Smitty describes the aerodynamic benefits of multi-angle valve jobs, increasing airflow and therefore horsepower by simply "knockin' off some corners."
While you covered the 15 degree incremental changes in angle to maintain laminar flow over the valve seat and face, you didn’t mention that the 15 degree changes in angle function to provide vaporization ridges, to provide additional fuel - air atomization, and is why radius cuts are not typically used. It’s always left me going huh?, for how much OEM’s leave on the table, for lack of attention to details, for gains in reduced emissions, increased mileage, as well as performance.
That's a nice addition! It's a "Goldilocks challenge" to have good turbulence for atomization, but not so much turbulence that the flow into the cylinder is compromised.
Well said. The tumble and atomization create a good mixture that achieves a faster burn rate (good for performance & efficiency). The biggest factor for us, as a supercharged engine, is getting maximum flow rate through the valves.
Agreed. To be more specific, the *seats* may have 3+ angles, but valve face is usually 2 angles, one being the angle of the valve face contact area, and the second being the backcut angle up to the stem. There's some good pictures and data at johnmaherracing.com/tech-talk/3-angle-valve-job/
Interesting idea! This sounds like it would reduce the concentric contact area between the valve and seat. That contact area is a critical thermal path, especially for the exhaust valve, so the valve could run hot. It may be pounded into submission to match the angle of the seat over time.
I love that i found this channel, it's so hard to find people that actually know the logic behind performance. Thank you 🙏💯
just got the multi angle job done looking forward to try it out
While you covered the 15 degree incremental changes in angle to maintain laminar flow over the valve seat and face, you didn’t mention that the 15 degree changes in angle function to provide vaporization ridges, to provide additional fuel - air atomization, and is why radius cuts are not typically used.
It’s always left me going huh?, for how much OEM’s leave on the table, for lack of attention to details, for gains in reduced emissions, increased mileage, as well as performance.
That's a nice addition! It's a "Goldilocks challenge" to have good turbulence for atomization, but not so much turbulence that the flow into the cylinder is compromised.
David Vizard would be proud. nicely explained & these efforts are much appreciated.
My 283 has a 3 angle valve job ❤
That makes me wonder if the OEM “tumble” helps atomization in a stock application where they are more concerned with emissions than performance.
What makes for good performance with valves usually makes for good fuel economy too. It’s just cheaper to machine oem stuff the way they do
Well said. The tumble and atomization create a good mixture that achieves a faster burn rate (good for performance & efficiency). The biggest factor for us, as a supercharged engine, is getting maximum flow rate through the valves.
This is good stuff right here
Thank you a ton
I like this! Is there more were this came from?
Thanks for the encouragement! We have a few ideas for the next set of videos... Been working on our motorcycle lately.
Not to much back cut on exaust valve, it can cause inversion.
Interesting, I have always done the seat, doing the face can be very tricky
Agreed. To be more specific, the *seats* may have 3+ angles, but valve face is usually 2 angles, one being the angle of the valve face contact area, and the second being the backcut angle up to the stem. There's some good pictures and data at johnmaherracing.com/tech-talk/3-angle-valve-job/
How about an interferance angle. 1 degree difference between valve sealing seat and seat? Get a better seal.
Interesting idea! This sounds like it would reduce the concentric contact area between the valve and seat. That contact area is a critical thermal path, especially for the exhaust valve, so the valve could run hot. It may be pounded into submission to match the angle of the seat over time.
😮
What happened to this channel? It disappeared and it would of taken off
We are still here! Been developing the race bike lately, working on some new videos soon. Appreciate the interest for more 👍