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valve seat VS dyno output
2

valve seat VS dyno output

valve seat VS dyno output

(OP)
I would like to know if any one has done any dyno testing W/differant seat angles.I have done testing on the flow bench(SF600)W/30* 45*50*and 55*seat angles.I have found the 30*to pick up low lift as would be expected and 50~55 to hurt low lift up to about .500 lift on the intake and not hurt the exhaust side as much.At any lift over .500 W/the 50* seat the port takes off like 40cfm in .100 of valve lift and you normaly see about 20~25 cfm W/45* stuff.Now I would like to know does the dyno show what you think it would ?45* stuff makes TQ lower than the 50*?(most of the NASCAR and prostock cars have the 50~55*stuff)Is the 50* to help wet flow into the bore?Help W/the reverse flow in the intake port?

RE: valve seat VS dyno output

2
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



Larry Meaux (maxracesoftware@yahoo.com)
Meaux Racing Heads - MaxRace Software
ET_Analyst for DragRacers
Support Israel - Genesis 12:3

RE: valve seat VS dyno output

(OP)
Thank you Larry Meaux for your Input on this.I have used set nascar heads that are going to go on my drag car.I asked the question about the valve seats because Low lift flow is week on the heads (301cfm @ .500 but jump to 345cfm @.600 and peek flow at .800 385cfm) Most of the stuff I have messed W/on the flow bench(aftermarket Big port heads)have much better flow at the .300~.500#s.Will that poor low lift flow = poor low end TQ?Would a change to a 15*30*38*45*65* seat and a 45*30*valve make the motor run down the track better?(the heads I am talking about are W8 mopar heads done by arrington)I do not want to make junk out of them or have a slow car LOL.thank you again Brett Miller.

RE: valve seat VS dyno output

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 emperical 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
----------------------------------------------------------
Would a change to a 15*30*38*45*65* seat and a 45*30*valve make the motor run down the track better?

the 15 and 30 is no good ..need to continue and blend the 38 deg into chamber is better

the 65 is not good enough for 45 seat

i can't reveal more , sorry !
------------------------------------------------------

and most of all ...air doesn't know where intake manifold port stops and head port begins

That killer head you are spending all your time on...what about the intake manifold/carb

What will they do to flow numbers ?

don't forget the most important aspect =>Flow test with complete intake and exhaust system attached to cylinder heads .  Don't flow intake manifold WITHOUT making dead sure other open ports on other side of intake manifold
are SEALED closed and that all ports in Heads have valves in them and they are also sealed by light springs

(need carb attached)
you are trying to make the air take the same PATH in your flowtesting as a live engine ..you DON'T want the other side of the intake manifold open like in some dumb magazine article tests i've seen.

you could go a step further and suck out of oil pan simulating flow robbing effects of intake manifold
even do this with valvetrain/camshaft /degree wheel
in a modified / dedicated block setup for this
need the SF-ProBench or better to accomplish this correctly


Larry Meaux (maxracesoftware@yahoo.com)
Meaux Racing Heads - MaxRace Software
ET_Analyst for DragRacers
Support Israel - Genesis 12:3

RE: valve seat VS dyno output

Will that poor low lift flow = poor low end TQ?

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

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

Larry Meaux (maxracesoftware@yahoo.com)
Meaux Racing Heads - MaxRace Software
ET_Analyst for DragRacers
Support Israel - Genesis 12:3

RE: valve seat VS dyno output

and here's a little more info about this subject
from a previous Post ;

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

Larry Meaux (maxracesoftware@yahoo.com)
Meaux Racing Heads - MaxRace Software
ET_Analyst for DragRacers
Support Israel - Genesis 12:3

RE: valve seat VS dyno output

(OP)
I aprceate you  sharing what I know is alot of TIME and trial and error.This will give me alot to look at and to do some more testing. Thank you for your Time and Information.Brett miller

RE: valve seat VS dyno output

(OP)
i could not get the pics to show up but link should work.The pictures are of the W5 heads that are on my motor now I ported them 2years ago and Had 45* 30* /radius cut into chamber.I found one strange thing the port did not like any back cut on the valve hut flow every time we tried a back cut  so they just have a 45* on the valve.BTW nice job On the head looks like some killer work. thanks Brett Miller.http://mediaservice.photoisland.com/auction/Jan/2004125...

RE: valve seat VS dyno output

Brett , i forgot to mention the Red lap-line is the 45 seat in that pic

on your W5 head, the intake seat insert looks like its
almost above the chamber floor ??  it might just be the pic angle...but if it is, you are probably going to get flow separation in that area from too much of an abrupt change in angle / transition from bowl to chamber

sometimes its better to actually "sink" the seat somewhat to get enough top angle transition into the chamber
when its done correctly you should have a flow increase almost everywhere in the Lift curve



Larry Meaux (maxracesoftware@yahoo.com)
Meaux Racing Heads - MaxRace Software
ET_Analyst for DragRacers
Support Israel - Genesis 12:3

RE: valve seat VS dyno output

Larry;

Any chance of you posting some complete pics of the chamber.

I understand if you can't. Just curious!

RE: valve seat VS dyno output

Willeng,

try http://www.maxracesoftware.com/

look in Photo Gallery = plenty pics , much more on the way

also MPEG dyno tests , but be patient with hi speed modem still takes awhile to completely load

Larry Meaux (maxracesoftware@yahoo.com)
Meaux Racing Heads - MaxRace Software
ET_Analyst for DragRacers
Support Israel - Genesis 12:3

RE: valve seat VS dyno output

I have found this thread to fairly informative, but one question does spring to mind. How does valve included angle figure in relation to seat angle and lift?

Just curious
Bryan Carter

RE: valve seat VS dyno output

Retracnic ,

depends on factory valve head shape angle you start off with but a 30 deg backcut works 90 % percent of time
with a 45 deg seat angle

On Brett's W5 head not likeing the backcut => its a sure sign that the short turn is wrong.
If the short turn is wrong =>won't like a backcut, if its correct , it will love a backcut !

it likes the no-backcut valve because its using the valve to correct the short turn problem in this way => the flow is going "further" around the valve's head without the backcut fooling the head thinking it has a different short turn curve ( this effect should be more pronounced between .400 to .600 lift range without backcuts)

in this situation, it might even not matter if you ground
the 45 seat on the valve till you had no more margin,
in other words, its not going to be that margin sensitive
.400 lift and up because its using the no-backcut to fool the head's short turn
But this is dry-flow conditions , and can change with bolting on intake and carb, it will sometimes move this effect upwards .100 " higher than when it 1st shows up
and in wetflow , it can be different again

where as , if the short turn is correct, it will love the backcut and result in better flow everywhere in flow curve

Larry Meaux (maxracesoftware@yahoo.com)
Meaux Racing Heads - MaxRace Software
ET_Analyst for DragRacers
Support Israel - Genesis 12:3

RE: valve seat VS dyno output

Great thread.  We have a valve lift rule in the stock car class.  The lift is .400 at the valve.  We are running a SBC, with 305 small chamber heads and a standard 45 degree seat.  What are the drawbacks to running a 30 degree seat?  Sure picks up flow, but I was wondering about longevity, as the 30 degree may not center the valve very well when the valve closes.  Any thoughts?  D

RE: valve seat VS dyno output

yeah , the 45 is definetly going to seal better and last longer

Larry Meaux (maxracesoftware@yahoo.com)
Meaux Racing Heads - MaxRace Software
ET_Analyst for DragRacers
Support Israel - Genesis 12:3

RE: valve seat VS dyno output

Ducky150 ,

the 15 and 30 deg top angles work great with
NHRA stockers and what you are doing

but don't work with modern designed chambers in all out effort large valve heads ..you definetly need a better
transition to chamber as you go above .25 times valve diameter .

Larry Meaux (maxracesoftware@yahoo.com)
Meaux Racing Heads - MaxRace Software
ET_Analyst for DragRacers
Support Israel - Genesis 12:3

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