Port cross-section vs throat
Moderator: Team
Port cross-section vs throat
If a intake port on a high rpm (7500 - 9000+) single 4bbl engine has a smaller csa at the entrance and into the port well past the pushrod than the valve throat, will this make more hp to increase this csa to equal or slightly larger than the valve throat. These heads were professionally ported and run very good now. The throat is about 90.5% of 2.15 valve. The rockers are offset and there is room to make these ports bigger(wider or higher).
After cc'ing the port (260cc) and measuring length, the average csa is even smaller than the valve throat area. The port flows the same with the valve (@.800") as with NO valve. This indicates(to me anyway) that it is flow limited by csa back in the port rather than at the valve. The ssr is slightly bigger than the throat. Velocities are ~320 at the pushrod.
Darin Morgan said in his inteview that this never works having the pushrod area or other part of the port smaller. Does that apply to a single 4bbl engine as long as it is a high rpm engine? The engine is relatively small (326) short stroke engine.
Thanks,
Rick
After cc'ing the port (260cc) and measuring length, the average csa is even smaller than the valve throat area. The port flows the same with the valve (@.800") as with NO valve. This indicates(to me anyway) that it is flow limited by csa back in the port rather than at the valve. The ssr is slightly bigger than the throat. Velocities are ~320 at the pushrod.
Darin Morgan said in his inteview that this never works having the pushrod area or other part of the port smaller. Does that apply to a single 4bbl engine as long as it is a high rpm engine? The engine is relatively small (326) short stroke engine.
Thanks,
Rick
-
- Show Guest
- Posts: 1095
- Joined: Tue Nov 02, 2004 10:56 am
- Location: Arlington Texas
- Contact:
Re: Port cross-section vs throat
I have never seen a smaller CA at that push rod than at the throat work on " a properly designed port". HOWEVER,, if your discharge COE. is horrible due to valve shrouding or to big a valve for the bore diameter used or just a very inefficient valve throat chamber combo,,, you may have the port work a little better on the running engine by having the choke or average CA smaller. I refer to it a velocity Band-Aid. If you have a deficiency in the port design. you may be Band-Aid a bad situation. It will show more power on the dyno but that is not the correct way to go about it and the engine will make a lot more power if it where more efficient with a correct velocity profile. I don't know if this is your case or not, but its something to keep in mind. Have you calculated the throat and window area discharge coefficient?Rick360 wrote:If a intake port on a high rpm (7500 - 9000+) single 4bbl engine has a smaller csa at the entrance and into the port well past the pushrod than the valve throat, will this make more hp to increase this csa to equal or slightly larger than the valve throat. These heads were professionally ported and run very good now. The throat is about 90.5% of 2.15 valve. The rockers are offset and there is room to make these ports bigger(wider or higher).
After cc'ing the port (260cc) and measuring length, the average csa is even smaller than the valve throat area. The port flows the same with the valve (@.800") as with NO valve. This indicates(to me anyway) that it is flow limited by csa back in the port rather than at the valve. The ssr is slightly bigger than the throat. Velocities are ~320 at the pushrod.
Darin Morgan said in his inteview that this never works having the pushrod area or other part of the port smaller. Does that apply to a single 4bbl engine as long as it is a high rpm engine? The engine is relatively small (326) short stroke engine.
Thanks,
Rick
Darin Morgan
-Induction Research and Development
-EFI Calibration and Tuning
Reher Morrison Racing Engines
1120 Enterprise Place
Arlington Texas 76001
Phone 817-467-7171
Cell 682-559-0321
http://www.rehermorrison.com
-Induction Research and Development
-EFI Calibration and Tuning
Reher Morrison Racing Engines
1120 Enterprise Place
Arlington Texas 76001
Phone 817-467-7171
Cell 682-559-0321
http://www.rehermorrison.com
Re: Port cross-section vs throat
Darin,
Thanks for responding to my question.
The head is a 23* raised runner with a 2.15" valve (5/16 stem) throat is 1.945" for CA=2.895 sq.in. The bore is 4.030 so the valve is a little big at 53.3%. The chamber is a little bigger (~.040")than the bore and the cylinder is notched out a bit for a smooth transition on the intake side. There is room in these heads to make them as big as the throat area. They have offset jesel rockers and plenty of material at the pushrod area to make them bigger. The manifold is a cast manifold (ported) with 950hp carb.
The flow numbers and D/C's are below using 146cfm/sq.in. theoretical max. These flow #s are from my bench which has matched pretty closely to my pitot tube velocities compared to calculated velocities. The cam has a theoretical net lift of .790"
Flow is at 28"
- Lift - - Flow - - Window D/C - Throat D/C
.200" - - 139 - - - - - .704 - - - - - .329
.300" - - 207 - - - - - .700 - - - - - .489
.400" - - 265 - - - - - .671 - - - - - .626
.500" - - 306 - - - - - .621 - - - - - .724
.600" - - 331 - - - - - .559 - - - - - .783
.700" - - 341 - - - - - .494 - - - - - .806
.800" - - 345 - - - - - .437 - - - - - .816
Thanks,
Rick
Thanks for responding to my question.
The head is a 23* raised runner with a 2.15" valve (5/16 stem) throat is 1.945" for CA=2.895 sq.in. The bore is 4.030 so the valve is a little big at 53.3%. The chamber is a little bigger (~.040")than the bore and the cylinder is notched out a bit for a smooth transition on the intake side. There is room in these heads to make them as big as the throat area. They have offset jesel rockers and plenty of material at the pushrod area to make them bigger. The manifold is a cast manifold (ported) with 950hp carb.
The flow numbers and D/C's are below using 146cfm/sq.in. theoretical max. These flow #s are from my bench which has matched pretty closely to my pitot tube velocities compared to calculated velocities. The cam has a theoretical net lift of .790"
Flow is at 28"
- Lift - - Flow - - Window D/C - Throat D/C
.200" - - 139 - - - - - .704 - - - - - .329
.300" - - 207 - - - - - .700 - - - - - .489
.400" - - 265 - - - - - .671 - - - - - .626
.500" - - 306 - - - - - .621 - - - - - .724
.600" - - 331 - - - - - .559 - - - - - .783
.700" - - 341 - - - - - .494 - - - - - .806
.800" - - 345 - - - - - .437 - - - - - .816
Thanks,
Rick
-
- Show Guest
- Posts: 1095
- Joined: Tue Nov 02, 2004 10:56 am
- Location: Arlington Texas
- Contact:
Re: Port cross-section vs throat
How big is the engine?Rick360 wrote:Darin,
Thanks for responding to my question.
The head is a 23* raised runner with a 2.15" valve (5/16 stem) throat is 1.945" for CA=2.895 sq.in. The bore is 4.030 so the valve is a little big at 53.3%. The chamber is a little bigger (~.040")than the bore and the cylinder is notched out a bit for a smooth transition on the intake side. There is room in these heads to make them as big as the throat area. They have offset jesel rockers and plenty of material at the pushrod area to make them bigger. The manifold is a cast manifold (ported) with 950hp carb.
The flow numbers and D/C's are below using 146cfm/sq.in. theoretical max. These flow #s are from my bench which has matched pretty closely to my pitot tube velocities compared to calculated velocities. The cam has a theoretical net lift of .790"
Flow is at 28"
- Lift - - Flow - - Window D/C - Throat D/C
.200" - - 139 - - - - - .704 - - - - - .329
.300" - - 207 - - - - - .700 - - - - - .489
.400" - - 265 - - - - - .671 - - - - - .626
.500" - - 306 - - - - - .621 - - - - - .724
.600" - - 331 - - - - - .559 - - - - - .783
.700" - - 341 - - - - - .494 - - - - - .806
.800" - - 345 - - - - - .437 - - - - - .816
Thanks,
Rick
What is the operation rpm range for this engine?
If your trying to run the engine in a lower rpm range than its cammed or manifolded for, then you might hold off on increasing the area.
What kind of manifolding is on this engine?
What is the CA at the push rod ( secondary choke area ) ?
You are a little big on valve but that would not hurt that bad if these have a 60/40 valve location. Are they? They do flow rather well for there valve size, bore size ans area. Is there a little left, yes but only about 8 to 10cfm. You wont find another 20 cfm that's for sure. If it where me, and the secondary choke was smaller than the valve, I would take .020 off a wall and put it back on the dyno and see if the trend follows the theory like it always has before. If I didn't have access to a dyno I would do it the way I always have and that would be to make the secondary choke area the same as the throat if not a little larger but the minimum I would go is the same as the throat. You have good flow so it would not scare me to make the area the same as the throat (IF) you are turning the engine high enouph to make it work.
Darin Morgan
-Induction Research and Development
-EFI Calibration and Tuning
Reher Morrison Racing Engines
1120 Enterprise Place
Arlington Texas 76001
Phone 817-467-7171
Cell 682-559-0321
http://www.rehermorrison.com
-Induction Research and Development
-EFI Calibration and Tuning
Reher Morrison Racing Engines
1120 Enterprise Place
Arlington Texas 76001
Phone 817-467-7171
Cell 682-559-0321
http://www.rehermorrison.com
Re: Port cross-section vs throat
326ciDarin Morgan wrote:How big is the engine?
7500-9000 or higher. Converter is 7600 now. Shift at 9000, but will shift higher as ET dictates.Darin Morgan wrote:What is the operation rpm range for this engine?
Cast Aluminum open plenum, ported (tapers to 3.5ca at plenum) (Edelbrock I think) with 950HP Davinci carb. on a large open 2" spacerDarin Morgan wrote:What kind of manifolding is on this engine?
Pushrod area is 2.79sq.in. nowDarin Morgan wrote:What is the CA at the push rod ( secondary choke area ) ?
Yes they are 60/40 valve spacing heads.Darin Morgan wrote:You are a little big on valve but that would not hurt that bad if these have a 60/40 valve location. Are they?
We don't have a dyno , only a race track when it warms up! We were leaning toward making it bigger. We will enlarge it to the size of the throat area.
Thanks a bunch,
Rick
As is usually the case, there were other things changed during this build. Time didn't allow separate testing. Different chassis, headers, some oil pan mods.pont2000 wrote:Hi Rick
I was lurking around and found this old post,,pretty interesting.
I was wondering how this motor finished up? Did you open up the pushrod csa and did the motor like it?
It looks like peak power is around 8300-8400.
Yours is a great question, hope you don't me asking.
col
On the heads.
The SSR velocity were ~420fps range and the SSR was layed back and widened to get the velocities ~380-390fps. The pushrod area was enlarged to the throat CSA. I tried to apply the info that has been shared here.
We believe the HP gains were mostly head related, but probably a combination of SSR velocity and CSA changes. Thanks Larry Meaux and Darin Morgan for sharing all of this info here and on the Speedtalk interview. On the 2 engines/heads I applied this to last year both picked up ET.
The final results...
The new chassis weighed 1580# (weighted to same as old car). The best ET now is (in 1/8th) 4.885 @ 140 with 1.09 60'. (~800'DA). I estimate it to be around 720hp now. Not bad for 23* head 326ci!!
The old combination had best of 5.02 @ 136. We think there is more left in the new combo as there was only time to get a few runs. The chassis was late being built and it wasn't raced til late 2005. The shift point was set at 8800 but I think it would run best shifting above 9000.
Rick
-
- Vendor
- Posts: 3647
- Joined: Sat Feb 14, 2004 4:04 pm
- Location: Abbeville, LA
- Contact:
glad to hear that Info helped you out !On the heads.
The SSR velocity were ~420fps range and the SSR was layed back and widened to get the velocities ~380-390fps. The pushrod area was enlarged to the throat CSA. I tried to apply the info that has been shared here.
We believe the HP gains were mostly head related, but probably a combination of SSR velocity and CSA changes. Thanks Larry Meaux and Darin Morgan for sharing all of this info here and on the Speedtalk interview. On the 2 engines/heads I applied this to last year both picked up ET