Jim Smart
August 7, 2005

Cowl And Window-Leak Fixes
This is likely the greatest challenge you'll face with a vintage Mustang driven in all types of weather. Mustangs from '65 to '68 suffer badly from leaks, and windshield and rear-window rubber gaskets tend to leak a lot. As they get older and dry rotted, they only get worse. With the windshield and rear window, begin with new rubber gaskets and load them up with plenty of butyl sealer between the rubber and glass, and between the rubber and body. It's a messy job, but it has to be done if you intend to drive dry. Lay down plenty of sealer between the rubber and body right before you install the stainless trim.

Cowl-vent leaks present an even greater challenge. For one thing, Mustang cowl vents didn't have any kind of corrosion protection outside of galvanizing on the bottom half of the cowl assembly. The only permanent fix is to split the cowl assembly, drill out hundreds of spot welds, then perform the repairs, protect the steel with a good self-etching primer/sealer, seal it up, and weld it back together.

A short-term fix is the plastic cowl-vent hats that fit inside the cowl dams, which will keep moisture off your feet. If your Mustang's cowl suffers from serious corrosion and rot-through, you'll have to undertake a major cowl repair to permanently fix the problem. The Mustang aftermarket also offers a clip-on cowl-vent cap that keeps out rain and snow, and also keeps air out when driving. Clip it on when the rains come and remove it for the sunny drives.

Long-Tube or Shorty?
We get this question all the time: long-tube or shorty headers? Long-tube headers offer better performance. Shorty headers offer a cleaner trek to the exhaust system, but don't give you the performance of a long-tube header. Long-tube headers tend to get in the way of power steering and make for a hot ride in the summertime. For the daily commute, we suggest shorty headers or the leaner, cleaner Shelby tri-Y headers with Jet-Hot coating, which keeps the heat inside. They also cool off quickly when the engine is shut off.

Coolin' It
One thing we tend to fear most about driving a classic Mustang daily is overheating, especially during summer's warmer temperatures. It's inconvenient and not good for our image. A boilover in a classic Mustang is anything but cool.

Cooling systems are one of the most overlooked elements of our Mustangs because we don't see the immediate benefit, at least not until we're in trouble. To avoid problems, begin with a new high-capacity radiator, a cooling-system filter to catch the rust and iron particles, heavy-duty hoses (all of them), a 180-degree thermostat, a super-efficient cooling fan (mechanical or electric), proper water-pump-pulley sizing, a high-flow water pump, a fan shroud (where possible), proper cylinder-head-gasket installation, clean water jackets, a clear heater core, and the right antifreeze/water mix.

We suggest a good aluminum radiator fitted with a fan shroud. If you desire copper and brass, opt for a four-row desert cooler with the fan shroud. Not enough of us use a fan shroud, but it keeps air velocity moving through the radiator tubes, which removes heat. A cooling-system filter goes in the upper radiator hose to collect the rust and iron particles from a fresh engine build. This keeps them out of your new radiator. The filter has to be checked and cleaned periodically.

Theories abound about what kind of thermostat to use. For '65-'73, Ford suggested 180 degrees, which hasn't changed in 40 years. Classic Mustang engines are happiest at 180 degrees coolant temperature. As a rule, 160 degrees is too cool and 195 degrees is too hot (except in computer-controlled applications). Never run your Mustang without a thermostat. In traffic, it will overheat. On the freeway, it will run too cool, except in hot weather, when it will boil over.

Always opt for the best radiator, heater, and hoses (including the bypass hose). Make sure there's an anti-collapse spring in the lower radiator hose. Without the spring, the lower hose tends to collapse at highway speeds, cutting off coolant flow to the engine and causing a temporary overheat until you get off the interstate.

Pulley size is important. A water-pump pulley that's too large will turn the water pump too slowly. By the same token, a pulley that's too small will spin the pump too fast. Use V-belts that fit the pulleys properly. Always exercise proper belt tension: half an inch either way. Belt slippage is a one-way ticket to an overheat. If you're going to use an engine-driven fan, the best choice is a thermostatic clutch fan, which engages only when your engine needs it. Next is a lightweight aftermarket flex fan, which flows lots of air at idle and flattens out for efficiency as engine speed increases.

Electric fans, when sized properly, do a splendid job. They only come on when the ignition is on and the engine is hot.