kbengt

On my 73 the hood does not have the functional parts underneath for the scoops, I use it more as a driver & parade car than for showing, is it worth buying the insert and vacuum tubes?

2+2GT

I doubt the "Ram Air" is worth more than 5-10 hp, but it's max cool. You'll need the plenum assembly with valves, and the air cleaner assembly with hood seal, and a hose kit. The 73 351 4V was not available with Ram Air, it wouldn't pass gov't standards. The 73 351 2V was, though, which seems kinda weird when you see it, I mean, a 351 2V Ram Air with single exhaust?

Ram Air:

1971mach1

I have heard that just switching to an open element air cleaner will yield
about the same hp gain as the ram-air setup.

2+2GT

I don't see how. It would be drawing hot under-hood air at all times, but the factory setup draws cold air from above the hood while accelerating.

Standard air cleaners tended to be small, but the 71-73 ram air setups used the same FA-41 filter element as the 428CJ, BOSS, 427, and 289HP.

1971mach1

That's what I've heard from multiple sources. I have no way or desire to prove it on a dyno. They say it's about the same hp gain, if using the stock snorkle air cleaner as a base. Maybe the underhood temp is not really that hot anyway when the car is moving.

By "seat-of-pants" mine felt like it gained about 5hp going from the snorkle to the open
element. I did remove the plastic plugs on the scoops too so maybe that effectivly
lowers the under hood temp. They are almost a straight shot to the element.

Also the factory ram-air setup has vacuum controlled flaps on each scoop which seem like they are there for sex-appeal only because they would just be more restrictive to air flow.

2+2GT

I agree completely that the "stock snorkle air cleaner" is poor. However, the one used with the ram air is very large, not in the same league at all with the little stock one.

Under-hood temp tends to be pretty hot even on the freeway, which is why just about every car on the road now has cold air intake. In 1973, all Mustangs, even the 6 cylinder, had it.

The ram air setup had flaps in it to control the incoming air temp. The carburetor was set up to cruise on mixed air, remember these cars weren't toys, they were meant to be driven summer and winter. The flaps in the hood close during normal driving, to assure the carb won't run too lean (normal intake is through the snorkle and heat riser) and under wide-open-throttle the flaps open to allow cool, dense air in for best acceleration. The shaker ram air cars had something similar. This was common practice in performance cars of the period, the early Trans Am, Chevy cowl induction, etc.

THUMPIN455

Its the temperature difference that makes the car run faster. I did back to back testing with my 70 GTO at the track one day. It has a hood with small scoops right about where a Mustang shaker sits. I have a dual snorkel air cleaner on it, not a RAM AIR setup, just the factory piece.

I flipped the lid and didnt pick up anything in ET or MPH, it just made it louder when the carb opened up. I pulled the scoops that are closed like the stock ones on the 71-73 Mustangs so allow air in and with the lid flipped it picked up .2 in ET and 1 mph trap speed. It allowed cooler air into the carb more than any ram effect because its all open under the hood, no ducting or anything. The filter housing was also about 3" lower than the bottom part of the scoops, so it wasnt shoving air directly into it either, just colder air making more power.

The heat coming off the radiator heats the rest of the air under the hood and that costs you a bit of power. You wont notice a .2 difference in the seat of your pants or on the street, but it is there if you allow colder air into the engine. The GTO would run 13.52 all day long with the hood closed, and 13.50 with it open providing it didnt spin or something off the line. Traps were between 100 and 105 depending on the wind every time I ran that one at the track.

The heat riser is there to help with cold starts and to get the carb off high idle quicker and open the choke to save fuel. Once the engine is up to temp, a heat switch in the intake would open and allow vacuum to close the flapper to the heat riser, at least on some cars like the GTO. I havent seen a stock Ford setup in years, and different engines had different systems. The idea behind all that stuff was to make the cars run a bit more seamlessly, sort of like how EFI vehicles run today just start it up and go without pulling ***** or closing things by hand.

69mach1377

Is it nasa, or naca scoops?

Cruzzar

It was originally NACA (National Advisory Committee for Aeronautics established in 1915) and it was change to NASA (National Aeronautics and Space Administration) in 1958. I'm sure someone will chime in and let us know what Ford officially called them, I'm not sure.

2+2GT