Last month, we showed you how to take a sedate 390 FE big-block and give it stroke, which ultimately translates into torque and more than its share of horsepower when it's time to pin the butterflies. This time, we want to get into the more finite details on how to build common sense street power into a 390 High Performance V-8. Too many of us get caught up in that dreamy eyed horsepower thing without considering first how our engine will be used.
"Horsepower" is an oft-misused term coined by Madison Avenue advertising agencies because it sells automobiles. It also helps the aftermarket sell engines and performance parts. However, horsepower is a meaningless dynamic unless you are going racing. Even then, it's rather meaningless because horsepower is used only at high rpm and for a short time at wide-open throttle. What matters most is torque--the grunt factor that gets us going before it hands all the fame and glory off to horsepower. We infuse stroke into an engine to make more torque, not horsepower. Torque comes of the raw mechanical advantage of stroke--that long lever you learned about in high school physics. With a lever, you can move the world. The more stroke and connecting rod length (rod ratio) we can give an engine, the more torque we're going to make. And that is what this 442ci FE is all about.
"This 442ci stroker demonstrates how well this combination of parts works together," explains Trans Am Racing's Mark Jeffrey. "When you run the air hat on a dyno, it monitors how much air is being drawn into the engine. The dyno's programming calculates how much power is made. When the percentage of in and out have a huge differential, you know by the VE numbers that you made a poor decision with parts selection. It means your parts aren't working in harmony. To get torque, you need bore, stroke, and the right valve timing events as they relate to piston travel. Although this seems simple in theory, it isn't in reality because there are so many hurdles. You've got to be a great engine architect in order to outfit your FE with the right combination of parts and chase it with proper tuning.
1 Check out this shaft-mounted...
1 Check out this shaft-mounted roller rocker set up from Comp Cams. Made from 7000 series billet aluminum, these rockers are needle bearing supported and fully adjustable. They keep valvetrain geometry constant and predictable.
2 Installed, the Comp Cams...
2 Installed, the Comp Cams shaft-mount roller rocker setup looks terrific and provides reduced friction and greater rocker ratio. Mark spent a lot of time blueprinting this valvetrain to get the rocker to valve stem tip relationship just right. We didn't have pushrods when this image was taken.
3 Milodon's windage tray...
3 Milodon's windage tray and oil pan are a near perfect fit. Mark had to do some clearancing around the oil pump and crankshaft counterweights, which is routine whenever you add stroke or stud the main journals.
Mark has an instinct for cam and head selection and isn't afraid to push an engine to its limits. In the heart of this 442ci FE stroker is an aggressive, yet streetable, Comp Cams hydraulic roller camshaft, which unleashes power not only from its profile but also from reduced internal friction. It gets better with Comp Cams' new shaft-mounted rocker arm assembly for FE big-blocks with Low-Riser cylinder heads, including the Edelbrock Performer RPM castings that Mark has fitted to this FE. These 1.76:1 ratio, 1.200-inch wide billet rocker arms pivot on precision needle bearings where nothing can disturb their geometry. What's more, they're fully adjustable. End stand kits are purchased separately.
Mustangs Plus set us up with a Milodon oil pan, windage tray, and pick-up for our Trans Am Racing 390/442. Mark needed to do some clearancing in order to clear the crankshaft counterweights and oil pump. The windage tray keeps oil out of the spinning crank and rod journals, which prevents foaming at high rpm. Even if you're building a stock 390 FE, a windage tray is still a good idea for those wide-open throttle experiences. Oil windage also consumes power because it creates internal resistance when oil wraps itself around the crankshaft and connecting rods at high rpm.
When you build an engine, plan an exhaust system to match. Tuning an exhaust system is as tricky as choosing a cam, selecting heads, and deciding on a manifold and carburetor. Your Mustang's exhaust system begins at the header flange and ends at the tailpipes. Every decision you make in between determines rear wheel power.
4 Because we're going to...
4 Because we're going to the dyno with a 442ci FE stroker, we've asked Hooker for the largest header size possible--the Super Comp #6114-1HKR with 1.750-inch primaries and 3-inch secondaries and collectors.
5 We've opted to use a high-flow...
5 We've opted to use a high-flow Edelbrock water pump to compliment the Performer RPM heads and induction. The Edelbrock pump is lighter, providing more aggressive coolant flow and heat dissipation.
6 We like the Professional...
6 We like the Professional Products harmonic balancer for outstanding quality and timing marks you can see in just about any light. Always check harmonic balancer indexing because all balancers aren't properly indexed. We've seen harmonic balancers as far off as 11-degrees, which can be destructive if you crank in too much timing. When you fire your engine, go for no more than 36-38 degrees total timing at 3,000 rpm with vacuum advance connected.
7 Pin point precision ignition...
7 Pin point precision ignition performance comes from MSD's billet distributor with vacuum advance for street use. For initial fire-up, Mark opts for 6-12 degrees BTDC (vacuum advance disconnected and plugged) and runs the engine at 2,500 rpm for 30 minutes for proper break-in and ring seating. Proper break-in should include loading the engine and applying throttle. This is where dyno testing is a good investment in a new engine. Average cost is $600 to $1,000 per session.
8 Ignition wire routing is...
8 Ignition wire routing is crucial to performance. We don't want crossfire or a short to ground even with the best ignition wires. Be attentive to how your ignition wires are routed. We're using Made 4 You ignition wire holders, which are outstanding pieces that look good and last a long time.
9 Here's how to tune the...
9 Here's how to tune the vacuum advance rate on distributors so equipped. An Allen wrench turns the advance rate adjustment inside, which works the same way as a factory Autolite vacuum advance. The more spring pressure you apply with either shims or this adjustment (clockwise), the slower the rate of advance. Take away shims or back off on the adjustment (counterclockwise) to reduce spring pressure, the faster the advance rate.
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.