50 degree valve seats in modern hot street builds: is it finally time?
Posted: Fri Jun 01, 2018 6:47 pm
I'm a newb, it says it right in my forum name. But I can't help but see the results from a few of Randy & Rick's builds and EMC entries that are using 50-degree valve seats and seeing decent gains in average torque and power at very typical modern "street" valve lifts and RPMs and wonder: why not?!?
Most of these threads on this subject have been SUPER technical and I've tried to hang with them and absorb what I could but I'd love to see some lessons learned boiled down to some simpler and more salient points for any other Newbs/dummies like me.
My dumb newb conclusion is that it kinda looks like modern fast-ramp cams and supporting spring technology, and top-tier head designs mean that you can get a valve at higher lifts, for longer than you previously could and there ARE average power advantages that can be had EVEN at hot street valve lifts and RPMS...
Question: At what point do 50 degree valve angle's performance benefits start to make sense? I'm looking for an answer within the modern context of today's top-brand 23 degree SBC heads, & fast ramp -high lift street cams.
-I read somewhere that an old rule-of-thumb was that you don't see real gains on a 50 degree valve seat angle vs. a 45 degree valve seat angle until you get to an 0.25 lift to valve diameter L/D ratio (0.505" lift with a 2.02" valve diameter), but looking at a few real-lift examples, it seems that the benefits start FAR before that point (0.364" of valve lift with a 2.02" valve??)...
Example #1: http://www.hotrod.com/articles/1203phr- ... valve-job/ 1.94" diameter valve; Vortec head: Started showing airflow gains on the bench @ 0.350. That's gains starting at an L/D of 0.18. ->Does that mean that a typical 2.02" valve would start to see gains at that same L/D ratio? (0.364" and up?) On the dyno the engine saw the same or better torque across the whole curve from 3,500 - 6,500; an average gain of +12 ft lbs and a peak gain of 22 ft lbs @ the torque peak RPM. -Again this is with a super streetable, off-the-shelf Comp Cam (unknown #) with a max lift of 0.522 -VERY normal street stuff.
Example #2: The 2017 EM Traditional Muscle category winner from the Creason team. (Of course I'm using that example.) Ported Profiler heads, 2.02" /1.6" valve combo 238/244 @0.050 cam, 0.595" lift at the valve. (not sure on the seat-to-seat or advertised duration, but I'm betting it's pretty tight for the @ 0.050" #'s given the 1.8 / 1.85 rockers) -Yes it's an Engine Master's engine and yes the valve train is exotic but a 238/244 @ 0.050" diameter and 0.595" lift at the valve and the seat durations I bet are very reasonable for a modern, fast ramp roller cam. The hp peak @ 6,500. The whole thing (if it were on a roller cam with more reasonable 1.6 rockers) is very typical street stuff and I'm assuming it's benefiting similarly from the 50 degree seat angles or they wouldn't have gone with it in the first place. Randy talks up 50 degree seat angles in quite a few of his builds on here; most of them with bigger lifts and more RPM than this, though...
-It seems like the benefits of going with a 50 degree valve seat angle are very much applicable to modern street motor valve lifts and RPMs, no? Do the fast ramp speed cams and higher ratio rocker that help get the valve open quickly and into the "good air" (now even better air with the 50 degree seat angles) and to keep the valve in the good air for more degrees of duration, make up for the loss in low lift flow? (seems like it)
-Are there valve/seat / spring technologies that can help with longevity with a 50 degree valve seat angle? I'd think that a cam with a slower close ramp that could set the valve down nice and easy (isn't this the purpose of a "dual profile" cam-intake open agressively fast, but decelerate on the close ramp and avoid the "sewing machine" closes), and beehive or conical springs that are "just enough" pressure for the application could still go a good number of miles before you'd need to replace the valves.... -Yes / No? -Estimates on longevity?
Anyone have a before / after 45 degree / 50 degree dyno chart that goes a bit lower in RPMs? -I'm curious what the before and after torque looks like down at highway cruise RPM and a 50 degree seat would impact highway cruise MPG. A decrease in reversion during overlap from 50 degree valve angles should help MPG, right? (If torque is up and reversion is down then that should be an MPG @ cruise RPM benefit for 50 degree seat angles, too...)
Summary of my thoughts: The benefits of a 50 degree seat angle seem to be far more applicable to a modern street build than the old "only at high rpms and only beneficial over 0.550" valve lift" arguments; and if it's possible to still go 60,000 miles between top-end rebuilds with an appropriate cam and valve train, shouldn't more people go this direction?
More average torque, more peak RPM and still many, many YEARS between rebuilds for weekend-driven or summer-driven street cars sounds wonderful to me...
Adam
Most of these threads on this subject have been SUPER technical and I've tried to hang with them and absorb what I could but I'd love to see some lessons learned boiled down to some simpler and more salient points for any other Newbs/dummies like me.
My dumb newb conclusion is that it kinda looks like modern fast-ramp cams and supporting spring technology, and top-tier head designs mean that you can get a valve at higher lifts, for longer than you previously could and there ARE average power advantages that can be had EVEN at hot street valve lifts and RPMS...
Question: At what point do 50 degree valve angle's performance benefits start to make sense? I'm looking for an answer within the modern context of today's top-brand 23 degree SBC heads, & fast ramp -high lift street cams.
-I read somewhere that an old rule-of-thumb was that you don't see real gains on a 50 degree valve seat angle vs. a 45 degree valve seat angle until you get to an 0.25 lift to valve diameter L/D ratio (0.505" lift with a 2.02" valve diameter), but looking at a few real-lift examples, it seems that the benefits start FAR before that point (0.364" of valve lift with a 2.02" valve??)...
Example #1: http://www.hotrod.com/articles/1203phr- ... valve-job/ 1.94" diameter valve; Vortec head: Started showing airflow gains on the bench @ 0.350. That's gains starting at an L/D of 0.18. ->Does that mean that a typical 2.02" valve would start to see gains at that same L/D ratio? (0.364" and up?) On the dyno the engine saw the same or better torque across the whole curve from 3,500 - 6,500; an average gain of +12 ft lbs and a peak gain of 22 ft lbs @ the torque peak RPM. -Again this is with a super streetable, off-the-shelf Comp Cam (unknown #) with a max lift of 0.522 -VERY normal street stuff.
Example #2: The 2017 EM Traditional Muscle category winner from the Creason team. (Of course I'm using that example.) Ported Profiler heads, 2.02" /1.6" valve combo 238/244 @0.050 cam, 0.595" lift at the valve. (not sure on the seat-to-seat or advertised duration, but I'm betting it's pretty tight for the @ 0.050" #'s given the 1.8 / 1.85 rockers) -Yes it's an Engine Master's engine and yes the valve train is exotic but a 238/244 @ 0.050" diameter and 0.595" lift at the valve and the seat durations I bet are very reasonable for a modern, fast ramp roller cam. The hp peak @ 6,500. The whole thing (if it were on a roller cam with more reasonable 1.6 rockers) is very typical street stuff and I'm assuming it's benefiting similarly from the 50 degree seat angles or they wouldn't have gone with it in the first place. Randy talks up 50 degree seat angles in quite a few of his builds on here; most of them with bigger lifts and more RPM than this, though...
-It seems like the benefits of going with a 50 degree valve seat angle are very much applicable to modern street motor valve lifts and RPMs, no? Do the fast ramp speed cams and higher ratio rocker that help get the valve open quickly and into the "good air" (now even better air with the 50 degree seat angles) and to keep the valve in the good air for more degrees of duration, make up for the loss in low lift flow? (seems like it)
-Are there valve/seat / spring technologies that can help with longevity with a 50 degree valve seat angle? I'd think that a cam with a slower close ramp that could set the valve down nice and easy (isn't this the purpose of a "dual profile" cam-intake open agressively fast, but decelerate on the close ramp and avoid the "sewing machine" closes), and beehive or conical springs that are "just enough" pressure for the application could still go a good number of miles before you'd need to replace the valves.... -Yes / No? -Estimates on longevity?
Anyone have a before / after 45 degree / 50 degree dyno chart that goes a bit lower in RPMs? -I'm curious what the before and after torque looks like down at highway cruise RPM and a 50 degree seat would impact highway cruise MPG. A decrease in reversion during overlap from 50 degree valve angles should help MPG, right? (If torque is up and reversion is down then that should be an MPG @ cruise RPM benefit for 50 degree seat angles, too...)
Summary of my thoughts: The benefits of a 50 degree seat angle seem to be far more applicable to a modern street build than the old "only at high rpms and only beneficial over 0.550" valve lift" arguments; and if it's possible to still go 60,000 miles between top-end rebuilds with an appropriate cam and valve train, shouldn't more people go this direction?
More average torque, more peak RPM and still many, many YEARS between rebuilds for weekend-driven or summer-driven street cars sounds wonderful to me...
Adam