it could be that you've got alittle rust in the water jacket and you might not of rinsed out the block quit enough to get all the soap out. flush your system and try again. no
antifreeze. just water and waterwetter. see what happens. i am not a fan of
antifreeze anyway. racetracks dont like it. it stinks it stains and unless you park outside in below freezing temp. you dont need it. water and waterwetter!