about 9 or so years ago when i was 19 years old i had been into small blocks and working on them regularly for 5 years or so. i had also ported a set of double humps for my shop teacher while in high school at 16 years old, it actually turned out well and my heads actually picked the car up .2 tenths or so in the 1/8th if im not mistaken. i was building a 383 by the time i was 19 for my 67 chevy pickup. i was a member of chevytalk during this time asking as much as i could to learn as much as possible , i had read david vizards entire series of books on small block chevys including "how to build and modify small block chevy cylinder heads" from front to back a hundred times. i broke down and bought a set of pro action 200cc heads for 800 bucks which was alot of money for a 19 year old kid. decided to port them myself, raised the port roofs, narrowed the guide boss, paid extra attention to port bias,blended short side radius and cleaned the runners up some not touching the opening of the intake ports at the gasket surface.also raised exhaust ports slightly, narrowed the guide boss and widened the port taking material away from the busy side of the port. i didnt port these heads to the max by any means. my data on stock pro action 200s with 2.05 valves was 240-245 cfm @ .600, high 170s on the exhaust at .600. i had my heads flowed and ended up with a 215cc(very close to this, cant remember exactly . head that flowed around 290 on the intake side at .600 and my exhaust ports were around 195 or so if im not mistaken. ofcouse these are just figures for .600 lift not taking into account low lift numbers but the head improved all the way across the board. the porter who tested my heads thought i had done a good job and i feel i had at that point as well. months later i still hadnt put the heads on anything and i became ancy thinking book knowledge could replace experience i went deeper into the cylinder heads this time around (before they had even been run) and did a full port job on them. had them sent off and flowed on the same bench by the same person. he told me he had good news and bad news. the good news was that my flow at .600 lift from 315 cfm , i was around 210 on the exhaust. my intake port was now 224 cc or so. the bad news is that the turbulence in the port was so severe that he said the time he wouldve had to invest in fixing them for me wouldnt have been worth it and that was assuming he would have been able to sort them out anyway. i know this is a long post but i just want to share my experience for anyone thinking they can do a full port job with out a flow bench and years of experience. had i stayed with my basic port job the first time around i wouldve had some decent heads that wouldve suited my 500hp goal with a 383. instead i had two lumps of junk. PLEASE do not attempt to go beyond your skill level as i did. do a basic port job as grumpyvette would suggest, if you want to get the most out of the heads find someone with a flow bench and good reputation. Book knowledge doesnt equal actual knowledge in some scenarios.
having 315 cfm of flow at that lift range is great, but if the quality of the flow is poor you are only hurting performance. like i said, sorry for the long post, but if someone actually reads this all and decides not to go grinding on a thousand dollar set of heads because of this cautionary tale then its worth me typing it out. good luck to everyone
having 315 cfm of flow at that lift range is great, but if the quality of the flow is poor you are only hurting performance. like i said, sorry for the long post, but if someone actually reads this all and decides not to go grinding on a thousand dollar set of heads because of this cautionary tale then its worth me typing it out. good luck to everyone
