Hi All,
I am struggling to get decent exhaust flow on 23 deg Chevy heads, can someone please give me some idea's or even better part #s that flow well
Just stainless stuff not to exotic plz.
I have been using 1.600" Manley pro flo's but they have a shallow tulip shape
And not a lot of margin.
Will a very high tulip shape with a large radiused margin help ?
Run approx 89 -91 % throat.
Will going to a 1.65" Ex valve help airflow much ?
Intake is no probs just exhaust, and am willing to sacrifice intake valve size for more exhaust.
Thanks
Gary.
23 deg exhaust valve
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bill jones
- Guru
- Posts: 2650
- Joined: Sun Sep 05, 2004 6:38 pm
- Location: salt lake city, ut
- Contact:
-Manley has a #11557 that I like.
-1.625", 30 degree tulip, 4.921" long, 25 degree dish in the chamber side, and a .070" margin.
-I always have trouble with bowls that are already too large or that have been cut too steep into the bowl.
-I prefer the bowls to be smaller than 1.320" and I don't like the throat exactly centered, I don't like it exactly round and I find that the throat needs to be offset towards the short turn.
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-In the chambers, I like to have a concave cusp (undercut) in the corner from the shroud around towards the center of the chamber on the quench pad side.
-Everytime I see that area laid back and rolled into the seat.
-There seems to be something about that cusp that grabs the air and gets more air thru the port.
---------------------------------
-I use equal width 37 and 29 degree backcuts on the valve and then I swirl polish right over those backcuts right to and remove the bottom demarcation line for the seat angle.
-I use a 52 degree or maybe a 54 degree bowl cut and HANDBLEND the throats to where there is NO demarcation lines whatsoever near the exhaust seat.
-All you see there is nearly like a slightly distorted donut with a narrow seat angle.
-I lightly flap right across the seat and polish from the chamber across the seat and into the bowl and across the short turn.
-Then I go back and lightly retouch where the seat is.
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-This doesn't necessarily get the biggest flow numbers at max lift but it sure pumps up the mid lift from about .275" lift.
-I like to see about 169 to 182 at .300" (at 28") and 184 to 206 at .400" and then I really don't worry too much about the high lift numbers as long as they are 200 to 223 at .600", and this is with a bare port-no extension header tube.
-1.625", 30 degree tulip, 4.921" long, 25 degree dish in the chamber side, and a .070" margin.
-I always have trouble with bowls that are already too large or that have been cut too steep into the bowl.
-I prefer the bowls to be smaller than 1.320" and I don't like the throat exactly centered, I don't like it exactly round and I find that the throat needs to be offset towards the short turn.
------------------------------------
-In the chambers, I like to have a concave cusp (undercut) in the corner from the shroud around towards the center of the chamber on the quench pad side.
-Everytime I see that area laid back and rolled into the seat.
-There seems to be something about that cusp that grabs the air and gets more air thru the port.
---------------------------------
-I use equal width 37 and 29 degree backcuts on the valve and then I swirl polish right over those backcuts right to and remove the bottom demarcation line for the seat angle.
-I use a 52 degree or maybe a 54 degree bowl cut and HANDBLEND the throats to where there is NO demarcation lines whatsoever near the exhaust seat.
-All you see there is nearly like a slightly distorted donut with a narrow seat angle.
-I lightly flap right across the seat and polish from the chamber across the seat and into the bowl and across the short turn.
-Then I go back and lightly retouch where the seat is.
--------------------------------------------
-This doesn't necessarily get the biggest flow numbers at max lift but it sure pumps up the mid lift from about .275" lift.
-I like to see about 169 to 182 at .300" (at 28") and 184 to 206 at .400" and then I really don't worry too much about the high lift numbers as long as they are 200 to 223 at .600", and this is with a bare port-no extension header tube.
Thankyou Bill, I am not getting near those numbers and would be over the moon if I could get close.
I have a ton of compression to get rid of so dont mind getting stuck into the chambers where ever I can.
Thanks Bill
Gary.
Not sure if you are saying to lay back quench side or not ?In the chambers, I like to have a concave cusp (undercut) in the corner from the shroud around towards the center of the chamber on the quench pad side.
-Everytime I see that area laid back and rolled into the seat.
I have a ton of compression to get rid of so dont mind getting stuck into the chambers where ever I can.
Thanks Bill
Gary.
-
bill jones
- Guru
- Posts: 2650
- Joined: Sun Sep 05, 2004 6:38 pm
- Location: salt lake city, ut
- Contact:
-that corner has a natural cusp already built into most 23 degree heads I see.
-Some people tend to lay that back and remove the cusp or remove most of the sharp edge of the cusp.
-I don't know what it is but on BBC cast iron heads and SBC's and some other heads my porting says to leave that cusp there and if you do anything, slightly exaggerate it and sharpen it up.
-Some people tend to lay that back and remove the cusp or remove most of the sharp edge of the cusp.
-I don't know what it is but on BBC cast iron heads and SBC's and some other heads my porting says to leave that cusp there and if you do anything, slightly exaggerate it and sharpen it up.