The Grumpy Grease Monkey mechanical engineer.
you should watch all the way through all five videos
there seems to be a wide variation in the quality of the machine work being done
in many cases and the heads obviously vary in quality of machine work from various sources
this has always been the case, a good skilled machine shop makes a huge difference in the quality and durability,
of the cylinder heads you receive and how durable and dependable they will be in use!
any idiot can slap parts together on a cylinder head,
but it takes an experienced machinist to do a decent multi angles valve job and check clearances on the heads.
and as always you tend to get what you pay for and higher quality heads and components do tend to cost more.
more port flow related info
links, calculators and info well worth reading thru, yes theres a HUGE tendency to breeze over them, but they contain a ton of related info youll need USE THE CALCULATORS, YOULL, QUICKLY FIND THE LIMITATIONS http://www.rbracing-rsr.com/runnertorquecalc.html...
sellecting valve springs, and setting up the valve train
How do you determine the spring pressure needed to keep the valves under control for a given lift, duration, and max rpm. It might take you several hours to read thru all the links and sub links but its time very well spent as it could save your engine from destruction and save you thousands of...
valve train clearances and problems
you might want to read thru these links and sub links it will help you avoid costly mistakes http://www.summitracing.com/parts/pro-66830/overview/ https://www.harborfreight.com/multipositional-magnetic-base-with-fine-adjustment-5645.html...
valve seat angles and air flow
valve seat angles and the actual angles cut on the valve edges them selfs and how you have the area under the valve in the port bowl area cut and blended has a marked effect on your engines air flow. as a general rule air flowing over a change in angle across a surface tends to become noticeable...
tumble and swirl, quench & squish
I could fill chapters on these subjects, but its basically not something the average engine builder assembling off the shelf parts needs to be overly concerned with other than to understand the potential power may change due to the parts selected and the careful assembly and measurement during...
multi-angle valve job related
for a valve to function correctly it needs to both seal completely when seated against the head and allow efficient flow between the valve seat and underside of the valve as it lifts off its seat, the curtain area( that's BASICALLY, the distance the valve is off its seat times the valve...