So how much difference in performance does this make!!!

I have a Porsche 911 engine in my bus running a fully stainless custom exhaust. Two 3-in-1 headers into a back box. I am weighing up replacing the headers with heat exchangers.

the reason, the bus is back in the uk where some heat would be useful for the majority of the year. I have a propex gas heater that i have plumbed into the stock Y pipe, but due to the sheer length of the ducting system there is no back pressure left in the system so heating is pretty non-exsistent. My only feasbile option is to possibly source an inline fan to boost, or put heatexchangers back in.

now the bus isnt used for track or 1/4mile action, but I was wondering what the performance difference would be between running stock heatexchangers and effectively Jtubes???

maybe some of you drag racing guys would be best positioned to know?

NaFe

Just a thought. A lot of guys reckon that a stock heater setup does squat anyway without a fan as the air has cooled by the time it gets to the front.
Maybe try the fan in line first and see from there if you still need extra warmth.
You can also put in heated seat pads but that involved removing the covers which would be about as much work as fitting the exchangers.

For the record, I think stock late bus heaters work ok, just most are incomplete in some manner, as for Mr Porschekombi, stock 911 heat exchangers flow awesome, they are probably very similar or the same as what you have presently, 2x 3-1 with sheet metal casing over them. I don't see the problem. It takes an absolute awesome system to out perform the stock Porsche system.
as mentioned tho, an inline fan is a symple addition.

[EDIT] just noticed you said yours is presently S/S so there's a difference, but the stock merge is beautiful.

the exhaust will be restricted to a certain amount as it will be going through the fins as opposed to the larger exhaust manifolds. i would also have to buy the other components like a blower and piping etc. it would end up being a bit of a custom jobby. i'm thinking using the type 4 hot air heater blower supplying the flow. this could then be adjusted by a potentiometer...i may be able to use a VW headlight switch, utilizing the dimmer for the instrument cluster back light...or simply an on off switch lol

The early heater boxes I have experience with are pipes inside a tin housing so maybe you can get an earlier set that are less restrictive? I thinkr h/light dimmer would burn out with the load of a fan on it, maybe you can get a high wattage potentiometer....??