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Carbureted Mercury Capri Buildup - 4 Barrels Of 5.0L Fun
MM&FF Takes It Old School With A Carbureted Mercury Capri Build Series.
The Fox chassis Mustang that made its debut in 1979 was a sign of good things to come. Ford made considerable advancements each year, and by 1985, Ford had the Mustang rocking out with a 210hp 5.0L engine-it was the most horsepower from a late-model Mustang until that point. In addition to a new hydraulic roller camshaft, the 5.0L also received new tubular steel exhaust headers and a high-flow Motorcraft/Holley 600-cfm carburetor. This would be the swan song for the carbureted Mustang, however, as in 1986, Ford pulled the four-barrel for sequential multi-port fuel injection.
The carbureted Fox-body cars are getting harder and harder to come by, and it seems like most have been ridden hard and put away wet. It's hard to come across any that are close to stock, but we just happened to snag an '85 Mercury Capri that's about as close to stock as one will find without buying a rare, low-mileage example.
According to website www.ascmclaren coupe.com's factory Mercury literature, the Capri in question is an '85 GS model, equipped with the 5.0L engine and the T-5 five-speed manual transmission. The interior is fairly clean, though it looks as though a hungry dog may have gnawed at the passenger-side headrest. On the outside, the panels of the 134,000-mile car are in decent shape, but one of the previous owners attempted to paint the car and while they nailed the basecoat, the clearcoat mix wasn't quite spot-on and now looks like a week-old sunburn. What we were most pleased with was that the front bumper cover was in relatively pristine condition. Oftentimes these are broken, bashed, cut, and scuffed because of their low-slung nature.
On the testdrive, we were informed that the car had no brakes, other than the emergency brake, but it ran well, was reasonably quick and idled smoothly. It was also relatively stock, with little modifications. The person we bought the car from said he had 3.73 gears installed in the 7.5 rear axle, and at some point, another owner ditched the factory Holley carb and Ford air cleaner for an Edelbrock 750-cfm carburetor and open element air cleaner. The factory headers, Y-pipe, and dual exhaust were all still there, as were the 10-hole 15-inch wheels with Mercury-spec center caps. We made the deal and walked away with the car for $1,300. We probably should have bargained the price down further on account of the master cylinder being filled with a soupy paste along the lines of grit-infused hand cleaner, but we were stoked enough about the rest of the car that we felt good about the purchase price.
After getting the Capri back home and giving it the once over, we decided that getting the brakes working was priority. We could have rebuilt the factory setup, but since we're going to be adding more horsepower to the car, and running it at the dragstrip, we opted for an upgrade from MPS Auto Salvage. MPS set us up with a complete '87-newer front brake system, which included the calipers, freshly turned rotors, spindles, brake lines and master cylinder.
We ended up replacing the rear wheel cylinders as they were leaking, and to be sure to get all of the sediment out of the system, we flushed it. We had a pair of old Flowmaster mufflers lying around, so we tossed those on as well.
We gave the Capri a thorough cleaning inside and out, and took it for a few testdrives to deem it track-worthy. All was good, so we loaded up the rare Fox-body and headed to our local track.
With just the Edelbrock carb and the mufflers, our two get acquainted passes came in at 15.44 seconds at 89.79 mph (2.30 60-foot time) and a 15.68 at 89.45 (2.44 60-foot). Not bad, but there was definitely room for improvement. We advanced the timing two degrees, and the Capri responded with 15.29 at 88.62 mph (2.38 60-foot).
Feeling that the car was falling off, we started short-shifting the car at 4,700 rpm instead of the 5,000 where we had been shifting. With that, elapsed time didn't change much, but the speed did, as we clocked a 15.29 at 91.65 mph (2.31 60-foot) and a 15.22 at 91.75 mph (2.37 60-foot). We dialed in two more degrees of advance for the next run, but the slight improvement in the 60-foot time (2.22 seconds) netted a better 15.10 pass at 91.55 mph.
For the next few runs, we concentrated on the launch and 60-foot time, as we believed we could improve on this. Our beliefs proved correct, as a 2.17-second short time netted a 14.86 at 92.17 mph. A 14.97 run at 92.09 mph (2.23 60-foot) followed, as did a 14.89 at 92.37, which came by way of another 2.17-second 60-foot time.
Our Capri pilot for the project, George Xenos, got a little more aggressive on the launch and popped the clutch at 3,500 rpm. This dropped the 60-foot time to 1.92 seconds, which was followed by a 14.46 at 92.91 mph. The added traction combined with a lighter wheel/tire package definitely improved the elapsed times. Unfortunately, our night came to a close on the next pass, when a 4,400-rpm launch produced a loud bang, and the Capri crept to a halt. Upon further inspection, we had sheared several teeth off of the spider gears in the differential.
Following our track excursion, we had to remedy the rear axle issue. To do that, we called MPS Auto Salvage in Statham, Georgia. MPS sent us a complete rear axle assembly and we then called up super parts house Summit Racing and ordered some beefy internal components for it. While you can spend thousands on building a rear axle, we opted to cut costs by going with the Moser 28-spline forged steel axle shafts and keeping the stock differential. Then we ordered a 3.73:1 ring and pinion to match what we had in the 7.5 rear. Summit also provided a Richmond installation kit as well.
With that out of the way, we set our sights on the next track day, which came two weeks later at Gainesville Raceway in Gainesville, Florida. To keep things consistent, we stayed with a 3,000-rpm launch, and shifted at 4,700 rpm, as that's what the car seemed to like best. With that technique, our first run came in at a 14.42/94.35 mph with a 2.08-second short time. We backed that up with a 14.43/93.24 run (1.99 60-foot), and then pulled the very dirty air filter and left the lid off. The better result came from the quicker 1.93-second 60-foot time-at the stripe, it was a 14.26 at 94.10 mph.
As purchased, the Mercury Capri delivered a 15.44-second at 89.79-mph performance, and we've managed to whittle that down to a 14.26 at 94.10 mph. A second improvement in elapsed time and an increase of nearly 5 miles per hour isn't bad progress at all, but we have more in store for the Capri. Next month, we'll have an ignition system makeover, as well as a carburetor/intake manifold setup to try out. After that, we're going to add some cylinder heads and a hotter camshaft and see where it goes from there.