Quote: barometric corrections on an SF-110??? no mention of that in my owners manual...
as for the valve job deal.....i'm pretty "bread and butter" in that dept, and i re-do the valve seats more to make sure they are concentric than for any big gains in flow. i usually do a std 3 angle on the intakes, along with a bowl cut, which gets blended into the bowl. the exhaust usually gets a two angle/radiused bottom cut.....pretty much like what comes on most aftermerket heads these days.
Dwayne,
Yea on the Barometric thing, .. keep an eye on it and track it, .. try a test with your calibration plate on a 28" day VS a 30" day, .. it makes a difference, well does on my bench. Keep in mind the SF-110 isn't the same design as say the SF-600. The SF-600 nun or this stuff matters much.
You are right in that THE most important correction on the SF-110 is temp for accurate CFM numbers.
Valve jobs, .. The most important thing a head porter needs to work on, .. even before grinding. Performance valve jobs on the intake need at least 4 angles. top, seat, bottom and an angle below the bottom that does or doesn't get blended. Dwayne, your 3 angle with a bowl cut sounds similar to what I do, .. 4 angles if you count the bowl cut.
Several things can be done with the angles on the VJ. Top and bottom angles play a huge roll in the low lift flow curve and plays a roll in the entire flow curve. Every head and every level of porting needs something different.
Think about this, the largest restriction to flow is the curtain area at the valve opening, .. and the efficiency the cylinder sees at that opening has a huge effect on power. By making the, say bottom 60º angle wider you can fatten up the low lift flow, .. or make it very narrow, .. but make your 70º wide and don't blend it into the bowl, .. you can make a fat low lift flow but also make flow over .400" take off.
Same goes for the exhaust, .. top angle, seat and a radius, .. but different radius' will change the flow curve. Low lift flow, big / round radius, .. high lift flow, wider top cut & smaller radius .. ..
Some of the aftermarket heads need a 50 or 52 or 55º seat, .. anyone doing that?
You'll notice if you track the curtain area flow coefficients that the more you open the valve the less efficient the flow is, .. this is where custom seat angles come into play.
