Adelaide's old "red hen" trains will be back on the rails between the city and Port Adelaide this weekend.

Bob Sampson of the National Railway Museum at Port Adelaide told 891 ABC Adelaide the museum was being inundated with phone calls this week from people keen to make the trip.

"I think [it is] because they were a part of Adelaide and suburban rail transport for such a long time — from the early 1950s right through to the early 1990s — that's a long time and lots of kids went to school on them and people went to college and uni and they've just been a part of Adelaide's scenery for a long time," he said.

"It's rare that we're allowed, in conjunction with the Department of Transport, to get these things out on the main line and run to the city, so it's a fantastic occasion."

The old red trains will run seven return trips on Saturday, and the same on Sunday and buying a $10 return ticket will also give people free entry to Port Adelaide's three museums — rail, aviation and maritime.

Mr Sampson said a lot of work was needed to put the old railcars back on the main line.

"There's a whole lot of planning, there's rail safety regulations ... it's quite a lot of logistics involved. There's about 10 inches of paperwork to satisfy compliance issues and mechanical issues and insurance issues," he said.

"They're precious little things and they cost a bit to run but all in all it's great to have them out for special events."

Trains will use a rusty 'secret' line

He said the "red hens" usually ran on one kilometre of special track at the rail museum but there was a way to fairly easily get them from there to the main line.

"We've got a secret little track that comes on near the Grand Junction Road bridge down there at Port Adelaide," he said.

"It's a bit rusty but we try to use it as much as we can."

Adelaide Metro is the main rail operator and its drivers must be used this weekend.

"There's been a hand-chosen half dozen drivers, who used to drive them a long time ago, who've had their refresher training," Mr Sampson explained.

"There's always big smiles on them when they drive them on the main line."

The old trains will run hourly trips this weekend between the city and Port Adelaide and Mr Sampson said each service could carry up to 160 people.

He said tickets would be sold at Adelaide Railway Station or at the National Rail Museum.