way to fit valves this large in a cylinder head is by installing them in canted arrangement. OG Boss 302 heads, circa 1969, actually sported gargantuan 2.23-inch intake valves and closed 62cc "quench" combustion chambers, which made the 'Stang a gangster on the street. In 1970, Ford downsized Boss intake valves to 2.19 inches and reduced chamber size to 57cc.
We're closing off our engine with this aluminum Fox Drag Pro Power oil pan kit from Canton. The set features the 9-inch rear-sump pan, which includes an interior steel girdle, a pickup, and a universal dipstick kit.







Pistons are among the many hard engine parts that Probe Industries specializes in. This run of slug stock isn't for Boss 340s, but Shawn Mendenhall says Probe's CNC machines have the capability of quickly producing dozens of flat-top pistons that will work in new Boss engines.






As you already know, our Boss is based on Ford Racing Performance Parts' Boss 302 engine block. The block was bored .100-over by L&R Automotive, and will be loaded with this 3.250-inch forged crankshaft/5.400-inch lightweight I-beam rod combination from Probe Industries.






Shawn uses a proprietary engine-spec program to determine exactly "how big" an engine will be, based on its internal makeup. Our Boss bullet will displace 340 cubes, at 10.5 to 1 compression with the Edelbrock 2V heads and 11.5 to 1 compression with AFD's 4Vs (for those who have always wondered what "2V" and "4V" mean, the numbers 2 and 4 represent the total number of venturis/barrels in a carburetor). With the compression difference and a fuel difference, we hope to see the engine make 450 or so horsepower on pump gas, and just about 600 horsepower when race fuel is flowing through the Boss 340.
Here is a closer look at one of the pistons that will fill the project mill for our Boss application. Probe's Cleveland flat-top will have a 4.100-inch diameter. Shawn is moving the top ring down on our slugs (from 0.320 inch to 0.360 inch) to facilitate our probable use of nitrous as we go about testing the engine.





Fel-Pro gaskets seal the deal for our Boss 340. Shown in this group are the standard-bore 1021 head gaskets. The project engine has a bigger bore and will probably be treated to a dose of nitrous at some point, so stepping up to Fel-Pro's 1134 PermaTorque MLS (4.180 bore size) is required.





Here is a breakdown of the critical data for original steel, canted-valve, Cleveland-style Ford heads and the two flavors of new-school aluminum heads we'll be testing. Small combustion chambers, large ports, and big valve sizes make Cleveland heads a great choice for street or racing applications, which is one of the reasons Clevor or Windcleve engines (Cleveland heads on 9.5-deck, 351W-based short blocks) are so popular among hard-core 'Stangbangers.
Note the info on the Aussie 302C. This head is considered the poor man's substitute for Boss 302 or 4V Cleveland iron heads. Despite their small (but canted) valves and relatively tiny ports (for street efficiency), 302Cs sport 57cc closed quench chambers that significantly boost compression. Before the advent of aluminum heads, the Aussie 302Cs were great bang-for-the-buck alternatives to the big-port 4V pieces. They were relatively inexpensive and worked well enough to jack compression on a stock 351C to the point where using high-octane fuel was a must.
&nbspChamberPortIntake ValveExhaust Valve'70 Boss 30257cc/ClosedLarge2.191.71302C Aussie 2V57cc/OpenSmall2.051.65351C 4V62cc/ClosedLarge2.191.71Edelbrock Cleveland 2V60cc/ClosedSmall2.051.60AFD SP4V62cc/ClosedLarge (Raised)2.191.65
We spent a lot of time studying the cylinder heads that will adorn our Boss 340.
Again, our plan is to use the same short-block and develop two versions-one street and one hard-core strip-of the bullet. Edelbrock's Performer RPM Cleveland 2V cylinder heads and Air Flow Dynamics' SP4V castings are basically the stars of the show.
We can't compare heads, as they're truly night-and-day different in design (with the exception of sharing canted valves), and especially in purpose. When combined with a 0.580 (intake)/0.577 (exhaust) hydraulic-roller camshaft from Comp, our Edelbrock heads should turn our engine into a solid 400hp street player. On the other hand, there's really nothing "street" about AFD's killer hunks of aluminum. Once we mate that head package with Comp's solid-roller camshaft-0.770/0.773-the Boss 340 will almost certainly zing much higher in rpm and pump out close to 600 horses at the flywheel.
We clearly have two types of 351C cylinder heads that will work well for their respective applications. Be sure to stay with this series, 'cause it's definitely gonna be a good one.
Despite their small valve size-by Cleveland's standards (2.05-inch intake/1.60-inch exhaust), Edelbrock's Performer RPM 351C 2V heads feature closed 60cc combustion chambers. We found it interesting that the slight shrouding in the chambers of these heads is more prevalent over the intake valves than the exhaust.








Edelbrock's exhaust ports are square and 90ccs in circumference.












The Air Flow Dynamics SP4Vs have a 62cc closed chamber profile, in which the head surface just slightly shrouds the exhaust valves. Increased quench area allows for a more complete air/fuel burn, and thus, greater torque production with much less timing than required for max power and efficiency with the original Boss or 351 Cleveland engines.







AFD's owner, Dave Webb, says the exhaust ports on his heads are heavily modified (widened and raised 0.080 inch) in order to increase flow throughout the lift range. "On the exhaust side, lower lift flow is actually more important than high-lift flow," Dave says. "Testing various flow levels has proven that low-lift exhaust flow alters the torque curve dramatically. The more that exhaust flows between 0.100 and 0.400 inch, the more the torque curve responds-for the better." Despite the increase in port height, the heads don't require custom or one-off headers-a big plus for our effort.



We're adding this photo to demonstrate an example of open-chamber cylinder heads. This open-chamber, high-output Cleveland head was installed on the optional 277hp, low-compression 351 engine ('72-'73 Mustangs). Notice how the combustion chamber is circle-shaped and doesn't shroud the valves? On a stock engine, this chamber is exactly the same diameter as the cylinder bore.
Here's a comparative look at our Edelbrock Performer RPM Cleveland 2V heads (right; PN 61629; $975/pair) and Air Flow Dynamics' new SP4Vs ($1,250/bare). While both sets of heads are available already assembled (Edelbrock includes stainless valves, 1.540-inch double springs, stud-mount rocker hardware, 7-degree locks, and chrome-moly retainers), our AFD heads were tricked out with Manley Race Master valves and valvetrain components from Comp Cams that include high-bling, 1.650-inch triple valvesprings (PN 947-16); 11/32 super locks (PN 611-16); and 1.625-inch super-lock retainers (PN 739-16).
Check out the night-and-day difference in location and shape for each intake port. Edelbrock uses a rectangular shape and standard location for its 190cc intake runners, which is essentially close to that of a 302C 2V head. On the other hand, we measured and found Air Flow Dynamics' intake port to be approximately 0.575 inch higher than the Edelbrock with a much larger (230cc) circumference. "Air basically flows across the roof of the runner," says Shawn Mendenhall of Probe Industries. "By bringing the floor up, Air Flow Dynamics essentially got rid of all of the dead space at the bottom of the runner that Clevelands typically have. Air has a straight shot into the chamber."
These are the parts that highlight the Comp Cams hydraulic-roller camshaft setup we're using in Phase 1 of the Boss 340 build. The cam (PN 35-000-8; grind number FW 3017F/3038F) weighs in with 0.580 (intake)/0.577 (exhaust) lift and 0.236/0.242 duration at 0.050, with lobe separation measuring 112.0. Pro-Magnum retro-fit hydraulic lifters (PN 8931-16) and a billet timing-chain set (PN 7138) complete the compilation.



On the solid-roller side, we have a huge bumpstick lined up for the AFD-headed version of our Boss. This billet cam, also by Comp (PN 35-000-9; grind number FW 2231F/2233F), features 0.770 (intake)/0.773 (exhaust) lift and 0.270/0.274 duration at 0.050. The lobe separation for this cam is also 112.0. Solid-roller lifters (PN 838-16) will be swapped in, and the same timing-chain set will work in this version.




A set of Probe Industries stud-mount, aluminum 1.6-ratio roller rocker arms will handle opening and closing events for the valves on the Edelbrock-headed Boss...








...and valvetrain stability is maintained with shaft-mount rocker arms when revs spin higher with the AFD setup.









Ultimately, acquiring the correct intake manifolds for our special small-block was the most difficult task in our project plan. Remember, we're building an engine that technically hasn't been done before, so naturally the aftermarket doesn't have an abundance of intakes available for us to choose two that suit our needs. Edelbrock's new Performer RPM E-Boss intake for carbureted 302 engines (PN 7129) using Performer RPM 351 Cleveland 2V or 4V heads was still in development when we started planning our project. However, as of the '07 SEMA show, the intake is now available for those interested in building this type of engine with a carb.
We satisfied our needs by winning an original '69 Boss 302 intake manifold on eBay and seeking the assistance of the professionals at Wilson Manifolds. This type of project is right up Wilson's alley, and Gaby Labiosa and his team answered our call with a masterfully restructured OEM Boss intake for our engine's Edelbrock 351C 2V heads, as well as a new open-plenum, fuel-injected intake for our Air Flow Dynamics 4V heads, which is undeniably one of the most incredible intake manifolds we've ever worked with. Thanks to Cliff Moore of John Kaase Racing for his invaluable assistance with the effort.
One of the main pieces required for this type of puzzle (an 8.2-deck engine w/Cleveland-style heads) is an intake manifold. While pieces that facilitate using the heads down on a 9.5-deck Windsor short block are available, the Boss 302 market is pretty much nil, when it comes to aftermarket manifolds. We lucked out and scored an original, 1969 Boss 302 intake manifold on eBay, and immediately put it on a truck to Oakland Park, Florida, for Cast Manifold Dept Manager, Gaby Labiosa, and his team at Wilson Manifolds to give it an EFI makeover that's sure to make the classic-'Stang Melvins cringe.
The real-deal Boss was unmolested, save for some minor blending in the four-hole plenum area that had been done by the eBay seller. All of the ports were OEM clean and untouched.







The crew at Wilson Manifolds completely did away with the Boss intake's original four-hole setup and crafted this super-clean, true dual-plane plenum area. "We cut out the holes and lowered the bar in the center about 1.25 inches, mainly because the new Edelbrock heads require a lot of air velocity," says Gaby. "We gave it the biggest port job we could without cutting it in half." The plenum was also opened up to match the size of Wilson's tapered intake spacer.



The severe mismatch in port size between the Boss 302 manifold (big) and Edelbrock cylinder heads required many hours of welding, forming, and modifying. Gaby proudly shows off his team's handiwork: the result of completely reconstructing the 4V manifold to work with our 2V cylinder-head application.






While high air velocity is important for the Edelbrock heads, Gaby adds that there actually needs to be a "sweet-spot" for air speed in the plenum area of the modified Boss intake. To regulate the velocity, he added Wilson's 2-inch, tapered, lightweight spacer to increase the distance between the throttle body and plenum floor. By extending the plenum, air is slowed down enough so it can efficiently make turns to the runners.



Wilson's high-flow fuel rails and eight, TIG-welded injector bosses look absolutely insane on the new Boss 340 intake. The manifold setup is crowned with Wilson's 4150, billet throttle body; a carb-style (4-hole) unit that flows 1136 cfm, and looks sexy at the top of our radical intake.






The massive size of our Air Flow Dynamics 4V heads and their advertised flow (330 at 0.700-inch intake lift) made our need for an open-plenum intake critical. Here's a look at the centersection of the new Wilson Boss 302 EFI manifold we'll be using. Many thanks to Gaby and his crew for working with us to develop a new intake for our venture into unexplored territory for small-block Ford performance.




According to Gaby, the manifold's intake ports are all straight shots into the heads. With its perfect port-matching and maximum flow efficiency, Gaby feels the Boss 302 EFI intake will support as much as 700 flywheel horsepower without a problem.







Wilson's Boss 302 EFI intake manifold includes the same features found on our modified original intake (high-flow rails, stanchions, injector bosses, and so on). However, this new 8.2-deck intake for AFD SP4V cylinder heads uses a 1.5-inch tapered spacer over its mega-ported, open plenum.







Photo Gallery: Boss 340 Engine Build - Internal Components - 5.0 Mustang & Super Fords Magazine



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