50 degree valve seats in modern hot street builds: is it finally time?

[swampbuggy]

Warpspeed....heres another question that i am very curious about.....do you guys find any change in the valve lash after 500 miles of racing ? If you do would you mind sharing that info. (IF) you are at liberty to ? Mark H.

[Rick360]

Yes, makes one think: "As steep and narrow as metallurgy will support for the race distance."

Why do you think a narrower seat is preferred?

Rick

[DrillDawg]

So, your a "new member" with 5 posts, but 1: you know who Larry is enough to call him by his first name, and 2: that he did a test like that and shared the results, what, like 8 years ago?

Is that a problem? I was always lurking but couldn't see any of the pictures without signing up..

No, its not a problem. You must be new. There is a bunch of that going on it seems, creating different names and accusations of hiding behind screennames to bash people. It just seemed odd, that someone new, knew that stuff, that's all. We are trying to make speedtalk great again. Sorry, wrong side of bed last night, after a crappy week

People trying to be TRAIL BOSS is the real problem and jumping on a new guy is why a lot of people don't post and just lurk.

[MadBill]

Yes, makes one think: "As steep and narrow as metallurgy will support for the race distance."

Why do you think a narrower seat is preferred?

Rick

Just that while the angle and width both contribute to contact pressure, a narrower seat works to mitigate the reduced curtain area of a steeper angle.

[Rick360]

Yes, makes one think: "As steep and narrow as metallurgy will support for the race distance."

Why do you think a narrower seat is preferred?

Rick

Just that while the angle and width both contribute to contact pressure, a narrower seat works to mitigate the reduced curtain area of a steeper angle.

Why "mitigate" one of the benefits of the steeper seats? High lift flow improvement is not the reason for steep seats helping HP. IMO the low lift (or very low lift) curtain area change is more responsible than any gains at high lift.

With shallower seat angles a wide seat can limit the throat diameter but with steep seats there is plenty of room to use wider seats and keep the throat big enough using small angle changes into the throat.

Rick

[modok]

The difference between 45 and 50 degree valve seat, is only.....some .005" different.
I don't believe the air would notice such a small change in itself, rather the overall profile of the seat must be different to get a real change in performance. I would think one could make a seat profile to use 45 degree valve and still perform almost the same.
IMO it' right up there with accounting for carbon build up, which also could be about .005"

[Bryan Maloney]

50 degree exhaust seats have been beneficial on higher HP street builds. On a Whipple supercharged Gen 3 Hemi with a 1.600 valve and .640 valve lift, we have seen as much as a 30 rwhp gain. On milder NA engines with sub .600 lift, there has been little HP gain with the 50 degree exhaust.
On the flow bench the 50 exhaust seat gives up a few cfm at .100 and .200, but from .350 lift on up it is up 7-8 cfm to a 45 degree seat.
The angles I use on a 50 exhaust are 43-50-57. I like to keep the delta between the facets on the exhaust VJ to less than 8 degrees.
The exhaust throat gets blended right to the 50 facet, seat width is .065-.070
Street durability has been fine, especially with the newer copper-infused powder metal seats.

On the intake side, I usually stay with a 45 degree seat as most street heads do not have enough material in the chamber for the 43-45 degree top angle to work in conjunction with a 50 degree intake seat. The L/D ratio is lower on the intake valve as well.

[digger]

if you look at test of 35, 45 & 50 seats in that article results are all over the place. granted i'm sure what was tested wasn't the optimal 35 seat nor the most optimal 45 seat etc etc nor optimal cam but i'm not sure it works how people think it does. unless you know what of the cylinder fill start ,middle or end that it helps it makes it hard to choose when to use it on a certain application. one size fits all has never been how it works

[MadBill]

...Why "mitigate" one of the benefits of the steeper seats? High lift flow improvement is not the reason for steep seats helping HP. IMO the low lift (or very low lift) curtain area change is more responsible than any gains at high lift....

There are a number of other considerations of course, but a steeper seat opens up curtain area at a lesser rate. For example with a 45°seat, for every 0.100" of valve lift, the flow path (right angle distance between valve and head seat surfaces) increases by 0.071". For a 60°seat it's 30% less at 0.050".

[hoffman900]

The difference between 45 and 50 degree valve seat, is only.....some .005" different.
I don't believe the air would notice such a small change in itself, rather the overall profile of the seat must be different to get a real change in performance. I would think one could make a seat profile to use 45 degree valve and still perform almost the same.
IMO it' right up there with accounting for carbon build up, which also could be about .005"

Don’t think of it as air, think of it as pressure. It’ll notice any and all changes in orfice size.

[Warp Speed]

...Why "mitigate" one of the benefits of the steeper seats? High lift flow improvement is not the reason for steep seats helping HP. IMO the low lift (or very low lift) curtain area change is more responsible than any gains at high lift....

There are a number of other considerations of course, but a steeper seat opens up curtain area at a lesser rate. For example with a 45°seat, for every 0.100" of valve lift, the flow path (right angle distance between valve and head seat surfaces) increases by 0.071". For a 60°seat it's 30% less at 0.050".

Kinda a have your cake and eat it too scenario when properly used!
When we first developed steeper seat angles for our deal, it was because of the gains in mid to high lift flow. Everything else became a pleasant by-product as things developed, with a better understanding of what was also effected.

[Warp Speed]

The difference between 45 and 50 degree valve seat, is only.....some .005" different.
I don't believe the air would notice such a small change in itself, rather the overall profile of the seat must be different to get a real change in performance. I would think one could make a seat profile to use 45 degree valve and still perform almost the same.
IMO it' right up there with accounting for carbon build up, which also could be about .005"

Don’t think of it as air, think of it as pressure. It’ll notice any and all changes in orfice size.

Yep

[hoffman900]

The difference between 45 and 50 degree valve seat, is only.....some .005" different.
I don't believe the air would notice such a small change in itself, rather the overall profile of the seat must be different to get a real change in performance. I would think one could make a seat profile to use 45 degree valve and still perform almost the same.
IMO it' right up there with accounting for carbon build up, which also could be about .005"

Don’t think of it as air, think of it as pressure. It’ll notice any and all changes in orfice size.

As an addendum...

Bret,

Here are some thoughts I've had for a very long time......
Engines work off of pressure differentials--ie, differential equations......
In unblown engines we have a positive pressure(back pressure) in the exhaust pipe, and a negative (vacuum) in the intake port BTDC. The piston is moving upwards, pushing the exhaust gases out the exhasut port. The numbers aren't far apart, say 1 1/2 lbs backpressure, a few inches of vacuum, but it does not allow flow into the combustion chamber. Then TDC, and the piston starts down. As it moves downward, it is creating a volume where no volume had existed---and atmospheric air pushes in to fill that volume. This is even why cars run better on cold days that in the heat of summer, the cold air weighs more, and fills the cylinder faster because of inertia.
I'll be a little scattered myself, because of the lateness of the hour, but two points of interest.
First---The engine never has long-term memory. It only knows what is happening NOW, and what just happened. Here is an example:
Intake opening 40* BTDC--- Is this a
288* cam on 104 ICL?
292* cam on 106 ICL?
296* cam on 108 ICL?
300* cam on 110 ICL?
304* cam on 112 ICL? or a
308* cam on 114 ICL?
With symmetrical cams, all those intake durations and ICLs open at 40* BTDC.
Or, if it is an unsymmetrical cam, it might be a 288* cam on 101 ICL, like in my UD 288/296R6.
At .200", the 288 is as fat as many 300* cams, but the upper part of the cam lobe is way advanced compared to them. The engine sees the overall shape of the cam lobe, not some number we use to measure it with. The higher the port velocity, the better the inertia ram.
Second---Most engine builders, probably you too, have tried the same cam lobes ground on different LSAs, say like 106 and 108. If you dyno them in the same engine, and on the same Intake CL, both cams obviously have the same intake cam on the same ICL. Oddly enough, they have different power curves, and everyone says "Sure, because of the different LSAs!". Remember, they both had the same intake lobe on the same intake CL. The power curves differed because the effects of the exhaust back pressure and the resulting reversion were different for each test, and each cam filled differently because of their reversions. Once you start thinking on this, it leads all sorts of interesting directions......
Enough for me tonight, see you all tomorrow.....

UDHarold

PRI is next week. I will be around very little.....

Jay,

The intake backflow covers up to .250" valve lift, but the way the reversion works is like this:
Still using our 40* BTDC valve opening point.
Think of the insides of the combustion chamber at 41* BTDC---The piston is moving as fast as it's going to for the next 41*, it is slowing down and must hit 0 velocity at TDC. The burned exhaust gases are being pushed out the cylinder/combustion chamber, they have an ever-decreasing volume and backpressure.
Now we get to 40* BTDC and the intake valve is about .001" off the seat. The pressure differential is such that some of that exhaust gas goes around the valve into the intake port. The initial disturbance is the greatest disturbance, the piston velocity is dropping, and so is the exhaust volume and backpressure. A port designed to minimize that flow into the intake port will help the port recover sooner after TDC, and make it start airflow earlier than one that does not minimize reverse airflow. As I said earlier, the best airflow, that sets up the port velocity for later inertia-ram flow, occurs in the .250" to .600"-.650" valve lift range.
But I am not a head porter, and these are just my thoughts, from the cam design side. This is what I think happens, and I've been thinking it for a number of years. It is all simple physics, and what happens must agree with simple physics.

I hope this gets you all thinking......

UDHarold

[swampbuggy]

Warpspeed, did you miss my question about post race valve lash numbers ?? Mark H.

[Frankshaft]

Is that a problem? I was always lurking but couldn't see any of the pictures without signing up..

No, its not a problem. You must be new. There is a bunch of that going on it seems, creating different names and accusations of hiding behind screennames to bash people. It just seemed odd, that someone new, knew that stuff, that's all. We are trying to make speedtalk great again. Sorry, wrong side of bed last night, after a crappy week

People trying to be TRAIL BOSS is the real problem and jumping on a new guy is why a lot of people don't post and just lurk.

I apologized to the guy. I shouldn't have said anything, but obviously I wasn't the only one with the same thought. And its Site Captain. I am definitely not trying to be the site captain here.