The MGA heater setup includes two small air hoses to direct air to the demister vents, and some larger 4-inch diameter hoses for air intake up front. If you order replacement hoses, they come compressed on length and need to be stretched out longer in the process of bending to fit. The material is thin aluminum with black paper inside and outside, and convoluted so it can be stretched and bent.

The smaller hoses are easily formed and stretched by hand. Essentially, just pull on the hose when you bend it and it will stretch. You need to be careful not to smash the ends of the duct out of round. For this you can put something inside the ends to prevent it from collapsing. The original car setup has a metal end connector on the heater box, and a thick rubber bushing on the demister duct that may be used for this purpose.

There is a 4-inch air duct running from the heater box forward to the radiator mount pipe connector. And another 4-inch duct forward from there to just inside the grille, along with a mirror image duct on the other side to bring cool air to the carburetors. Being larger, these are bit more difficult to stretch and bend but the same principal applies, pull while bending to get it to stretch. I like to lay it across my chest and pull back on both sides. Rotate the pipe and repeat as needed for more stretching.


For the larger hoses, Jim Cheatham in Amelia, VA, USA suggests using a 3-inch PVC female adapter to put into the end to allow bending the hose without distorting it.

With the heater or FAVS installation there will be three 4-inch air hoses, three P-clamps, and one band clamp. Each of the forward air hoses will have a 4-inch P-clamp at the forward end to secure the front end of the hose to the air pan just aft of the grille. The screws for those clamps will be in the front outboard corner of the intake area, close to the body mounting brackets. The longer air hose running from the heater forward to the radiator mounting duct will have a P-clamp midway along the inner fender to hold the bulk of the hose off to the side under the body cowling.

There should be one 4-inch band clamp securing the air hose onto the heater inlet duct. This is thin steel strap with a "buckle" at one end. There is a wind-up pin that looks like a split pin (cotter pin to us yanks). Insert the end of the thin metal band through the slot in the split pin, and wind it up to take up the slack and tighten the band onto the hose (like the wind-off key on the old sardine cans or coffee cans, if you are old enough to remember those).

For the other three hose ends at the radiator diaphragm ports, the factory used washer head sheet metal screws, probably self-drilling type, but it was (mostly) never documented.

Addendum May 28, 2021:
Modern replacement hoses are often just a wee on the small side, nominal zero clearance, and may have internal burrs, but easily fixed. Grab a fat screwdriver handle (or any round stock or wood dowel). Insert the rod into the hose end parallel to the axis and side walls. Move the rod around the inside of the tube in orbital motion pressing gently on the ID near the end of the hose. This will press back any exposed burrs and slightly enlarge the opening by stretching the material a bit.

Addendum June 2, 2021:
For a few years now some replacement 4-inch hoses have been supplied in 100-mm diameter, being 1.6-mm or 1/16-in undersized. This makes them difficult to install on the nominal 4-inch diameter connector pipes, so it may require a bit more fettling with the screwdriver handle to stretch them out enough to fit. This picture from Mark Wellard in Australia shows an OEM 4" hose at top and a recent 100-mm aftermatket hose at bottom (although you likely cannot see the difference of diameter in the picture).

Addendum September 8, 2021:
For those who are tired of seeing the paper and foil air hose in the engine bay get crushed in short time, there is a polymer hose available with spiral wire reinforcement inside, temperature range -60°F to 275°F.
See www.wholesalehoses.com.
Not concours original, but when form follows function this is a far superior product.

Addendum September 10, 2021:
Here is another one, Dayco Autoflex Defroster Hose part number 80175. Internet search finds this one available from a large number of sources like Summit Racing and many local auto parts stores. The Dayco web site may have an error for the inside diameter, but this part number really is 4-inches ID. It has spiral wrap steel reinforcement wire so it won't get crushed. It will be compressed from 6-feet free length to about 28-inches long for smaller shipping package. One 6-ft length is enough to do all three front vent hoses for the MGA. It will be somewhat fleible when installed, may not hold position as well as the original paper and foil hoses, but can easily be pushed aside for maintenance work. Not concours in appearance, but again form follows finction.