Valve Angle?
01-26-2006, 01:23 PM
#1
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Valve Angle? Tried searching but did not come up with much...
Looking to learn about vavle angle.
1.What and how does it effect what it does?
2.Is valve angle something you can change from one set of heads to another. For example can i use stock heads one day and the next install an aftermarket head with a different valve angle? If not why? what else is effected by the change in geometery.
3. What are the benefits and cons to changing valve angles?
Thanks!
Looking to learn about vavle angle.
1.What and how does it effect what it does?
2.Is valve angle something you can change from one set of heads to another. For example can i use stock heads one day and the next install an aftermarket head with a different valve angle? If not why? what else is effected by the change in geometery.
3. What are the benefits and cons to changing valve angles?
Thanks!
01-26-2006, 03:32 PM
#3
Valve angle is the angle the valvestem is on in relation to the cylinder bore. Our engines run a 15 degree angle, where as SBC engine are 23 degrees and nascar engine run 18. The new ls7 motor runs 12 degree heads from the factory. The lower angle means you can run a smaller combustion chamber before running into piston to valve colission issues. It also allows the air to enter from all sides of the valve when the air is being pulled down the bore by the piston. Imagine a valve at 45 degrees. The air would have to flow upward to enter the cylinder at the top part of the valve head. Also, larger valve angles will push the valvehead closer to the cylinder wall as the lift grown, creating valve shrouding issues.
You can mildly change valve angles by angle milling heads, however youll run into issues with intake fittment. ETP makes 11 deree heads, however i'm not sure if theyre intended for ls7 use only or not. I would imagine an aftermarket head casting could change the valve angle slightly before running into geometry problems requiring different rocker arms and pushrods.
You can mildly change valve angles by angle milling heads, however youll run into issues with intake fittment. ETP makes 11 deree heads, however i'm not sure if theyre intended for ls7 use only or not. I would imagine an aftermarket head casting could change the valve angle slightly before running into geometry problems requiring different rocker arms and pushrods.
01-26-2006, 07:12 PM
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Originally Posted by GuitsBoy
You can mildly change valve angles by angle milling heads, however youll run into issues with intake fittment. ETP makes 11 deree heads, however i'm not sure if theyre intended for ls7 use only or not. I would imagine an aftermarket head casting could change the valve angle slightly before running into geometry problems requiring different rocker arms and pushrods.
01-26-2006, 09:12 PM
#5
Ok one more thing....
Valve angle and port height (on the intake flange from the deck) should go together as well....
If you have a shallower valve angle and the same port height you have more issues with your short side radius and more problems with turbulence in the port. There is a relationship to valve angle and port height along with the short side radius.
You can do more things with a shallower valve angle if the rest of the port is built around it. This is one of the reasons the 18° low port SBC heads are worthless compared to the high port 18° heads.
Bret
Valve angle and port height (on the intake flange from the deck) should go together as well....
If you have a shallower valve angle and the same port height you have more issues with your short side radius and more problems with turbulence in the port. There is a relationship to valve angle and port height along with the short side radius.
You can do more things with a shallower valve angle if the rest of the port is built around it. This is one of the reasons the 18° low port SBC heads are worthless compared to the high port 18° heads.
Bret
01-27-2006, 07:46 AM
#6
Originally Posted by SStrokerAce
Ok one more thing....
Valve angle and port height (on the intake flange from the deck) should go together as well....
If you have a shallower valve angle and the same port height you have more issues with your short side radius and more problems with turbulence in the port. There is a relationship to valve angle and port height along with the short side radius.
You can do more things with a shallower valve angle if the rest of the port is built around it. This is one of the reasons the 18° low port SBC heads are worthless compared to the high port 18° heads.
Bret
Valve angle and port height (on the intake flange from the deck) should go together as well....
If you have a shallower valve angle and the same port height you have more issues with your short side radius and more problems with turbulence in the port. There is a relationship to valve angle and port height along with the short side radius.
You can do more things with a shallower valve angle if the rest of the port is built around it. This is one of the reasons the 18° low port SBC heads are worthless compared to the high port 18° heads.
Bret
01-27-2006, 08:04 AM
#7
Originally Posted by GuitsBoy
Basically this means more of a straight shot down the runner and into the bore. that makes sense. Why then do the 11 and 12 degree ls7 heads look like the runner is so low compared to the standard cathedral port in the other lsx heads?
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01-27-2006, 08:23 AM
#10
The runner is the section of port that is on the other side of the bowl. Just like there re runners in the intake manifold, the hallway looking section of the port is also called a runner. Atleast thats what I call it, everyone else be damned! 
