or u can get a custom made Copper radiator, expensive but better heat dissipation.
There are also custom aluminuium radiatiors with metal tanks instead of plastic.
Only a machine can tighten the teeth to seal plastic tank onto aluminium core.
Our desi ustaads use silicon in addition to rubber gasket, which provides temporary solution.
further more they so pressure testing powered by lun-gs which is nothin in comparison to what a combustion engine can produce.