Valve seat angles

[GHP]

Ok, when is necessary to go to 50 deg or 52 deg valve seat angle?? The guy that done my heads last time had 50 deg seats with steel valves,
am using Del West Ti valves this time and they are 45 deg, am i going backwards going back to the 45 deg seats ? Pros and cons ?? heads are GM LS7, 0.740" lift lashed on the intake. Thanks in advance.

Regards, Garry

[In-Tech]

Higher valve lift(numerically) likes higher(numerically) valve angles and is RPM dependent. There are many many threads on this argument all over the internet.

The bottom line... there is no magic valve/seat angle nor lift nor overlap nor anything as a standard without more information of what you are trying to achieve. Do you think a large low rpm diesel would like a 60 degree angle?

Heat vs time is another. Time vs area of "seat" vs material of seat vs material of valve, etc etc etc.

Oh, and "cooling" of each vs overlap? Supercharged and turbocharged differ as much as NA. Limited apps that are in vacuum at WOT is a whole 'nother thing regarding overlap and control of "leftover" heat.

Anyhoosit, have fun.

[statsystems]

I run 50* seats on my street car with a .600 lift SFT cam.

I base my decision on several things. Is it worth the effort to make it steeper? Are you buying a custom cam to take advantage if steeper seat angles? Do you need the port area? I've never found a 45* seat that made better power over 88%, so if the bowl is over that, I use a steeper seat. And 88% is pushing it. The last question I ask is do you want the most out of it for what you are doing, or does it not matter if you leave a bit on the table?


I've been using steeper seats since about 1999. There are many aftermarket heads that come with a 45* seat and the bowl is past 90* (I suspect it adds runner volume and makes the "numbers" look better) and all those ended up with a steeper seat.

[CGT]

Ok, when is necessary to go to 50 deg or 52 deg valve seat angle?? The guy that done my heads last time had 50 deg seats with steel valves,
am using Del West Ti valves this time and they are 45 deg, am i going backwards going back to the 45 deg seats ? Pros and cons ?? heads are GM LS7, 0.740" lift lashed on the intake. Thanks in advance.

Regards, Garry

2.200 Valve?

[GHP]

Yes 2.2" valve it is.

[induction apprentice]

I would be suspect you can't lift the valve high enough on that head to where a 50 deg seat will be beneficial as that head without very good development will be turbulent hurting flow up their anyways. If you try correcting it laying the SSR back to much. You will hit water long before you manage the issue. So I would suggest you take the better reliability associated with the 45 deg seat and run it. The throats on those if I remember right are right around 88.5% as is. The curtain area will not get to far away from the existing throat area with the lifts that head will shine at. A little larger entrance leaving some taper and narrowing of the guide area, laying back the SSR some will all be the right direction for a performance application imo.

[KnightEngines]

I've had case recently where I've been wrestling with instability at high lift with a port & 45 deg seats, the application was borderline on needing 50 deg seats anyway, so I cut them (35/45/50/65/75) & sunk them a little to get a good top cut. I reworked the bowls & turns to suit the new valve job, but grinding was minimal.
Stability issues fixed & no loss of flow anywhere above .200" lift (which was suprising) plus a handy 15 cfm gain at the lift the motor will see (from 325cfm to 340cfm). Below .200" lift it lost a couple of cfm, which does not matter at all.

All the doom & gloom about loosing flow at lower lift is a little overstated, a 50 deg seat rarely looses meaningfull flow at any lift point that matters (unless you're running a hyd flat tappet with .450" lift).

[induction apprentice]

I agree any low lift losses from a 50 deg. Seat are not a problem in most cases. If a 50 deg. Seat could fix the flow instability on a factory LS7 casting. Then I would have to look at that as an option. But so far. I have not found that to be a cure with this head. The combination of valve to chamber wall shrouding/ no cant. As well as the aggressive ssr with the valve rolled ovef so much seems to really agrivate things much above .650"
I have not played with an RHS ls7 head yet. They have a raised runner that might help?

[user-9274568]

Ok, when is necessary to go to 50 deg or 52 deg valve seat angle?? The guy that done my heads last time had 50 deg seats with steel valves,
am using Del West Ti valves this time and they are 45 deg, am i going backwards going back to the 45 deg seats ? Pros and cons ?? heads are GM LS7, 0.740" lift lashed on the intake. Thanks in advance.

Regards, Garry

What is the top cut on that 50 seat? That is the key IMO.

[randy331]

I would use 30* seats on almost every application.

Need all the controversial low lift flow you can get.

Randy

[gmrocket]

You can't go wrong with 30/42/52/62/70

The bright bulbs on the tree will know why.

[CGT]

I would use 30* seats on almost every application.

Need all the controversial low lift flow you can get.

Randy

Low lift flow = Low end torque right? Do you also use a 15 degree back cut?

[statsystems]

I would use 30* seats on almost every application.

Need all the controversial low lift flow you can get.

Randy

Dammit Randy....you poking the bear this early in the morning?????

You know this will start a pissing match.

I love it. Thank you. Should make the day go better!!!!!

[Frankshaft]

Just regrind the valves to a 50 degree seat. If they aren't coated. If not, ti valves usually have super thick margins and there is plenty of material to work with.

[GHP]

That’s the problem they are coated DW Ti valves.
The engine is 440 ci Dart Next, single Dominator on a CID
manifold, 14.1 on ROO 16 made 815 hp on dyno, going to turn it up some more hence the Ti valves, unfortunately they have a 45 deg angle, my steel valves were 50 deg
just concerned about losing hp now. New cam has .763” minus lash, old cam .730” gross, guess I’ll have to see what the dyno says.