Had to use search to find my own thread
OK, lived without heat last winter, lived w/o AC this summer, decided I needed to get cracking and git this sucker in/working before the weather turns yet again...
Picked up a NOS BN2 awhile back, cut the holes out from the late model install manual pattern, and was stymied trying to find factory ductwork w/o buying a complete system, as it seems most folks who yank these just grab the heater, and leave most of the essential goodies required to install it.
Bought some flex hose--- IMHO too delicate for survival in the trunk with other junk, and doesn't flow well.
Notes on the install add some things I figured out...
Install is still a work in progress, but it's working.
Exhaust is extended with a tapered 1 5/8" tube, sealed and clamped with many layers of Tiger seal and a couple hose clamps.
intake is 3/4" heater hose.
The exhaust holes were originally drilled for the BN4, and it is still an option If I go with larger 5" ductwork.
BTW---Coffee cans (metal ones) are ~perfect size for the inlet and outlet on a BN4 for fabbing custom ductwork.
A BN4 has the advantage of having spark ignition and being "throttleable" via an adjustable exhaust thermostat from 1000-4000 kcal/hr.
A BN2 only has a glow plug for ignition and is 2000 kcal/hr., fixed heat output, cannot be cycled on/off gracefully.
The glow plug is only "on" until the unit lights off fully, then the flame is self sustaining.
If a BN2 flames out, it will restart the glow plug and try to do a hot start, but you may get some "bangs" if you don't allow it to cool down/purge first.
A BN4 has a spark plug with integral glow wire, and has no problems cycling on/off to vary heat output.
Did some more browsing and ended up with this for duct:
It does NOT hit the car/gas tank no rattles etc. Fits ~like factory, clears the little kickout in the front for the factory heater duct.
Note:The intake air and hot air connection points to the car are reversed since I have an under dash AC unit to blow the heat around.
(AC now done yet, but works for this for now)
Making a cover for the rig out of some scrap electronic enclosures:
(only the front part so far cut out, U shaped, slides under the duct/heater with cutouts for the ex pipe intake fuel pump etc)