Valve Angle thoughts

[pclowes]

Just thinking out loud and maybe way out of the box but am wondering if a low riser head would benefit with a valve angle closer to what the original SBC had at 23 degrees.  Just thinking that flow through the port itself would benefit.   Could be that after it gets past the valve the flow at  larger valve openings would be shrouded more but the increase in flow through the port at lower openings, because of the straighter shot, might offset that. Thinking more for street use at lower lifts.

Just thinking that the original SBC at 23 degrees performed so well for so many years and while decreasing the angle to 18 degrees and finally, I believe, to 13 degrees ( same as all FE's?) did increase performance it also required raising the ports and manifold to take advantage of the smaller valve angle. This was the reason for the medium and high rise FE's.  Raising the ports was simply taking advantage of the already small FE valve angle.  A larger valve angle would let the already low ports on the low riser heads and manifold perform better.

Probably backwards thinking and probably not even feasible especially when talking of compatibility with the traditional FE shaft rocker system. Not even sure of a market for such a head although there may be more users that would want something that may perform better for street use and still fit under the hood.  I know most medium riser setups will fit under the hood but they might also benefit from less of an angle (18 degrees?) in certain circumstances.  Probably would take some fancy mockups on a flow bench to prove or disprove.
There is still a market for 23 degree SBC heads even though the 18 and 13 degree versions have more power potential.

Am I way out of the ballpark or just in left field?  Most likely this subject has already been talked about (most likely when Edelbrock was developing their FE head).

Thinking further (I get in trouble every time I try that) the traditional, half of a head, FE architecture probably would place the rocker shaft pedestals into the manifold side of the head for a rocker system that would be compatible with anything more than the current angle.  Probably why it's never been done.

[jayb]

Increasing the FE valve angle would certainly help flow, although the effect of the flow hitting the cylinder wall would negate that to some extent.  Modern design is more about increasing the valve angle, so that the flow into the cylinder is not compromised as much by the cylinder wall, and raising the port/intake to match.

If you were to try to increase the FE valve angle, I think you are correct that the whole rocker and shaft situation would change.  If you are going to try to improve flow, its a lot easier to just raise the port, and you still keep the benefit of the fairly steep 12 degree valve angle.

[pclowes]

Increasing the FE valve angle would certainly help flow, although the effect of the flow hitting the cylinder wall would negate that to some extent.  Modern design is more about increasing the valve angle, so that the flow into the cylinder is not compromised as much by the cylinder wall, and raising the port/intake to match.

If you were to try to increase the FE valve angle, I think you are correct that the whole rocker and shaft situation would change.  If you are going to try to improve flow, its a lot easier to just raise the port, and you still keep the benefit of the fairly steep 12 degree valve angle.

I was thinking mostly about improving flow in the low riser heads.  I didn't think it through enough, however.  Because of the necessary rocker arm system relocation, none of the existing low rise manifolds would work with any new head with an increased valve angle. It would be counterproductive for a number of reasons, cost being one but also the traditional look of the unique FE head design would surely change. Don't want that. Have to leave well enough alone for now.

[pclowes]

Increasing the FE valve angle would certainly help flow, although the effect of the flow hitting the cylinder wall would negate that to some extent.  Modern design is more about increasing the valve angle, so that the flow into the cylinder is not compromised as much by the cylinder wall, and raising the port/intake to match.

If you were to try to increase the FE valve angle, I think you are correct that the whole rocker and shaft situation would change.  If you are going to try to improve flow, its a lot easier to just raise the port, and you still keep the benefit of the fairly steep 12 degree valve angle.

 
I was thinking mostly about improving flow in the low riser heads.  I didn't think it through enough, however.  Because of the necessary rocker arm system relocation, none of the existing low rise manifolds would work with any new head with an increased valve angle. It would be counterproductive for a number of reasons, cost being one but also the traditional look of the unique FE head design would surely change. Don't want that. Have to leave well enough alone for now.

Also, while leaning the valves over helps the intake it would hurt the exhaust.  That would require raising the exhaust port.  Then again, I suppose the exhaust valve could stay where it's at.  But then you would end up with two different length rocker arms on a common shaft system.

[TomP]

Where would you attach these rocker shafts? The stands would need to be on the intake, the valve covers will need to a bunch wider. Besides, they have similar engines already... called 460's.

[pclowes]

Where would you attach these rocker shafts? The stands would need to be on the intake, the valve covers will need to a bunch wider. Besides, they have similar engines already... called 460's.

You're right that the rocker system would end up in the manifold area, You probably missed that I stated that in the last paragraph of my initial posting. However, I think the rocker cover could stay the same dimension because the area of the manifold that the rocker would move to is already under the valve cover due to the fe's unique, what I call 1/2 of a head, design.  The drawback is that the head and manifold would end up looking like every other out there, instead of the look that only the fe design has.
 
Also I was trying to stay with a traditional wedge shape with an inline valve arrangement and did not want to go to a canted valve layout like the 429/460 even though it is a better breathing configuration, IMO.

I wanted to stay within the traditional fe architecture but I can see that it would stray too far from that. In the end I do agree it would be too much work with little payoff, especially since I was aiming the design toward low riser heads.

[Royce]

Take a look at how a Buick nailhead tackles the problem of rocker arm configuration when you change the valve angle.

[pclowes]

Where would you attach these rocker shafts? The stands would need to be on the intake, the valve covers will need to a bunch wider. Besides, they have similar engines already... called 460's.

You're right that the rocker system would end up in the manifold area, You probably missed that I stated that in the last paragraph of my initial posting. However, I think the rocker cover could stay the same dimension because the area of the manifold that the rocker would move to is already under the valve cover due to the fe's unique, what I call 1/2 of a head, design.  The drawback is that the head and manifold would end up looking like every other out there, instead of the look that only the fe design has.



 
Also I was trying to stay with a traditional wedge shape with an inline valve arrangement and did not want to go to a canted valve layout like the 429/460 even though it is a better breathing configuration, IMO.

I wanted to stay within the traditional fe architecture but I can see that it would stray too far from that. In the end I do agree it would be too much work with little payoff, especially since I was aiming the design toward low riser heads.

One last thought.  The valve angle for Windsor design small block Ford heads is 21 degrees.  I don't see any reason that the resulting valve cover width, after increasing the fe valve angle, would be any wider than that small block cover.  However, repeating myself, the rockers would most likely encroach into the manifold area that is currently under the valve cover of the fe as we now know it. Might have to go pedestal style rockers. Not sure.