I have a 91 prelude with the B21A1 i bored it 40 over with wiseco pistons eagle h beam rods apr head studs with a copper head gasket intake 2 1/4 in. pipe from cat back gutted the cat titanium valve springs its running about 13:1 compression and my coolant in the radiator keeps building up pressure and boiling into my reserve tank and ive already changed out the water pump, thermostat, all hoses, all sensors and switches for fans, ive tried coolant additives and cant find anything that works so if anyone might have a idea for what might be the problem or a way to fix it let me know.
Aaron

 

whats it tuned on? sounds like you're overheating

 

sorry man but you need a head gasket. at least it sounds that way. it's hard to say YES you need hg, but bubbling in reservoir.....find someone that has the sniffer. it is a tool that detects combustion in the cooling system, using a liquid that changes colours.