So the Fresno car is running and I have a brake pedal BUT the pistons are sticking. Not a surprise, and they need to be serviced or replaced (the MC and lines are all new).

Question of the moment is if I can buy a rebuild kit and just deal with the seals or if I'm going to need pistons. Given that they sat with brake fluid in them for 20+ years it seems likely I'll need to order new ones.

Yes/no/maybe? Any experience to share in a similar situation?

I always like to start any new 914 with a full set of calipers from PMB.

Me too but I just bought $900 of bits from Ben and I still need to feed the dog.

(good advice however, and a good SOP)

I have the same problem

PMB has great how-tos and videos on rebuilding the calipers. There is a good chance your pistons are fine and the tutorials walk you through how to set them free and get them looking like new. Mine sat for 35 years and weren't too hard to get apart and cleaned up. My problem was when I sent the shells for replating and they came back roached from too long in the acid. Members here rallied and got me set up with another set of cores I sent to PMB to exchange for replated shells. Rebuilding following Eric's tutorials was one of the more satisfying projects on my build and saves a lot of coin for us DIY junkies.

Thanks @BBrock - the brakes work, just a bit sticky. Will run it (safely) around a big empty parking lot for a bit to see if they free up some. I'd love to just rebuild these rather than have to replace, the 2002tii calipers turned out pretty well.

@Superhawk996 - go go go!

Tom something that has worked for me in the past is to remove the caliper/s take out pads and use a large clamp to retract the pistons fully outwards, reassemble and test.
Another method is put a wood spacer which will stop the pistons over extending and pump them inwards,you can then retract them again as per the above method.
The pistons stick due to a rusty coloured varnish that builds up on them and causes them to bind in the bores,the square section rubber seal cannot do its job of retracting the piston fully when there is no fluid pressure.
If they don't free up its time for a rebuild but this method has worked well for me ,just to add I always vac all the old fluid out and replace with new,I think that helps also.
Good luck.

Thanks mate - appreciate you sharing that.

Hopefully will be driving her this weekend (carefully), suspect they will need to come off.

I say take a run at rebuilding them yourself with the video guiding you along the way. What's the worst that can happen? Send them to PMB if they get all buggered up. But definitely do all 4 calipers. Then flush the heck out of the system.

My 914 was stored for most of the 80's-90's before I got it and the original brakes were fine, I drove them till 2012.
I still have the all but one original lines, proportion valve and the original MC.
I could have even chanced using the rubber lines as they were not swelling, but I didn't.

Storage can vary from the back lawn to indoor and even climate controlled, big part of the difference of cars condition. I store my cars indoors, my 914 is in the heated shop.

I changed everything but the calipers and hardlines (and one of these actually) at this point. Porsche brake systems seem to survive much-much better than Italian and British cars from my experience, but....

Thanks for the responses, will update once I drive the thing on more road-like conditions.