PART II - CAM AND CARBURETION CHANGE (PLUS A FEW OTHER TRICKS) BRING THE SIX CYLINDER INTO THE MID 80'S AND LOW 16'S
The relative straightforward and inexpensive modifications up to this point added 35 horsepower to the Mustang six banger. Ak got still another 25 horsepower with additional modifications, some of which were not so common.
At this juncture, Ak decided that because, the engine responded so well to minor changes, he would dig a little farther and see what he could come up with in the way of more performance.
"Automatically, our first thoughts were of the camshaft," says Ak, "which in the case of the stock unit is designed strictly for maximum torque and economy. In this area, it just can't be beat. However, the horsepower range comes to a screaming halt at 4000 rpm. And since we were desirous, of going on up to 5500 rpm, we installed a special grind. We didn't wish to destroy the inherent smoothness and tractability of the little six or lose the silent hydraulic valve train action. So the specs of our cam were 260° duration, 0.408" lift, 42° overlap, intake opens at 21° BTDC. By comparison, the stock cam has 256° duration. 0.368" lift and 28° overlap."
More Spring Pressure
After changing the cam, Ak had to add a little more spring pressure for the added rpm. He used the valve retainers from a 1962, 260 Ford (part number C2OZ-6514-A, 14¢ each). He also used the standard springs from a 289 Ford (part number B6A-6513-A, 45¢ each).
Spring pressure worked out at 90 pounds (valve closed) and 190 pounds open. Installing the cam and springs added 5 horsepower. This made it possible to rev the little six up to 5500 rpm with no hydraulic pump-up. At the same time Ak put the cam in, he also installed pushrods (part number C0DE-6565-B) and adjustable rockers (part number CODZ--6564-A), from earlier Falcon engines. They are the same ratio, but give a handy method of adjusting pushrod lengths when changing cams. Ak definitely recommends this change.
Dual Distributor Point Springs
During The test on the cam, Ak noticed that the ignition (in its stock form) was rather unwilling to cope with anything over 5000 rpm since point float was encountered. He cured this situation by adding more point pressure with the installation of dual springs tailored to 36 ounces of tension. This stabilized the points up to our desired goal of 5500 rpm.
Unusual Carburetor Modifications
At this time, Ak felt the little six was crying for more fuel. First off, with some slight modifications, he installed a pair of vacuum controlled, slide-type, side-draft carburetors. (See July, 1967 Hot Rod for details.) They netted a very fine batch of 10 additional horsepower. Ak described it as. "A setup you can stick your foot in anytime and any place. They don't cough, hesitate or spit back. . . they just GO!"
The added carburetion let the engine belt out a solid 115 rear wheel horsepower at 4800 rpm. Translated into a 0-60 time, this amounted to a 9.4-second clocking (or close to a second off the previous time). A trip down the quarter mile netted 81 mph in the low 16-second bracket
And the car was still capable of a consistent 18-20 mpg at normal cruising speeds.
With the carburetion and cam change, the engine still had a more than reasonable idle at a steady 600 rpm, leading Ak to believe this setup could be used nicely with the C-4 automatic transmission.
After running the engine for 1000 miles, or so, Ak tried another carburetor setup: this time four carburetors with 37mm-size venturis. (See July, 1967 Hot Rod for details.) Ak was very interested in finding out what the small carbs would do for horsepower in the lower range. A reading at 2800 rpm netted 75 horsepower at the rear wheels. At 3800 rpm the net was 105 horsepower, and the top of the ladder was reached at 4800 rpm and 125 horsepower. According to Ak, "This proved that our idea on the soundness of this type of carburetion was right. When you jump on the throttle with these little bears, it is just like having fuel injection. It feels like all the horsepower just unloads at once. In driving the car on the road, we found we could still stabilize idling very nicely at around 600 rpm. This smooth idling was something to behold. We did, however, encounter flat spots in the extreme low end of the rpm range. But, after all, when playing around with 5.8 square inches of carburetion on such a small engine, one must learn to expect that all cannot be 'peaches and cream'."
Ak described the complete modifications as follows: "The general behavior of the car in normal stop, go, and cruising ranges was a most pleasant surprise. Later tests proved this car to be capable of 84 to 85 mph in the quarter mile. With 4:1 gearing and 27-inch rubber, 5500 rpm could be had at any time, and this is 110 mph. This performance proved more than equal to several versions of the 289 2-V and 4-V jobs that we found willing to try on for size.
"We also tried the 4:1 gearing in conjunction with the four-speed tranny, and our conclusions would be to forget this setup since it wreaks havoc with gas mileage and is certainly not conducive to good smooth road speed, at 70 mph. Instead, stay with the three-speed synchro with the 3.20 rear gear set. As for the remainder of the work, take your pick. It all proved very exciting and rewarding for us since we have always felt that true hot rodding is venturing into the unknown or unusual.
I, have personally gained a tremendous respect for the latest version of the seven-main, six-cylinder engine and sometimes wish one could purchase such a package, call it a GT Six, and add some minor heavy-duty equipment to the chassis. This combination would give a good accounting of itself when compared to many foreign sporty jobs that cost considerably more.
"So as we close our hood and roar off into the setting sun, we can only say come on and join the six-cylinder parade for more fun with less money than you could imagine!"
Some of these modifications may affect the car warranty. If you plan to modify, be sure to discuss it with your Ford or Lincoln-Mercury dealer. And of course, the warranty does not apply to any engine that is used in a "competitive" event, defined in the warranty as: "Competitive events shall be defined as formal or informal time trials, competition with any other vehicle, or any abnormal application of stress to the vehicle or the components thereof in a competitive situation."