will perform Chevette heatercore better?

I have purchased at junkyard this 82 Datsun Cherry heatercore for 6$ :

http://www.watercooling.wz.cz/chladic.htm



but after many chemical calcium stone and paint removing procedures (I used 5% citric acid and 5% phosphoric acid, then paint removing with boiling washing soda), its still about about 0.5 - 1 mm of calcium stone on inner walls

i have quite high water - ambient temp. difference of 6°C, I'm running on Athlon XP 2100+ @ 2357mhz 1.75V, I get these temps at 24°C ambient:
IDLE core temp. 41°C, water 31.8°C, waterblock 34.0°C
LOAD core 52°C, water 34.8°C, waterblock 38.0°C

with one push and one pull 120mm fans at 6V

i tried to get new from Nissan service, but this one costs in Central europe about 280$

have you any idea how to remove the rest of very hard calcium layer? or I will do better with Chevette heatercore? (which I can get cheaper)

edit: Cherry heatercore image from database

nobody knows if new Chevette will perform better than this core? this Cherry core has more smaller fins, so I think, new one performs better (heatercore size is the same, and even Cherry is 0.5" thicker) than Chevette, but my Cherry heatercore is full of calcium stone, which causes higher temp. difference, probably

sorry my worse english


edit: which water-ambient temperature difference you get with Chevette? with aprox. the same setup (100W load / idle, XP @ 2350mhz @ 1.75V)

You could try running some vinegar through it...that's a common trick to remove mineral deposits on plumbing fixtures like faucets, showerheads, etc. It MAY ruin the heater core, (possibly corrosive to the copper), buy it seems you have nothing to lose...