Carbon canister on top of fuel tank Options

[356drb]

The fuel tank change occurred in April/May 1974. The carbon canister moved off the top of the fuel tank prior to this change. Was it at the end of calendar year 1973 or at the model change in the summer of 1973?

[wonkipop]

@starbear , sounds like your car sat around or was delayed?

mine has jan 26 production build date and is vin sticker 01/74.
in and out the door quick.

expansion tank is still steel, cannister is in engine bay on back trunk firewall.

change to a plastic expansion tank would be a simple matter on production line as it is an almost identical component made of a different material. could happen any time stock of new component came in.

changing charcoal tank location is more a build, assembly sequencing matter, and though it looks simple, enough is involved to brief workers on how it is to be done and to make sure the first installations go smoothly/correctly.

can't help think original cannister tank up front might be a production rationalisation/packaging legacy of accommodating 914/6 production. cars sent from karmann factory complete as possible with tanks and plumbing? tanks, cannister etc are as far as i know identical on 4s and 6s. original design considerations meant the best place for both cars was up front and not in the 6 engine bay?

as an aside, fairly sure euro spec cars don't have closed loop evaporation system.

to do 74 cannister change they had to alter the grommet in the tunnel/front fire wall to have a third small hole to take the fine line to the tank and an extra hole and grommet into the rear passenger firewall to take the same small line through the central tunnel from the engine bay.

also its not hard to imagine the system works better with the cannister closer to the engine fan bleed pushing the fumes out of the cannister into the aircleaner for burning.
shorter distances.

given that they did not need to deliver body shells to porsche after 72, it is surprising they did not do this change sooner in 73 or at the 73/74 model changeover when production would have halted for vacation.

maybe they had to get certification/approval from usa/california EPA/DOT bureaucracy and it delayed things? a fuel evaporation control system might have been a touchy area of regulation in the 1970s.

[StarBear]

@starbear , sounds like your car sat around or was delayed?

mine has jan 26 production build date and is vin sticker 01/74.
in and out the door quick.

expansion tank is still steel, cannister is in engine bay on back trunk firewall.

change to a plastic expansion tank would be a simple matter on production line as it is an almost identical component made of a different material. could happen any time stock of new component came in.

changing charcoal tank location is more a build, assembly sequencing matter, and though it looks simple, enough is involved to brief workers on how it is to be done and to make sure the first installations go smoothly/correctly.

can't help think original cannister tank up front might be a production rationalisation/packaging legacy of accommodating 914/6 production. cars sent from karmann factory complete as possible with tanks and plumbing? tanks, cannister etc are as far as i know identical on 4s and 6s. original design considerations meant the best place for both cars was up front and not in the 6 engine bay?

as an aside, fairly sure euro spec cars don't have closed loop evaporation system.

to do 74 cannister change they had to alter the grommet in the tunnel/front fire wall to have a third small hole to take the fine line to the tank and an extra hole and grommet into the rear passenger firewall to take the same small line through the central tunnel from the engine bay.

also its not hard to imagine the system works better with the cannister closer to the engine fan bleed pushing the fumes out of the cannister into the aircleaner for burning.
shorter distances.

given that they did not need to deliver body shells to porsche after 72, it is surprising they did not do this change sooner in 73 or at the 73/74 model changeover when production would have halted for vacation.

maybe they had to get certification/approval from usa/california EPA/DOT bureaucracy and it delayed things? a fuel evaporation control system might have been a touchy area of regulation in the 1970s.

Yeah, probably delayed a while, maybe because it has the appearance group and needed a new supply of the special parts. For whatever reason, mine has many 73 parts (seats, gas tank, center bumper panels black not chrome, etc.)