The Big Wedge - Mopar Big-Block Engine
Built from scratch in just 10 days, this 506-inch Mopar makes 730 horsepower on pump gas with mostly off-the-shelf parts.
From the February, 2009 issue of Popular Hot Rodding
By Steve Dulcich
Photography by Johnny Hunkins
Mopar's big-block "wedge" engine certainly never enjoyed the spotlight that surrounds its close cousin, the Hemi. The wedge may not have the glamour factor of those broad valve covers, but it delivered the kind of power that fueled the mystique of the performance car era. Introduced in 1958, the Chrysler wedge certainly had some big shoes to fill, as the famed 392 Hemi was in its last year as Chrysler's premier engine. That's Chrysler--a company that built its reputation on engineering, and high-output, bulletproof powerplants. In the large Chrysler 300, the new wedge didn't disappoint, but the then-new engine series really caught the limelight in 1962 when the Max Wedge came on the scene.
Built for unrepentant power, the Max needed no excuses and went on to sweep the floor for the next three years in sanctioned competition. The wedge worked, but in a twist of irony, the Hemi re-appeared in 1964, forever usurping the reputation as top-dog of the Chrysler camp. The 426 Hemi bore no resemblance to the earlier Hemi mill, but in fact was primarily a top-end modification of the basic Wedge big-block design.
The Chrysler wedge was built in two different basic configurations, each with a distinct deck height. The "low-deck" B-wedge featured a deck height specification of 9.98 inches, and carried a 3.375-inch stroke. OEM displacement variations began at 350 cid at the inception, and expanded to 361, 383, and 400 cid, determined by bore size. The 10.725-inch tall "raised-deck" RB wedge carried a longer 3.750-inch stroke and was available in 383, 413, 426, and 440-cube displacements, again by virtue of differences in bore diameter. While the Hemi basked in the fame of its racing success, the wedge went on to rule the streets, at least by virtue of sheer numbers. When the musclecar era was in full swing in the period from 1967-71, Chrysler was in the thick of it with legendary cars like the Charger, the GTX and Roadrunner, R/Ts and SuperBees, Challengers and 'Cudas, not to mention the big-block A-body Formula S and GTS. Here, in the midst of muscledom, the 383 and 440 wedge were everywhere, while the limited-production Hemi was a rare sight indeed. Would there even have been a "musclecar era" as we remember it without the ubiquitous Mopar wedge?
Mopar big-block wedge production ceased in 1978, and that could well have been the end of the story, but for the sheer devotion of Mopar musclecar enthusiasts. Interest in these old cars, and the engines that powered them, just never seems to diminish. As a result, parts development for the wedge engine has never slowed. To the contrary, really, there is more support, speed equipment, and ongoing R&D in the world of wedge power today than there ever was--far more. In what may play out to be another ironic twist in the evolution of the wedge, it can be argued that with the current state of parts development, the wedge design has more power potential than the Hemi that stole the limelight all those decades ago.
T&B Performance, of Monroe, Wis., thought so. The wedge featured here was built to compete in Popular Hot Rodding's annual engine building competition, the Engine Masters Challenge. It was the only Mopar at the event, and interestingly, the only Mopar happened to be a wedge, not a Hemi. Surprised? If previous experience is anything to go by, the wedge seems to carry an advantage. In fact, in the 2003 event, a Mopar wedge set the highest peak power level in the competition. [That engine, in fact, was built and fielded by the author, Steve Dulcich. -ed.] Super-high output wedge combinations wouldn't be conceivable without the continual refinement of aftermarket power parts, but there is a great deal of validity in the original design. In fact, the T&B wedge is deeply rooted in the original factory platform. Actually, its foundation is a factory 383 Mopar block cast in the year when the Plymouth's Road Runner first laid tire to the tarmac, in 1968.
Prepped with a 0.040-inch overbore, the factory block is stuffed with a 4.375-inch stroke crankshaft. The result is a 1.00-inch stroke increase that would have been unimaginable to the factory engineers all those decades ago. The stroker crank adds 123 cubes to the low-deck wedge, far eclipsing the cubic capacity of the largest of Mopar's factory wedge offerings. The block was fortified with a short fill of Hard Block, adding some additional rigidity to the bottom-end while helping to buttress the cylinder walls. The bottom-end arrangement is all stock Mopar, including the main caps, although reinforcement was added in the form of a main girdle from Chenoweth Racing. Brenda Foley of T&B commented, "The nice thing about the Chenoweth girdle is that there wasn't any external machine work involved in putting it on. It's just a matter of mic-ing it, and setting your heights properly. For someone who doesn't have the machines to mill off the tops of their maincaps, I think it would be a good add-on."
These long-armed crankshafts for the wedge are not an unusual novelty, but are readily available as off-the-shelf pieces from a variety of suppliers. This one is from Eagle Specialty Products, and is just one of several stroke lengths stocked by Eagle. Aftermarket cranks for Mopar wedge engines are commonly available in a choice of the factory 2.375-inch rod journal diameter, or with the 2.200-inch dimension of a factory big-block Chevrolet. The Chevy journal carries a three-fold advantage, reducing bearing speed and friction, while providing increased crankcase clearance, and allowing a much broader range of choice in aftermarket rods. The rods used in this engine are also readily available, a set of H-beam Eagle units in a 6.700-inch length.
The rods and crank received minimal prep; the crank counterweights were mildly profiled, and a Teflon-based oil-shedding coating was used on both the crank and rods. Brenda Foley explained the concept: "The oil-shedding coating is kind of like wax on a car. Instead of the oil really sticking to the crankshaft, it just allows it to shed more easily; we were trying to keep the windage down as much as possible since we did not have the wide kick-out pans the Chevys do." Further helping to reduce windage is the re-directed drainback achieved through modification in the lifter valley, Brenda continued, "We were trying to keep as much oil off the crankshaft as possible, to keep the windage at the minimum. It doesn't have much room to go when it is stuffed between the crank and the block."
Up front, we find a Jesel...
Up front, we find a Jesel belt-drive system--the ideal apparatus to quickly and easily determine the most advantageous phasing position for the COMP Cams roller camshaft behind it. A TCI Rattler damper looks good at the front of the crank.
With over 500 cubes worth...
With over 500 cubes worth of air to dispense, T&B went straight to a King Demon RS carb. The removable sleeves forming the venturis allow the capacity, and, more importantly, the air velocity to be readily altered in the search for power.
Beneath the behemoth Demon...
Beneath the behemoth Demon rests an HVH "Super Sucker" carb spacer. It's there for a reason. T&B told PHR: "We tried with and without the HVH spacer, and we did pick up."
A glimpse inside the plenum...
A glimpse inside the plenum of the B1 intake manifold reveals extensive modifications. Note the epoxy filling of the floor, the porting, and the runner extensions welded and blended from the runner branches. Why are they there? According to Brenda, who performed the work: "The runner extension was one of the things we looked at and thought maybe we can get a little better signal to the carburetor--that sort of thing, with those extensions in there."
Porting and epoxy work also...
Porting and epoxy work also characterize the intake manifold port runners. The fill measured approximately 3/8 inch on the floor at the manifold's juncture to the cylinder head.
Epoxy work is also employed...
Epoxy work is also employed in the lifter valley, this time to curb the factory oil drainback system in favor of a more controlled approach. Inside, the intake ports have a deck of epoxy forming the intake port floor, matching the work done to the intake manifold.
If you take the shorter of the two Mopar wedge variants, add substantially to the stroke, and then employ connecting rods measuring 0.342-inch longer than stock, you'll come to appreciate the spacious real estate Chrysler employed with these engines. Bear in mind that strokes over 4.150 inch create a nervous proximity with the factory internal oil pump pick-up, particularly at the factory crankpin diameter. For longer strokes, as used with this wedge, an external pick-up, such as the Milodon set-up used here, is the usual course of action. The piston compression height is dramatically altered with such a combination. Factory Mopar wedge pistons typically carried a compression height hovering in the vicinity of two inches. With this combination of stroke and rod length, the required compression height is reduced to a fraction over one inch. (1.092 inch to be exact.) The resultant loss in mass is dramatic, as is the reduction in reciprocating friction.
T&B took a novel approach with the piston for this engine, looking for minimal friction with the custom JE forged pieces. The piston employs a two-ring package, carrying a 1.2mm Total Seal gapless top ring, no second compression ring, and a 3mm oil ring assembly. We asked about the oil control with the two-ring setup, and Brenda informed us: "Actually everything looked really clean; it looked good in that way. On our oil ring we didn't go with the absolute lightest and went with just a little more tension." We suspect the piston and ring combination contributed to this engine's healthy output. The compression ratio was 12:1, and interestingly, we noted that there was no audible detonation with 91 octane pump gas while the engine worked the dyno. Brenda told us: "We ended up at 12:1, but we started off at 11.5 and had no detonation, so we bumped it up another half point. In the competition, we really didn't have any detonation like a lot of the other competitors. I think because we had a very tight quench clearance, and I think with the smaller chamber and the piston configuration, we had a very effective burn."
Back in the '60s, the Chrysler wedge heads had enough flow to breathe life into torquey 383- and 440-cube street engines. To be competitive in today's world, high-flowing cylinder heads are a must. Brodix B1 heads are just the ticket for supplying 506 cubes of raucous Mopar. These heads were modified by T&B, and fitted with Ferrea valves measuring a healthy 2.300 inch on the intake, and 1.72-inch on the exhaust. The valve size bias clearly favors the intake, and is part of the strategy to letting an in-line wedge head breath. Brenda did the port work, which involved epoxy filling of the floor in both the heads and the matching Brodix B1 intake manifold. However, given more time to prepare the engine, some changes might have been made. Brenda disclosed: "We did put too much filler in, looking back at it. We'd like to go less than that and see what it would do. I think we just went a little too far, and with about half that much in it, it probably would have given us a little bit better area. We matched the intake manifold and heads in that way."
A COMP Cams solid roller directs the valve operation, and does so with the authority of an immodest 261/265-degree duration spec at 0.050-inch tappet rise, and 0.735-inch lift. The idea is to really open the window for airflow into the engine. The relatively tight lobe separation angle and shallow installed centerline are aimed at bringing impressive torque to the arena by the intended peak operating speed of 6,500 rpm. Manley springs, retainers, Smith Brothers pushrods, and Brodix 1.7:1-ratio rockers work in concert to deliver the motion to the valves as the cam lobes intend.
We were fortunate to see the T&B Mopar in action at the Engine Masters Challenge event at World Product's Long Island, N.Y. facility, and even more so to meet the people behind the engine. T&B Performance Machine is a family business, and that was demonstrated when Tom, Brenda, Grandma, and all the kids came to enjoy the week's events and the thrills of competition. The engine was competitive, and one of the cleanest running of all the entrants under the constraints of trying to maximize power within the 91 octane pump gas rule. Competing allows this team of builders to experiment in a way that would otherwise seem impractical. As Brenda told us, "One of the real fun things about the Engine Masters Competition is that we get to try things that we wouldn't usually get a chance to on a customer's engine. Engine Masters gives us a good opportunity to try different things, and see if they are beneficial to encourage our customers to do as well." We look forward to seeing what they bring this year.
The B1 top-end package helped...
The B1 top-end package helped revolutionize Mopar wedge power production. The high flow upstairs was just the prescription to make those cube lurking below really come to life. You won't see this kind of power with your old factory iron 906 castings.
Exhaust out is as important...
Exhaust out is as important to the flow system as air in. T&B looked to the Mopar experts at Tube Technologies in Corona, Calif., for a set of their proven 2-to-2.125-inch step headers. Note the EGT fittings, used for testing the combination. "The EGTs let us check the exhaust temperature to make sure we didn't have a cylinder that was too far off the others, and just making sure everything is consistent. Although you have your air/fuel ratio on the dyno, it's nice to have them as a backup check."
A reverse-flow cooling system...
A reverse-flow cooling system from Indy Cylinder Heads directs coolant into the heads first, and pulls the warm water back out the block. Brenda at T&B explained the concept: "Of course you are trying to keep heat out of the cylinder heads, and that sort of thing. Another positive thing on a side note is that it requires the use of a small-block Chevy water pump, and we already had one."
Note the heavy offset in the...
Note the heavy offset in the big Mopar's intake rockers. The factory shaft-mounted rocker system makes it possible. Offsetting moves the intake pushrod outboard of the port, eliminating one of the key constrictions in an inline-valve engine--the pushrod pinch point of the port.
Examining the B1 intake port...
Examining the B1 intake port clearly illustrates the advantage of the offset rockers--namely unimpeded cross sectional area throughout. These ports can be so large that they can be filled at the floor, improving the port shape, while still maintaining sufficient port area to meet engine demand.
Comprising the hardware to...
Comprising the hardware to fill out the cylinder head castings, T&B utilized generously sized 2.300-inch Ferrea intake valves, and modestly sized 1.72-inch exhaust valves. The spring/titanium retainer/lock package is from Manley, while the pushrods are a custom set from Smith Brothers. The rockers are a Brodix item, designed specifically for the B1 heads, and have a ratio of 1.7:1.
A defining characteristic...
A defining characteristic of the B1 heads is the modified heart-shaped chambers, and angled spark plug location. T&B is very aggressive with the quench clearance, pegging the spec at an edgy 0.025 inch. With the way the chamber was scrubbed at the quench side, we'd say that's cutting it to the bone.
Taking the piston and rod...
Taking the piston and rod combination into consideration, we have a mixture of the very commonplace, and the unusual. The rod is an Eagle H-beam, known for its reliability, with a Chevy journal diameter of 2.200 inch, and a 0.990-inch Chevy pin. The piston exhibits a shallow reverse dome, while both the piston and rods take advantage of engine coatings.
"Unusual" comes into play...
"Unusual" comes into play in the piston design. The piston has an exceptionally short compression height of 1.092 inch, and carries only two rings. A 1.2mm compression ring is backed only with a 3mm oil ring assembly. Lateral gas ports improve the compression seal.
Pulling the pants off the...
Pulling the pants off the Mopar wedge shows the details of a Milodon louvered windage tray. The large external pick-up Milodon pan keeps oil stocked well below the spinning crank.
Meet the T&B team(left to...
Meet the T&B team(left to right): Tom, Brenda, Grandma Joyce, Leeza, Lez'lee, McKenzy, and Dempzy.
Inside the crankcase is a...
Inside the crankcase is a Mopar big-block bottom-end, just the way Chrysler built it. Even the main caps are factory, however, reinforcement is provided by a stud girdle and fastener kit from Chenoweth Racing.
|Dyno Results |
|506-cid MOPAR WEDGE |
|Engine Specifications |
|Bore:||4.290 inch |
|Stroke:||4.375 inch |
|CID:||506 cubic inches |
|Compression ratio:||12:1 |
|Camshaft:||COMP, solid roller |
|Cam duration:||261/265 degrees at 0.050-inch tappet rise |
|Cam lobe lift:||.432/0.432 inch |
|Rocker ratio:||.7:1 |
|Lobe separation:||108 degrees |
|Installed centerline:||102 degrees |
|Top ring:||Total Seal gapless, 1.2mm |
|Top ring gap:||0.028 inch |
|Second ring:||none |
|Second ring gap:||none |
|Oil ring:||3mm |
|Piston:||JE reverse dome, 0.990-inch pin |
|Gas ports:||lateral gas ports |
|Quench clearance:||0.025 inch |
|Block:||Chrysler 383, 1968 |
|Crankshaft:||Eagle, forged |
|Rods:||Eagle, 6.700 inch |
|Main journal:||standard Mopar, 2.625 inch |
|Main bearing clearance:||0.002 inch |
|Rod journal:||2.200 inch |
|Rod bearing clearance:||0.002 inch |
|Cam journal:||standard Mopar |
|Bearings:||Calico coated |
|Cylinder head:||Brodix B1, ported |
|Intake valve diameter:||2.300 inch |
|Exhaust valve diameter:||1.720 inch |
|Intake manifold:||Brodix, ported |
|Carburetor:||King Demon RS, black venturii |
|Headers:||TTI 2-to-2.125-inch step |
Building this engine for a competition is a pressure cooker of an endeavor, and the really remarkable thing about this effort is that it was put together in only 10 days. That took some real hustle from the suppliers, and a near around-the-clock effort on the part of Tom and Brenda Foley of T&B. In the process, there were individuals who went way beyond the call of duty in getting the job done and lending to the success of this entry. We wanted to acknowledge them here:
Green Bay, WI
Rock City, Il
Performance Parts Distributor
Lone Automotive Motorsports
Supplied by Kilpatrick Transmissions
German Valley Machine
German Valley, IL