Head Porting basics

I open all my heads (bowls) to 88% of valve diameter, bikes too. Have for 20 plus years and they work very well with that. Some Pro stock head builders use as much as 93%. That doesn't leave much under the seat to support it, but they are torn down every week. I use 85% for dailey drivers. I have a Suzuki (16 valve) that I built in '97 and I opened the throats on that to 90% and it is still running strong. You can have your machinest use a 'bowl hog' to open your bowls to your specs. They do a great job and is a very inexpensive operation to have done while the seats are being freshened. Works for me , the flow bench likes it too. JMHO.

Terry