I started pulling apart the A12 sitting in the garage to rebuild it this morning (i'm a noob, never built an engine before) and found some rust in one of the bores. Was just wondering if its still possible to use the block, or if I should start looking for another to use.

id say u could cann,can u still get the pistons out? depending on how deep its eaten in,if it hasent been bored already it may b ok if its already been done u might have a problem.take the crank and pistons out and take some better photos of the worst afected areas then go from there

that looks bad

looks like it has had water sitting in there for a while...

I cant see why the piston wouldnt come out, I can still turn the engine by hand but it wont turn any further past the main ring of rust, and below that the metal is nice and clean so whats in the pic should be the worst of the rust.

the engine has been sitting for a while, and the affected areas are now being soaked in wd-40.

I had exactly the same problem recently with a A12 rebuild I was doing of an A12 that had been sitting in the elements for a few months.

I just had to hone the cylinders and they came good again.

I took lots of pretty pictures and put them on a website

http://mildman.datsunprojects.org/

Check it the A12 strip and A12 reassembly bits.

My pistons were stuck in the bores solid and I managed to get them out, clean them, re-hone the bores the pistons moved nicely...although I never did a compression test the pistons seemed to be pushing the air nicely.

just had a look at ur site, damn thats some nasty rust!!

I was able to get the engine to turn over fully by turning the crank nut with a shifter and a little effort so getting the block prepped should be no problem.

Sounds a lot better than the A12 I tackled then....it took a ####load of work just to get the pistons out of the bores!

If you can get the engine turning over I'd say you will be OK - but one of those engine hone tools are only about $50, and as long as you have a drill the honing process can be done pretty easily.

The hone only takes tiny fractions of a mm of the sides of the bore.

Good luck