Valve seat angles. - what are people using?

[Greg]

I've read a bit about people using angles higher than 45* for their valve seats, up to 52* to improve high lift flow.

Has anyone tried this out? and what difference did it make?

I know some old stuf uses 30* seats for the same reason, it improves low lift flow but is 45* the optimum all round seat angle or is it just a nice number to start with?

one other thing, back cutting valves usually increases the flow numbers and I'm sure on an inlet it would make more power but even though it increases ex. flow, do you think it would increase reversion in the exhaust and therefore lose power?

[maxracesoftware]

with an all-out camshaft ,

Low-Lift flow increases "act" like you are increasing
the OVERLAP period and DURATION

so what happens at very low RPM , HP/Torque gets hurt
by increses in low-lift flow with all out cams

most times its BELOW the RPM range you are interested in
so it has no negative effect down low

Low-Lift flow usually picks up TopEnd ..not the very bottom end

Low-Lift Flow = similiar effect as INCREASING duration/overlap

the trouble is a valve is not a One-Way device
usually making low-lift flow increases also result in
increasing valve's ability for reversed flow

another example is the NHRA SuperStock Chrysler 318-340-360
engine .... before NHRA let any valve shape be used ,
the stock Chrysler intake valve was a Tulip-design,
it hurt low to mid-lift flow numbers , but high lift were OK

after NHRA allowed any valve shape , we went to a nail-head
design with backcut angles, low to mid-lift numbers
increased with high lift numbers the same as before with Tulips

on the dyno, the Tulips made torque sooner , come on the cam sooner,

with the nail-head valves, torque began later, but wound up as much
peak torque and with a little more Peak HP , but higher by 200 RPM

Actual DragStrip runs were faster with nail-head after rear gear ratio was increased
to compliment .....than was with Tulip valve head
-----------------------------------------------------------

Sort of what Bill Jenkins was trying to describe in his book
and also what Phillip H . Smith's
"Scientific Design of Intake and Exhaust Systems" =>where when the
intake flow was too good for low RPM airflow demands,
you lost too much ram effect at end of stroke.
You got it back as you reved the engine higher if cam timing was OK

30 deg angle= for cams up to .400 to .450 Lift applications, but 45 deg also works great in this range
if done correctly

45 deg angle = .400" lift and upwards

50 to 55 deg angle= high lift cams with large valves

but be careful, just because it flows more with 50-55 angles is not a dead certain fact it will show you more
HP / Torque or faster in actual LIVE runs or dyno

i have a 45 deg custom Serdi profile that will flow
2 to 3 PerCent less on the FlowBench than 50-55 deg , but on the dyno will be approx 10 average HP better thought the power curve and also runs down the track faster in actual LIVE runs

50-55 deg still is great, but a great 45 deg Profile is close also to matching performance in older style ports!

as short turn radius gets larger and entire port straighter
and higher with large valves go to 50-55 angle for mid to high lift flow and reduced flow reversion/over scavenging

very simple ballpark equations ;

30 deg angle= .300 " Lift

45 deg angle= .450 " Lift

50 deg angle= .500 " Lift

55 deg angle= .550 " Lift

See the imperical ballpark pattern ??

then ask yourself how much LIFT and how long is my cam
staying in those ranges during peak piston velocity point TILL peak cylinder volume depression rate point
(Hint=> between 70 deg ATDC till 120 deg or so)
Need a large diameter accurate degree wheel, 1 " inch .001
dial indicator/magnetic stand/plate/pointer
Time and patience or Cam Doctor printout

Example=>
then look at what lift you are at
if you are staying at or above .500" in that range, go with 50 deg seat

a very important point=> to get the valve out the way and let the ports do their thing ....
then ; (Ballpark recommendations=>)

Intake_Valve_Minimum_Lift = .37 * Intake_Valve_Dia

Intake_Valve_Max_Lift = .41 * Intake_Valve_Dia

Exhaust_Valve_Minimum = .45 * Exhaust_Valve_Dia

Exhaust_ValveMaximum = .52 * Exhaust_Valve_Dia

Curtain_Area = Valve_Area at .25 * Valve_Diameter

You camshaft lift SHOULD be determined by your valve diameters in all out racing ....then DURATION is just a matter of where in RPM range you want peak HP / Torque points

Peak_HP = Flow_CFM * .257 * Number_of_Cylinders

is estimated potential Peak HP to expect
you multiply .87 percent times cam's theoretical max lift , round off to nearest .050" in Flow Test, then see what CFM is at 28 inches

example=> .700" Lift cam
.700 Lift times .87 percent = .609" Lift
Flow head at .600" Lift , then take CFM at 28 inches and calculate HP potential with above formula

.257 Factor = for beginning engine builders and engines near 10.0:1 Comp Ratio

.285 Factor = would be for Professional engine builders with wet sump pans, lightweight rotating assemblies, low tension great sealing rings, deep oil pans, etc.
excellent use of inertia/wave tuning with 9.5 to 11.5:1 Comp Ratios or
11.5 to 13.0:1 CR ranges without fully utilizing inertia/wave tuning effects

.300 to .310 Factor = Current ProStock Technology with dry sump, unlimited carburetion, Hi Comp Ratio, ultra lightweight rotating assembly, etc, max use of inertia/wave tuning, etc, 14:1 to 17:1 Comp Ratios
(usually no better than .3200 efficiency or no worse than .2980 eff %)

all factors are just baselines

major errors will be from no 2 FlowBenches or Dynos read the same

and there are people with bogus FlowBenches and bogus Dynos out there ..that makes above Factors appear to be incorrect

but if dyno or flowbench is honest,
those Factors will be very close to reality

but its still bench racing
just gives you a ballpark guesstimate of what to expect.

[Greg]

Wow,
Thats a lot of stuff to digest but very interesting!
Ill try out some of your formulas etc to try and get my head around it but it does make sense and obviously your track times prove it.
If its not a rude question, what profile is the 45* serdi cutter you use? I see Goodson are selling some new profiles under Mondello's name which I might try as well. I was playing with Serdi's radiused/multi angle cutter the other day on a aftermarket holden 308 head and it actually lost around 5cfm from .400>up compared to a 15*/45*/70* straight 3 angle cutter. Both had .040" wide seats and the same ports. The radiused cutter makes a big difference to multivalve heads though which makes sense reading your stuff above as they only lift .400" or so but then using a lift/dia ratio its about the same as a 2.5" valve on a big v8.
OK, ive confused myself now... lol.. time to go do some more playing.

[maxracesoftware]

custom ground intake Serdi profile not in catalog nor available =
Intake
1st top cut = radius in Serdi profile..then blend into chamber
2nd=38 deg
3rd= 45 seat angle
4th=60 bottom
5th=75 bottom
6th= radius in Serdi profile..then hand blending into bowl area

Exhaust
full radius profile available in catalog

or
1st top=38
2nd=45 seat
3rd=60
4th=70
then hand blending 70 deg into 60 deg plus a little more blending of 60 deg into 53 deg

hand blending 38 deg top cut into chamber
==============================================

if you look closely, there are 6 angles on intake side along with hand-blending (full radius on exh side)


in this pic its harder to see the distinct angles because of a little hand blending into chamber and bowl-area


if its done correctly..it will run down the DragStrip as fast or faster sometimes than a 55 deg seat setup that Flows 3%+ PerCent more on a FlowBench

[SWB]

Larry,

How wide a seat do you use for your endurance engines and how does seat width affect valve sealing?

Greg,

I've been using a Newen-003 on most of my inlet seats and it's been working pretty well. Very similar profile to what I used before I started using seat cutters.

I've also tried the 5119, which is a 10mm radius off of the 45* seat and tangent to it. I was not real impressed with that cutter and I think the problem was that the radius starts at 45* instead of something steeper. This may be causing the air to flow as though the seat were much wider than it really is and that would explain the results I obtained.

Larry's exhaust profile sounds like it would work good to me, it's not far off what I've been doing, just a steeper top angle.

Sean

[Shawn]

I've seen alot of heads from a well known head porter.His exhaust seats have no seat angle cut in them. It's just one large radius with the "peek" of the radius being where the valve sits. The valves are lapped in and create a seat that looks almost like a penciled in line on them. These heads had copper seats in them and i would have sworn up and down that it would have burnt the valves, but it didn't.
Shawn

[maxracesoftware]

I've seen alot of heads from a well known head porter.His exhaust seats have no seat angle cut in them. It's just one large radius with the "peek" of the radius being where the valve sits. The valves are lapped in and create a seat that looks almost like a penciled in line on them
===================================================

i've seen the same type valve job you describe on a pair of SS Hemi heads
on both the Intake and Exhaust sides....looked like about a .010" Lap Line width at most

for DragRacing about .040" to .050" wide seat angle on head
for endurance / street = about .050" to .060" wide max

[maxracesoftware]

an old pair of rare angle-plug #492 castings (before#292 Turbo)
with .050" -.060" seat widths


.040"=Intake .050"=Exhaust

[bruce]

Larry,

If I may ask, what are you using to get the surface finish you get on the intake ports?

Wish I "worked" in the OHV world you have some excellent info on seat angles. I'm gonna have to use that info for my side valve port R&D work if and when I get some time to sit down and play at the flowbench, well make that "I will get" some time to do some R&D . . .

[maxracesoftware]

these Pics are all with 60 Grit
Standard Abrasives #709187 CR-ST 1/2 x 1 1/2 x 1/8 60-AO-RB
CR= Cartridge Roll 1/2 diameter by 1 1/2" inches long with 1/8 pilot hole
AO= Aluminum Oxide
RB= Resin Bond as glue
------------------------------------------------------------------
these pics are with varying degree of grinder pressure will produce different finishes with the same 60 Grit Roll =>






this Pic is all with 60 Grit Roll..varying pressure & time, especially in the Bowl, no WD-40 , just dry finish


this next Pic is with new 60 Grit Roll ...and about the "roughest" finish i use
and could be made to look finer by just wearing out the 60 Grit and changing grinder pressure and time spent


a little smoother, shinier finish with new 60 Grit, but this time with a light spray of WD-40 or LPS-2 , then finishing with 60 Grit

-----------------------------------------------------------------------

this last pic shows the a Finish difference using the very same 60 Grit Roll , but just varying the pressure and time =>



this Chamber finish is about the finest you can acheive with a 60 Grit.
Works better than using a 120 Grit, a worn out 60 Grit will look like a 120 Grit, but shine brighter side-by-side

as you can see, there is quite a bit difference in the look of the Finish between the intake bowl and the Chamber..yet its the same 60 Grit Roll used

every once in awhile i get a batch of 60 Grit rolls by accident that are awesome...they just cut and finish smoother, and keep these rolls only for final finish work
use a Makita electric die grinder (Plastic Blue Green color) $100.00 dollars with 10 or 15 amp constant torque speed controller
and vary your grinder pressure and time..and the 60 Grit roll will start to act like a 120 Grit roll but cut better and shine and finish better.
Hard to describe, but its sort of like "Spit-Shine" shoes..at first its hard to accomplish until you get the hang of it

[Shawn]

What do you use for your speed contoller?I have always used air tools, but have recently fiddled around with a bosch grinder that seems to work ok, but i need to slow it down a bit.I just hate it when it fires up and your 6" long bit goes a little out of balance and it bends that thing at the shank. Makes is tough to hold on to!
Shawn

[maxracesoftware]

Links to various Speed Controllers












i use Dayton 10 amp, but no longer available, the ones above might be better ?


you need the shank to run as smoothly as possible without vibration for a good finish .

[wrs]

maxrace, Thanks for all of the great information, I follow your posts on three different boards and read them several times over, awesome information.

I do a lot of work on turbocharged diesel engines. What is your opinion on port size and shape for a turboed engine vs. a na engine. These engines are in the 450-1500 hp depending on engine size and turbo size. My feeling is that the port is going to require a larger cross sectional with lower calculated velocities on the bench because on the engine the velocities will go through the roof.

Or maybe a good na port will be a good turbo port?

What is your opinion?

Thanks,
wrs

[maxracesoftware]

Thanks, wrs

if you look at a 8000 HP / 6250 TQ Nitro Top Fuel Engine
with a SuperCharger ...thats a lot of Power being made with a Fuel that because of its A/F Ratio -vs- gasoline takes up a lot more space in the cross-sectional area of the Intake Ports, yet with all that going on, the cross-sectional area is not as big as you think it would have to be , in HP-scaled up or relative size. Then you look at the Exhaust side and see the same thing, its also exhausting 8000 HP out of 1.940 or 2.000 exh valve and maybe a 2.500" OD pipe.

Naturally-aspirated engines rely on the correct cross-sectional size for the engine RPM range and CID size, to make their best VE, HP, and TQ, BSFC numbers

Any Blower or Turbo making 15 psi boost on upwards is going to dominate or overide the Intake side's sound wave and mixture inertia energies created by the cross-sectional area and lengths....and give you more leeway if you ported the intake port a little too large or too small up to a point.

You're not going to make 8000 HP thru a Soda Straw no matter how much Blower psi,..a certain size cross-sectional area is always needed for the application, but with a Blower its not as critical as Naturally-aspirated engines.

everything you do to findout the best Flowing port shape will still apply in Turbo/Blower applications , its just the cross-sectional areas and port lengths won't be as critical

Again, just study a TopFuel engine for ideas

[maxracesoftware]

the single biggest mistake i see Racers make with Blowers or Turbos is this =>

"They want you to port the exhaust side of the heads , and leave the intake sides alone, as they think they will just "Stuff it in" with the Blower"

They don't realize the Intake side porting is now 2 or 3 + times more important/critical than the Exhaust side with a Blower or Turbo

if i port a pair of heads that gain 50 HP Naturally -aspirated , those same Cyl Heads will now make double or 100 HP+ gains with 15+ psi Boost

if i would not have worked on the Intake sides, there would be "NO" 100 HP gain...and there is no way you are going to gain 100 HP working on the Exhaust sides

the Intake side is where its at....gains here will be more than double or triple or more depending on Boost psi,...and with much better flowing Intake ports you can make more HP/TQ with less Boost psi, resulting in a safer engine. Look at Top Fuel today with awesome Cylinder head porting design on Intake and exh sides ...you see a lot less engine explosions as now they make a ton of HP thru well designed ported heads compared to old days .

again, look at TopFuel engine exhaust port size and header pipe size needed to exhaust 8000 HP ...its not 10 times larger in size than a 800 HP engine !