The carburetor we used was Ford part number C7AZ-9510-AA and is available from any Ford dealer for $25.60. This is certainly a most reasonable expenditure for an additional four horsepower at this stage of tuning. The air-fuel ratio, by the way, with stock jetting in the new carb, was 13:1. So, we were more than satisfied because a carburetor that can be installed and not have to be rejetted is a rarity when doing this type of work. We should note that this particular carburetor was jetted for use with thermactors. Jet sizes are usually .003 richer on such units.
All This and Economy Too
About this time, our local hot rod club was having an annual economy run and we decided to enter the little Mustang six -not knowing what it would do. Since we had changed the exhaust and carburetor, we were ready to accept almost any figure. Much to our delight, the Mustang registered 35.9 miles per gallon per 200 miles of Southern California coastline. Now before you call me a liar, let me explain that 50 pounds of air was used in the tires (for low rolling resistance), and coasting was allowed whenever possible. The overall average speed was 45 miles per hour and the gas tanks were sealed. The nearest competitor registered 27 mpg. The cars were all carefully inspected for obvious infractions such as added gas tanks. etc., and when the final results were in, The Mustang was able to keep its reputation as an economy winner while performing with 90 hp (at the rear wheels), compared to the 65 hp it started life with.
Increasing Compression Ratio
Our next step was to increase the compression. To do this in the most economical manner, head milling proved to be the only way out. Since we were still getting such fantastic mileage, we felt we could well afford premium gasoline, so we decided to mill the cylinder head .060. The standard head cc'd at 54. After milling .060, it was 44. Standard compression ratio was 9.2. After the head was milled, the compression ratio was 10.5 which gave us an accepted ratio for average high test fuels.
increase in the torque of the engine. It would literally want to lie on its side during fast acceleration. This little six-banger with a light flywheel and clutch grabs rpm like a full-house 289.
Comparison Performance Run
We were so impressed by its performance that we immediately decided to go out and run a series of acceleration checks so that we might compare our revitalized Mustang with the current crop of six-bangers offered by other manufacturers. The accompanying table compares our figures on the Mustang six with road test figures (found in leading automotive publications) for the Camaro and Barracuda.
Seven Main Bearing Durability
At this point, someone is probably asking the question, "How long will it stay together?" My answer is, "Forever!" This six, unlike earlier engines, employs seven mains and has enough bearing area to support the Golden Gate Bridge. The size of all the rotating and reciprocating parts add up to but one conclusion: It is the most rugged six-cylinder engine that has been offered on the market for many a moon, and it has durability with a capital "D."
Performance and Economy
The behavior of the car at this point was every bit as good as it was in its stock form. We had increased horsepower from 65 to 100 at the rear wheels, yet had lost none of the economy or smoothness of operation inherent in this particular car. In fact, the first comment by people driving it is. "It just has to be an eight-it's too smooth." With a 0-60 time that will give its big brother a hard row to hoe, one can only say that changing of the car's personality had been well worth the expense and effort. After all, getting the gas mileage this little bear gets, we can save money we spent on the performance goodies in short order.