quote:Originally posted by George P:
With a valve seat angle of 45° air flow increase shall be most linear as valve lift increases. Valve seat angles straying from 45° create a non-linearity. Valve seat angles greater than 45° shall favor high lift flow, valve seat angles less than 45° shall favor low lift flow.
I knew theory about angles but in fact I did not wanted to go too deep into modifications, this is my first engine build.
I took EPN stainless steel valves they are 45°
quote:Originally posted by George P:
The 351C 4V intake port, out of the box, has a valve pocket throat diameter of approximately 1.75" (2.40 square inches area), and will thus reach the limiting port velocity (sonic choke) at 7344 rpm (357 cubic inches). Whatever you do, do not "open-up" the valve pocket throat diameter more than 1.90 (2.83 square inches area). Opening up the throat larger than that will negatively impact the intake port's performance. At that throat diameter limiting port velocity is reached at 8660 rpm.
In fact this is a bit the big question. Should I remove this ring, basically I was thinking no. And what you said tend to go in the same direction since I don't want to go over 7000 rpm, as things will start to really suffer. So what I was asking my self is, should I smooth the ring edge a little bit or reduce it but a little in order to have a best shape for flow but keeping it function of booster ring ?
quote:Originally posted by George P:
The quench chamber heads shroud both the intake and exhaust valves in places, and air flow (especially low lift air flow) can be improved with a bit of "un-shrouding" in the combustion chamber. As is true for any cylinder head, you want a nice, smooth, well blended transition from the valve pocket to the throat, a "rounded" throat, a nice, smooth, well blended transition from the throat to the valve seat, and from the valve seat into the combustion chamber. No recessed valve seats. Recessed valve seats must be blended to remove the sharp edges and smoothly blend the seat into the combustion chamber, or seat inserts can be installed to thus eliminate the recessed seats. This detail work will net you the most performance from the cylinder heads.
When you talk about shrouding are you talking about what is on the path of the air when the valve is lifted ? (for the low lift that is clear I will blend to have smooth transitions)
For example here :
I was thinking for intake taht from 12 to 2 PM that it was possible to unshroud by reducing a little bit the squish area, For exhaust same at 12 to 2.
Last think at 6 to 7 on intake there's a sharp edge, should I remove it ?
quote:Originally posted by George P:
If your headers (or exhaust manifolds) are the type that turn-down and hug the engine then you want to leave the flat roof & the bump in the exhaust port, and also leave the exhaust port floor as-is. Those features in the exhaust port were put there to aid the port's performance when the headers/manifolds turn abruptly downward.
As you saw I've made a port, I understood that it was needed to remove this bump in the roof, so I cut it.
On exhaust polishing can alway be better ?
quote:Originally posted by George P:
Intake valve seat width no less than 0.060", exhaust valve seat width no less than 0.080", and seat run-out no greater than 0.001".
Ok but I need to sketch the valve and seats, the problem is that I don't know if the valve contact with seat should be in the inner side of the valve 45° surface, or outer side ?
quote:Originally posted by George P:
Here's a picture of outstanding intake valve pocket & valve seat work. The combustion chamber could stand some un-shrouding at about 4 o'clock, and from 6 to 8 o'clock. However the un-shrouding from 6 to 8 o'clock should stay within the boundary set by the head gasket. The un-shrouding from 6 to 8 o'clock may have already been done to the cylinder head in the picture, its that tight.
crazy work.
How can I polish iron like that ?