Jeff, For the intake I like a 60 bottom, 45 seat and anywhere from a 15 to a 30 top cut. Now those angles are not to different than what most will use when the do a valve grind. But... there is a key to good intake flow... and that is the width of those cuts. I like to see the width of those cuts to be minimum of .080 wide. To do this you will need the venturi or cross sectional area under the valve to be 88to 89% of the valve head diameter. Doing this will also allow me to go in and put a 70 degree bottom cut which helps slightly. Therefore.. if you have a 2.125 valve then you would need a venturi (or the diameter of the bottom cut opening) of 1.870. 2.125 x .88 =1.87. If you go 90 to 92% witch is 2.125 x .92 = 1.955 then most of your hardened valve seat will be gone and therefore the width of the angles will be rather small. I hope this makes sense. On the exhaust I like to use a radius cutter with a 45 seat. I have ported several sets of cylinder heads over the last 5 yrs and this will yield 10 to 15 CFM more than a 60,45,30 combo. Again... the venturi must be around 88 to 89% of the valve head diameter. Back Cutting the intake valves.... on the intake side I use a 30 degree backcut. The last set of cylinder heads I did a backcut netted 8 cfm @.100, 12 cfm @.200, 9 cfm @.300, 8 cfm @.400 9 cfm @.500 and 1 cfm @ .600 lift. Back cutting the exhaust valve.... depending on the back angle of the valve this could hurt flow. Your combination should be tested on one valve first. I have seen this go both ways. Therefore its better to do one valve first instead of all 8. Valve Margin.... this is the flat side of the valve or the width of the flat on the OD of the valve. On the intake its best to have a valve margin of .080 to .100. On the exhaust I like a radius on the margin. Most Ferea exhaust valves are delivered with a radius margin. Short turn Radius.... this is an easy one guys.... got your valve and wrap a coat hanger around the outside of the valve. This is now the shape of your short turn. I hope this helps!!! Later.... :3gears:
Thanks for the info john. Do you know what the back degree is on your Ferrea valves? As in a nail style or tulip valve. I would like to try a few different style valves to see if it improves flow. My head guy says the reason why the flow falls off after .650 lift is because of the short turn is too steep and the port runner height isn't high enough. We need a tall head with 6+" long valves.
Flowsheet Here you go Chris. I don't remember if the exhaust is with or without pipe, but it is almost untouched, so I am sure you will be able to tell. And since you are interested in the intake anyway...
