We've chosen Hooker Super Comps for our dyno session. However, street torque doesn't come from huge 1-3/4-inch equal length primary tubes and a large 3-inch collector. It comes from smaller primaries and a smaller collector into 2-1/2-inch pipes. Header tube and pipe sizing boils down to what you want the engine to do in the car. Be conservative about pipe sizing and you will get torque. When pipes are too large, you lose torque but gain horsepower.
Torque comes of the raw mechanical advantage of stroke--that long lever you learned about in high school physics
We didn't have space to touch on this one last month, but block prep is key to durability. You will find a lot of FE blocks out there with what appear to be misdrilled main journal oil galleries. We're convinced this offset, or "misdrill," was intentional to control oil flow to main and cam journals. Jim Grubbs of JGM Performance Engineering believes FE blocks can use a little help, which is why he modifies the main journal oil galleries to improve oil flow to both mains and cams. Jim also distresses castings to minimize the risk of cracks at casting parting lines where he grinds these surfaces smooth.
Main saddle oil galleries...
Main saddle oil galleries are opened up to improve oil distribution to both main and cam journals. Notice the good crosshatch pattern here for good bearing security and crush.
Ragged edges, known as stress...
Ragged edges, known as stress risers, are ground smooth to prevent cracks.
The difference between building a Mustang stocker and a restomod is fitment and compatibility of aftermarket performance parts. For example, our good-looking Ford Racing "Cobra LeMans" cast valve covers wouldn't clear the Comp Cams shaft-mounted rocker arm assemblies without minor internal grinding at each end of the valve covers in order to clear the end supports.
Mark learned something about...
Mark learned something about compatibility and fitment when it was time to install our Ford Racing Cobra Le Mans pent roof valve covers. They didn't clear the Comp Cams rocker shaft end towers.
Using a die grinder, Mark...
Using a die grinder, Mark clearanced the ends of each valve cover, which made for a perfect fit.
Every engine testing experience is unique. This is only the beginning of dyno testing Trans Am Racing's 442ci FE big-block. First, we want to know what this engine will do right off the engine stand. Then we want to conduct a series of tests with both Edelbrock dual-plane and single-plane manifolds to see what happens to this engine's powerband. Because dual-plane manifolds have long intake runners for better low to mid-range torque, you can expect torque to come on strong around 2,500 rpm and pass the baton to horsepower around 5,800 rpm.
The single-plane manifold with its straight shot into the intake ports means horsepower on the high end and a loss in low to mid-range torque. Long intake runners deliver torque because they afford velocity through those runners as low to mid-range rpms.
In the months ahead, we're also going to test this 442ci FE stroker with Holley's new EFI throttle body injection system to see what can be expected from both carburetion and electronic fuel injection. We're also going to try different sized carburetor and jet swaps to see where power can be gained via small changes.
The numbers here demonstrate what you can do with a 390 FE block when you fill it full of displacement and mechanical advantage. By adding stroke and a pinch of bore to the grocery-getter 390 along with ported Edelbrock Performer RPM heads and induction, plus Comp Cams roller tappet technology, we wind up with 582 horsepower and 557 lb-ft of torque--both between 5,000 and 6,000 rpm.
| RPM | HP | TQ |
| 2,500 | 179 | 376 |
| 3,000 | 277 | 485 |
| 3,500 | 347 | 520 |
| 4,000 | 407 | 534 |
| 4,500 | 472 | 550 |
| 5,000 | 580 | 557 |
| 5,500 | 572 | 546 |
| 6,000 | 582 | 510 |
| 6,300 | 576 | 480 |
10 Remember, as displacement...
10 Remember, as displacement increases, so does fuel demand. Because our 390 is no longer a 390, we must consider fuel consumption and the need for greater gph (gallons per hour) at wide open throttle from our Holley 110-gph pump. If your Mustang has a 5/16-inch fuel line, it is not large enough for an FE. This 442ci FE needs at least a 3/8-inch line from the tank to the fuel pump and the fuel pump to the carburetor.
11 Mark suggests following...
11 Mark suggests following the plenum design when selecting a carburetor base gasket. If it's a four-holer, choose accordingly. For our open plenum, we wanted the thickest gasket possible to help insulate the carburetor from manifold heat.
12 This is Holley's new Ultra...
12 This is Holley's new Ultra HP 950-cfm carburetor, which may seem like a lot of carburetor, but remember this isn't a 390 anymore. Displacement is 442ci along with an aggressive hydraulic roller cam, induction, and heads. Dyno time will begin with generous jetting to play it safe, then go leaner with each pull until power falls off.
13 Dyno testing begins with...
13 Dyno testing begins with 92 jets in the primaries to begin rich and gradually go leaner to prevent the risk of engine damage. Start with conservative timing and begin your pull with rich jetting on both sides. We suggest a plug reading first, which comes after a wide-open throttle pull under load at 4,500rpm, then a shutdown. Adjust the jetting to the plug reading.
14 There's a lot of chatter...
14 There's a lot of chatter about carburetor spacers, but here's the deal. Carburetor spacers are good for increasing torque, not horsepower. Choose a carb spacer based on manifold plenum design. Open plenums get an open plenum spacer. Four-holers get a four-holer. You want a smooth transition from throttle bores to manifold plenum.
15 Unless you're building...
15 Unless you're building a stone stocker, opt for ARP fasteners torqued to specifications. Also, never reuse fasteners like cylinder head and main bearing cap bolts. Always use new ones.