Valve seat angle width

General engine tech -- Drag Racing to Circle Track

Moderator: Team

65hardtop
New Member
New Member
Posts: 22
Joined: Sun Aug 02, 2009 7:55 pm
Location: Michigan

Valve seat angle width

Postby 65hardtop » Sat Aug 26, 2017 8:00 am

Im working on NHRA stock eliminator heads (newbie) and wondered what makes you decide on the width of a valve angle cut in the seat. I understand if I have a 45 degree seat that the wider it is the longer the valve job should last, in theory. But what about the other angles? Especially if you do a 5 angle job. And what what about a ground angle on the back of a valve? How wide should they be? I know someone who is stuck on one seat profile for some reason and won't try anything else.

Walter R. Malik
Guru
Guru
Posts: 3295
Joined: Tue Jul 24, 2012 10:15 am
Location: Roseville, Michigan (just north of Detroit)
Contact:

Re: Valve seat angle width

Postby Walter R. Malik » Sat Aug 26, 2017 9:34 am

65hardtop wrote:Im working on NHRA stock eliminator heads (newbie) and wondered what makes you decide on the width of a valve angle cut in the seat. I understand if I have a 45 degree seat that the wider it is the longer the valve job should last, in theory. But what about the other angles? Especially if you do a 5 angle job. And what what about a ground angle on the back of a valve? How wide should they be? I know someone who is stuck on one seat profile for some reason and won't try anything else.


With a "stocker" engine the valve job flow characteristics has to compliment the camshaft profile with the limited valve lift and visa-versa.
http://www.rmcompetition.com
Specialty engine building at its finest.

Smoke ring
New Member
New Member
Posts: 21
Joined: Sat Jul 15, 2017 1:21 am

Re: Valve seat angle width

Postby Smoke ring » Sat Aug 26, 2017 10:32 am

I'd get a spare head and do your own testing to find what's best for the lift area it's going to use. There's factors that come into play besides the angles. Valve margin is one, how far you sink the valve in the head is another, valve shape, top cuts, back cuts, etc.

ProPower engines
Guru
Guru
Posts: 6780
Joined: Sun Jan 21, 2007 1:16 pm
Location: VICTORIA BC CANADA

Re: Valve seat angle width

Postby ProPower engines » Sun Aug 27, 2017 1:07 am

65hardtop wrote:Im working on NHRA stock eliminator heads (newbie) and wondered what makes you decide on the width of a valve angle cut in the seat. I understand if I have a 45 degree seat that the wider it is the longer the valve job should last, in theory. But what about the other angles? Especially if you do a 5 angle job. And what what about a ground angle on the back of a valve? How wide should they be? I know someone who is stuck on one seat profile for some reason and won't try anything else.

As mentioned. The valve job must compliment the cam and port flow ability.
Not all heads respond the the same valve job so testing must be done to compare what valve job works best with the intake and head being run.

Some guys get hung up on port flow only while in limited applications the intake should be included in the equation to be sure what the engine see's is real world.
You may have an intake the flows well but bolted to a head with a bad valve job it can ruin the potential flow.

dare I ask what engine is being worked with?
Real Race Cars Don't Have Doors

65hardtop
New Member
New Member
Posts: 22
Joined: Sun Aug 02, 2009 7:55 pm
Location: Michigan

Re: Valve seat angle width

Postby 65hardtop » Sun Aug 27, 2017 1:32 pm

I'm working with a 73 mopar 340. So it's the lower compression combination.

Walter R. Malik
Guru
Guru
Posts: 3295
Joined: Tue Jul 24, 2012 10:15 am
Location: Roseville, Michigan (just north of Detroit)
Contact:

Re: Valve seat angle width

Postby Walter R. Malik » Sun Aug 27, 2017 4:10 pm

65hardtop wrote:I'm working with a 73 mopar 340. So it's the lower compression combination.


Do whatever you can to get the guide-boss out of the way and further test with a flat valve using clay on the backside for many shape angles to finally get where you want ... then have valves made that way.
http://www.rmcompetition.com
Specialty engine building at its finest.

mag2555
Guru
Guru
Posts: 1904
Joined: Sun Sep 18, 2011 10:31 am

Re: Valve seat angle width

Postby mag2555 » Mon Aug 28, 2017 5:17 am

While any added port flow will help those limited 340 heads, its a properly tuned Exh that yanks in needed Intake flow to make higher VE numbers on these motors.
The scavenging on these top running motors is so high that the jetting needs are boardering on crazy!

65hardtop, do you have a flow bench at your disposal?

You need to test many sets of heads to find a set that possesses the best average flow across all 16 ports to be the one to spend time working with ,and man this adds up to a lot of flow bench time!

Sometimes taking port dimension measurements will get you familiar with a castings core shift issues and with enough experience you can some what gauge how well a head will flow .
I find on a lot of castings from any manufacturer that due to the sand cast forms and the way the iron is poured in that one of the out side/ end ports will always have the most core shift or be the smallest CC wise and that port will always flow the least.
Good luck on your indevour!

Ron E
Guru
Guru
Posts: 2000
Joined: Wed Aug 03, 2005 8:35 pm
Location: nc

Re: Valve seat angle width

Postby Ron E » Mon Aug 28, 2017 8:52 am

Check the rules for newer replacement castings. They have improved exhaust ports. The car will like it.

Walter R. Malik
Guru
Guru
Posts: 3295
Joined: Tue Jul 24, 2012 10:15 am
Location: Roseville, Michigan (just north of Detroit)
Contact:

Re: Valve seat angle width

Postby Walter R. Malik » Mon Aug 28, 2017 10:20 am

Everyone outside of those actually running that type engine seem to think this "stock" stuff is simple.

Far from it ...
http://www.rmcompetition.com
Specialty engine building at its finest.

cgarb
Guru
Guru
Posts: 1269
Joined: Wed Jul 09, 2014 10:50 am
Location: Maryland

Re: Valve seat angle width

Postby cgarb » Mon Aug 28, 2017 11:33 am

Yes, one of our local engine shops the owners race in stock and superstock. I see some of their parts and they are anything but stock. The 351C heads with 3/4 inch of braze in the bottoms of the ports and the other is a 305 SBC that turns 8k on heads up runs. Not many Malibu wagons would do that from the dealership.

statsystems
Expert
Expert
Posts: 978
Joined: Sun Apr 03, 2016 12:17 am

Re: Valve seat angle width

Postby statsystems » Mon Aug 28, 2017 1:41 pm

65hardtop wrote:I'm working with a 73 mopar 340. So it's the lower compression combination.



Nail head or tulip valves?

I've never found a 45* valve job for that port that likes more than a .040 wide seat. If you kill a narrow seat it's because you have other valve train issues.

I've also never found a 45* valve job for that head that like 3 narrow cuts under the seat. The best I've found is a .060 wide cut under the 45 and the bottom cut needed to be over .100 wide.

If you are running a nail head valve you should probably stay with a 45. If you can run a tulip valve, you can look at some 50* valve jobs, even with limited lift. I don't buy the limited lift deal requires a 45* seat. The air speed through that port is very high. If you can get a 50* seat and a tulip valve you may have something.

I was told you can use other than 45* seats in Stock Eliminator so I'm basing what I posted on that.

I agree with getting more than a couple of spare heads and doing some thorough testing.

As I think about it...if it's legal I'd do a 50* seat on the exhaust if it's legal.

65hardtop
New Member
New Member
Posts: 22
Joined: Sun Aug 02, 2009 7:55 pm
Location: Michigan

Re: Valve seat angle width

Postby 65hardtop » Fri Sep 08, 2017 8:43 pm

We are in the middle of getting a different flowbench. Thought we had a superflow but it sold before we could get it. Looking at possible going the performance trends rout and building one. Our last one was homemade and worked great until just recently.
Nail head valves in these heads.

mag2555
Guru
Guru
Posts: 1904
Joined: Sun Sep 18, 2011 10:31 am

Re: Valve seat angle width

Postby mag2555 » Sat Sep 09, 2017 5:43 am

With the some what low short turn height in these Heads running a Tulip intake valve which may show a flow gain on the bench and the use of the typical fasting opening Cam as these motors usually run will totally counter act each other, a Nail head valve is the way to go and it needs to hang on the seat with the main seat being only 045" wide.
A cutter that will give a 15' 30' 45 should be used and then a seperate 60 degree cutter to bring the 45 seat down to .045" wide.
The 30 degree does not have to be that wide, only like .030" and the 15 degree only .020", it's the 60 degree that should be as wide as the rules and the head will allow you to get!
No radius valve jobs here even though they may show a slight flow gain on the bench.

The valve itself should be back cut with a 28 to a 32 degree and the width of this cut is what has a large effect on forming a Venturi at low lifts so plan on going thru a few of these valves to find the optimum width.
The margin must be no less then .080"
Exh flow wise heads like these with the chamber walls well backed away from the valve bowl on one side will need a very radiused seat arrangement since they don't use the chamber walls to start to guide the Exh flow towards the valve.

On the Head castings that only have short turn that is less then 75% as wide as it should be you need to focus on maxing out the low lift flow in regards to the valve job.

Ron E
Guru
Guru
Posts: 2000
Joined: Wed Aug 03, 2005 8:35 pm
Location: nc

Re: Valve seat angle width

Postby Ron E » Sat Sep 09, 2017 7:10 am

On the vintage heads, you'll have to watch the runner CC's carefully. I'm not sure if NHRA ever updated their specs. But, it was a common problem years ago that some of these heads would measure big on the intake side. Going to the better nail head valve will make the problem worse. I don't know how the later heads measure. Hopefully, they don't have the same issues as they come with nail heads.


Return to “Engine Tech”

Who is online

Users browsing this forum: bigblockmopar, Bing [Bot], Carnut1, Google [Bot], grandsport51, hip6, jcisworthy, KnightEngines, oldjohnno, sprint40, Truckedup and 26 guests