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

[statsystems]

To be fair, Brodix is covering their butt because most have no idea what they’re cobbling together. The other what is “a lot”? Is 20k a lot? The GM LS engine are going to go over 100k miles. That seems more like a lot to me, but it’s all relative.

That's a fact. Brodix doesn't know who's on the other end of the phone. Covering their asses and I don't blame them.

[hysteric]

IMO, a steeper seat is always beneficial in some cases. Number one is when the port is too damn small for valve diameter. You see this on Chrysler's. The port is already too small for the valve and the lift curve falls over at higher lifts. You can't get all that out with the valve job, but you can help it.

Can please elaborate further on this?

Are you talking OEM heads and if so what size valves in which heads?

[GARY C]

SBC 350, 10.2:1 Static CR
Profiler 195cc heads (as cast); 2.01"/1.6" valves (PAC beehive springs * 10 deg steel retainers recommended by Mike Jones)
Cam: Mike Jones HR70375 -aggressive HR but not his noisy, REALLY aggressive lobes 227/228 @0.050 272/280 @0.006" .375"/.360" lobe lift (0.600"/0.576" with my 1.6RR)


Any guess what kind of increase I'd see if at next rebuild I moved to 50 degree seats?
How would you go about estimating such a thing?

(Danger: Newb making up not only #'s but calculations based upon nothing): Just roughly estimate +10 CFM at 0.500" - 0.600" lift? 273 CFM -> 283 CFM or a 3.7% increase; then take current ft lbs between 3,500 and 6,000 and multiply by 1.037 to end up with magical space math new torque estimates?!?

All baiting of the calculation nerds aside, I REALLY like super torquey street builds (I went with the strange aftermarket TPI-style "FIRST Fuel Injection" intake, the Profiler heads, a short-ish duration, high-ish lift cam, tri-y headers based build for that reason) and the idea of another 10-15 ft lbs everywhere in the curve and a bit of anti-reversion for going with a 50 degree seat angle valve, if I can still get 50,000 miles between rebuilds, sounds like the kind of trade-off I'd be happy to make.

-I see huge conflicts between typical advice on this subject, and the results from a couple of select builds so I have to stop and ask a few questions.
(I wish Chad Speier was still on here as a few of his posts (now a random deleted user acount #) seemed to indicate that he's given up on 50 degree valve angles almost entirely and I'd love to know why.)


Adam

Keep in mind that if your port work and cam are optimized for a 45* seat just switching to a 50* could loose power, you always run that risk when changing something on a combo.
I would focus on the one you are going to run.

You won't know unless you test it. How are you saying that an optimized port for 45* seats would lose power with a 50 unless you test it? The only way to test it is put in on a dyno and then take it to the track.

Not saying it will, saying it could.

[statsystems]

IMO, a steeper seat is always beneficial in some cases. Number one is when the port is too damn small for valve diameter. You see this on Chrysler's. The port is already too small for the valve and the lift curve falls over at higher lifts. You can't get all that out with the valve job, but you can help it.

Can please elaborate further on this?

Are you talking OEM heads and if so what size valves in which heads?

Yes OE stuff, but even some of the aftermarket stuff doesn't have the cross section for the valve size.

As an easy example, I'd rather run a 50* seat with a 2.02 valve than to use a 45 and a 2.05 or bigger valve.

One example comes to mind is the Chrysler stage 6 head. You can't make the port big enough and a bigger valve makes it worse.

[hysteric]

Thanks Stat.

I'm playing with small block stuff mainly 360 587 and 318 heads atm both 302/675 and the ports are really small to say the least and was wondering about which way to go with valve angles.

Might have to give the 50-55's a go and see what happens.

Thanks again.

Hysteric

[Carnut1]

I thought about this quite a bit for my Dart 215's which will be street heads. I want the durability and to stress test it at will so I decided to stay at 45 seat. Guys that love the steeper seats never really tell all I think. They say the 50 pulls harder on the port. Ok, is that throughout the lift curve? How do they quantify that? I can see by the geometry that the 50 will work better at higher lifts. The reversion arguement calls for a different cam. When going from 45 to 50 seats. Or does it? I could see having a fairly radical 45 seat setup then going to a 50 and the idle and low speed torque improve. Hell it may improve everywhere. Does that make it better or would the 45 degree setup be as good with some ar techniques or just a different cam? The big question I have been looking for is does the 50 satisfiy cylinder airflow demand better? If so how? It will be a long day here today so tear me up and I will get back when I can't sleep.Thanks, Charlie

[Warp Speed]

Yes, the time for 50* seats is here. Was here years ago.

The problem is guys who live and die by flow bench numbers look at a 50* valve job say it won't work in a street car because low lift is down, and you only get it back until high lift.

I consider that an abuse of a flow bench.

It almost seems you change your point of view depending on who's giving it?!?

Where did I say anything different? I've never said the flowbench was the end of everything.

I just did the same thing I call you and some others out for. I appologize!
This is a good discussion, carry on, and try to keep an open mind!
I will also!

[swampbuggy]

Dart Machinery has been putting steeper seat angles on their big block heads that flow a LOT, trying to get all the MAX. flow they can at higher lifts. I am quite sure that is their reason. Warpspeed....does NASCAR mandate any seat angle spec.'s ???? Mark H.

[Warp Speed]

Warpspeed....does NASCAR mandate any seat angle spec.'s ???? Mark H.

Not yet! Lol
It's pretty much self governed by acceptable seat wear.

[Walter R. Malik]

Warpspeed....does NASCAR mandate any seat angle spec.'s ???? Mark H.

Not yet! Lol
It's pretty much self governed by acceptable seat wear.

I have an older cup engine from the 90's that I recently pulled apart and am re-purposing. It has C3 "Yates" heads.
The intake seats are 50 degree but, the exhausts are 45 degree; these have ductile intake seats, copper beryllium exhaust seats and titanium valves.

[user-30563]

Would you still run a 50º seat if the 45º made the same power? I wouldn't...

I think that is what Chad was saying in that thread before everyone got out of control!

[RevTheory]

Would you still run a 50º seat if the 45º made the same power? I wouldn't...

I think that is what Chad was saying in that thread before everyone got out of control!

I know Chad was beginning to talk about how those seats pulled velocity on the port a little differently but he got steamrolled before he was able to elaborate.

That was an unfortunate loss because I think it would help you decide which way you want to go for a given application.

[user-30563]

Would you still run a 50º seat if the 45º made the same power? I wouldn't...

I think that is what Chad was saying in that thread before everyone got out of control!

I know Chad was beginning to talk about how those seats pulled velocity on the port a little differently but he got steamrolled before he was able to elaborate.

That was an unfortunate loss because I think it would help you decide which way you want to go for a given application.

I agree with that as well, but one needs to have some faith in velocity readings.

Another reason, IMO is just valves margins in general. Some valves like REV already have a thinner margin with a shelf style. The Manley and Ferrea exhaust margins are plenty thick so converting them to a 50º isn't a issue. About a .050 thick intake margin is about as thin as I would go..

Now, shallower angled heads, changes things... I feel you design a chamber, port for the seat angle.. And I also agree the top angle almost trumps the seat angle!

[RevTheory]

I dug up a thread from like 2007 awhile back and Darin Morgan was talking about top cuts and seat angles and his opinion was basically if you don't have enough meat in the chamber for a proper top cut for a 50* seat, don't do it!

[statsystems]

I also forgot to mention that as the seat angle goes up, the nail head valve is not as good. I won't use a nail hard valve and a 50* seat.