If you wrap the dash-top vents with duct tape (or similar), you can step them up to 1.5". After that, there are a few options:
Convoluted alumium ducting is commonly available from car airconditioner repair companies, though unfortunately only in 50mm (2) outside diameter. The 50mm ducting can be made to fit by slitting and either bending in the end of the duct (to reduce diameter and fit inside the rubber demister outlets) or bending out the end of the duct (to increase diameter and fit over the end of the demister outlets. The demister steel nozzles can be increased in diameter to match the 50mm duct by wrapping them in duct tape until they are an interference fit.
40mm outside diameter convoluted aluminium type ducting tube is stocked by Fuelmiser (part number PHD-40ML - available from Supercheap), though unfortunately only in 1 lengths. Contact with the Fuelmiser technical team indicates that they are not able to source longer lengths.
Clark Rubber stocks Flexi-flo Hose in different sizes (25, 30.5, 31.5, 32, 35, 38, 44, 50, 63, 76 and 102mm ID). This is a black EVA stripwound hose similar to a vacuum cleaner hose, except designed for Industrial use. The following two sizes are likely to suit:
30.5mm 31.5mm
Inside diameter 30.0 31.0
Outside diameter 39.0 41.0
Working pressure (psi) -5 to 50
Working temperature (ēC) -20 to 60
Note however that the maximum working temperature is 60ēC, which could be close to the heater air temperature (a 7psi radiator cap means that the water temperature inside the heater water-side can reach 111ēC the air will be cooler than this though). This product is also stocked by Hoseonline (P.O. Box 3027, Mentone East 3194 Victoria, Australia,
http://www.hoseonline.com.au, telephone 1300 577 731).
This mob does longer lengths of the 1.5":
http://www.holden.co.uk/displayproduct.asp?sg=1&pgCode=083&sgName=Electrical&pgName=Heaters+%26+Electrical+Fans&agCode=0210&agName=Heater+Accessories&pCode=080.519Cheers,
Harv (deputy apprentice heater fiddler)
