In the last few issues of MM&FF, we've been modifying an '85 5.0L Mercury Capri with bolt-on parts from Summit Racing Equipment, Performance Distributors, Holley, Weiand, Dynomax and Weld Racing. The modifications have allowed us to take this once-sluggish 15.6-second ride to a mercurial 13.31 at 102 mph. This month, we aim to improve on this accomplishment with the addition of high-performance cylinder heads and a hot camshaft.
We've never bothered to dyno-test our Capri simply because we're having too much fun at the dragstrip with it. Not everyone can afford dyno time either, and it's much more reasonable to pay $20 at the local test-and-tune to see if your modifications have made a change for the better, not to mention that cars are meant to be driven and we'd rather talk about an adventure to the track.
To recap the present state of our mighty Mercury, we started with a mostly stock 5.0L Capri, its only modifications being an Edelbrock 750-cfm carburetor, 3.73 gears, and a pair of Flowmaster mufflers. We spent the first track session learning what the car responded best to with regard to shift and launch rpm. We then added lightweight Weld Draglite wheels and Toyo Proxes 26x9-inch slicks and skinnies, and we bumped the timing. With these changes, we whittled the quarter-mile time down from a 15.44 to a 14.26, picking up about 5 mph in the process.
We followed up with a Holley 600-cfm carburetor and Weiand intake manifold combination from Summit Racing Equipment, as well as an exhaust system from Summit and Dynomax. Performance Distributors also sent us its Firepower ignition system to give the old lump a healthy tuneup. These enhancements allowed us to chop at the clocks some more, which put the Capri's best lap at 13.55 at 99 mph. We did make a "hero run" with the serpentine belt removed and went 13.31, but we couldn't hot lap it in that trim. The 13.55 is a more accurate representation of what it can do. The 13.31, however, does hint that there is more power to unlock from the 5.0L, and we'll address that next month.
We had a leaky freeze plug and some very brown coolant that told us we needed to change al
This month, though, we promised to bolt on a set of high-performance cylinder heads and a hot camshaft, and we did just that. We went to Tri State Cylinder Head and ordered a pair of its Flo Tek 5.0X aluminum cylinder heads designed for pedestal-mount rocker arms. The 5.0X heads feature 180cc intake runners, 1.94-inch intake/1.54-inch exhaust valves, 58cc combustion chambers, and valvesprings good for cams with 0.550-inch lift. They also feature hardened locks and retainers, manganese/bronze valveguides, and phosphor/bronze exhaust guides, as well as a five-angle valve job.
You can get the 5.0X heads in a stud-and-guideplate version, but in either case, the retail price is the same-a smoking $798 for the pair. That kind of savings leaves you cash for other speed parts, like the Ford Racing Performance Parts 1.6:1 aluminum roller rocker arms (PN M-6564-BS51) and Trick Flow Specialties 6.25-inch hardened pushrods (PN 21406250), which are a 5/16-inch-diameter rod made from 4130 chromoly. During the installation, we realized that we needed to shim the rocker arms to obtain the correct lifter preload, and we used the 0.060-inch shims from Ford Racing Performance Parts' shim kit (PN M-6529-A302).
At just $800 for the pair, Flo Tek's 5.0X aluminum cylinder heads are a sweet bargain, and
For our camshaft selection, we had a myriad of choices, even with the limitation of the stock piston valve reliefs. When it came down to ordering one, we went with a Ford Racing Performance Parts B303 camshaft. The venerable M-6250-B303 camshaft offers 224 degrees of duration at 0.050 on both the intake and exhaust (284/284 advertised), and 0.480-inch of valve lift. It's a great cam for the average street car as it offers a great burbling idle sound and an increased rev range to 6,000 rpm. Best of all, it's just $195 through Summit Racing Equipment, which provided us with the cam, rocker arms, and the pushrods for this buildup.
Available in either pedestal- or stud-mount form, the 5.0X heads feature a 180cc intake ru
The Flo Tek heads offer a 1.94 intake valve and a 1.56 exhaust valve.
For our valvetrain choices, we turned to Summit Racing Equipment. Summit set us up with a
After replacing all of the freeze plugs in the engine, giving it a fresh paint job, and cl
Xenos then installed the factory cam retaining plate, followed by the timing chain that Su
The timing cover was next. We really like Cometic's timing cover gasket, as it is a thick