im starting work on a new head and i want to measure my progress without spending a fortune , i was wondering if i connected a hoover to the valve end of the ports and a carb balancing tool to the other end would this work to measure any flow increase or would the hoover be too powerfull ?

hmm, interesting. whether it would give a decent reading i don't know, but i think a hoover will give the same amount of suction as a running engine at idle would. can't harm to give a shot

You need to be able to measure pressure drop across the head and the airflow to get a meaningful figure. Normally the airflow is set to give a constant pressure drop across the part you are measuring. Airflow can be measured by measuring pressure drop across an orifice of known diameter, which is how most of the DIY type flow benches work.

http://www.kartingtechinfo.com/tech/flow.htm
http://www.ag.auburn.edu/users/parmega/articles/flowbench2/
http://performancetrends.com/ez_flow_system.htm

It'd probably work as a comparison tool for balancing purposes...