It appears that to get maximum heat to come into the cabin, I have to roll the window down about 2 inches.
The open window must create a draw like a chimmney flue.
Do all 914;s ahve this same situation ?

Well the window helps from getting affixiated. Having carbs and a CB vent box I tend to make some nasty air which gets sucked into the fan and blown through the heater.
Makes sense to get more air flow through the car to have the window open a smidge.

QUOTE (Joe Ricard @ Oct 12 2005, 08:06 AM)

Well the window helps from getting affixiated. Having carbs and a CB vent box I tend to make some nasty air which gets sucked into the fan and blown through the heater. Makes sense to get more air flow through the car to have the window open a smidge.

Ahhhhhh, another carb conversion "PLUS". The Cap'n

Mine works about the same. If you are trying to blow into a closed cavity, some air must exit the cavity (the fan is not capable of pressurization).....so cracking the window allows for this.

QUOTE (Cap'n Krusty @ Oct 12 2005, 08:19 AM)

QUOTE (Joe Ricard @ Oct 12 2005, 08:06 AM) Well the window helps from getting affixiated.  Having carbs and a CB vent box I tend to make some nasty air which gets sucked into the fan and blown through the heater.   Makes sense to get more air flow through the car to have the window open a smidge. Ahhhhhh, another carb conversion "PLUS". The Cap'n

It won't matter soon enough. just put the money down for a Tangerine header.
Only you Yankees need heat anyway.

QUOTE (Joe Ricard @ Oct 12 2005, 09:39 AM)

QUOTE (Cap'n Krusty @ Oct 12 2005, 08:19 AM) QUOTE (Joe Ricard @ Oct 12 2005, 08:06 AM) Well the window helps from getting affixiated.  Having carbs and a CB vent box I tend to make some nasty air which gets sucked into the fan and blown through the heater.   Makes sense to get more air flow through the car to have the window open a smidge. Ahhhhhh, another carb conversion "PLUS". The Cap'n It won't matter soon enough. just put the money down for a Tangerine header. Only you Yankees need heat anyway.

Oh well...at least we don't need "water wings"

There's a good size vent hole from behind the passenger and driver seat to the door jamb-and a plastic filter/insert in the dorr jamb hole...

Was that intended to relieve the pressure inside the cabin? or does it have another use ?

QUOTE (jim_hoyland @ Oct 12 2005, 12:42 PM)

There's a good size vent hole from behind the passenger and driver seat to the door jamb-and a plastic filter/insert in the dorr jamb hole... Was that intended to relieve the pressure inside the cabin? or does it have another use ?

If you pull the back pad you'll see that it just vents right back into the car.

QUOTE (jim_hoyland @ Oct 12 2005, 03:42 PM)

There's a good size vent hole from behind the passenger and driver seat to the door jamb-and a plastic filter/insert in the dorr jamb hole... Was that intended to relieve the pressure inside the cabin? or does it have another use ?

early cars don't have the plastic guard that's probably intended to keep body parts from getting stuck in there and causing lawsuits. removing it might improve the flow (yes, that's what it's there for...). i've never really done an A/B test because i have owned only early cars, and /6's make plenty of heat, if the heater box hoses are intact.

i've always thought you could improve vent extraction my adding a 'Gurney flap' to the back of the door handle. but like i said, i've never tested it in the wind tunnel of life ...

QUOTE (jim_hoyland @ Oct 12 2005, 01:42 PM)

There's a good size vent hole from behind the passenger and driver seat to the door jamb-and a plastic filter/insert in the dorr jamb hole... Was that intended to relieve the pressure inside the cabin? or does it have another use ?

I thought they were there to trap water and assist in the rusting process.

The heater system is a non-recirculating system, much like that used in the VW Bug. I recall the early VW Bug the VW owners manual stated to achieve fastest window defroast one must open the window a little bit. It was because the car is pretty air tight, and small. The fan blowing into the cabin from the engine bay will "back up" and not flow as much air if the cabin is totally sealed. By opening the window a little you are doing what VW recommended 45 years ago.

I have noticed the same thing on my 914s, and will get more heater air with a window open a bit. I do not recall ever seeing this method of improving defroast in any Porsche owners manuals, However it does work.

FWIW, I don't have heat hooked up (no flex hoses connected to the hard tubes that go behind the rockers). I noticed that when I rolled my window down a smidge, that the burnt oil smells in the cabin increased slightly. SO I decided that there must be a draw like you suggested. Maybe I'll remember to cap off those tubes someday...