High Flow, Low Cost, 8V Cylinder Head Project
06-20-2012, 01:21 AM
#76
Rennlist Member
I am still at a loss that this supposed 300+cfm is readily available on an 8v head?
06-20-2012, 04:29 AM
#77
Nordschleife Master
).I'm sure that it will flow more or less similar to the best heads seen around here when comparing the same lift.
06-20-2012, 04:49 AM
#78
Rennlist Member
Yes I saw that Gustaf but even comparing it at say .500" to the head on my 3L which was 240cfm, his is 272cfm. Is this still Apple to Oranges? Or does the different cams make comparing at same lift unreasonable? What makes it further interesting is that from what I can see on post #32 he states the standard intake at .500" flows 212cfm when our standard 8v head is cited to flow ~180cfm...so I'm sure I'm not reading this correctly. https://rennlist.com/forums/928-foru...-update-3.html
Does the 8v head on the 928 flow differently due to the V8 configuration? Also wondering what the our standard head is meant to flow on exhaust, this being the lesser number?
Does the 8v head on the 928 flow differently due to the V8 configuration? Also wondering what the our standard head is meant to flow on exhaust, this being the lesser number?
06-20-2012, 05:09 AM
#80
Rennlist Member
Something is either staring me in the face or it just doesn't add up? Can flow benches be subjective like dyno's? I wouldn't have thought so as there is no actual load apart from air or water being sent through at a predetermined rate. 28 somethings...
06-20-2012, 08:37 AM
#81
Three Wheelin'
Contact him he really enjoys tecnical discussions. In the 928 world there was an enthusiasst named Bob Devore. He built a 2 valve 928 that supposedly had over 700 hp NA. He became apart of a company called Devek that pioneered large bore stroker 928's decades ago. His big motor ran 944 heads.
06-20-2012, 09:00 AM
#82
Rennlist Member
Yes I've heard and read of Devek. 700hp n/a is crazy stuff. What size do they stroke these motors out to?
Also, I wasn't banging on about the cfm as if it was the be all and end all. As we know velocity is just as, or more important than volume...but numbers is numbers...I still wonder what they're doing that is so different to the 944 world?? I'd like to engage Mr S. Blue in a conversation but he'd run rings around my tech knowledge. Be more than happy to have one of our more credentialed colleagues have a chat with him and watch on. Anyone care to open up the forum?
Also, I wasn't banging on about the cfm as if it was the be all and end all. As we know velocity is just as, or more important than volume...but numbers is numbers...I still wonder what they're doing that is so different to the 944 world?? I'd like to engage Mr S. Blue in a conversation but he'd run rings around my tech knowledge. Be more than happy to have one of our more credentialed colleagues have a chat with him and watch on. Anyone care to open up the forum?
06-20-2012, 09:25 AM
#84
Rennlist Member
Indeed!!
I sent a pm to Mr S.Blue to see if he'd engage us in a discussion. Not sure he is a super regular poster so we shall see what happens. Not that I'll understand everything but I like to learn and engender these sort of threads. Hopefully Shawn won't mind some outside interaction.
I sent a pm to Mr S.Blue to see if he'd engage us in a discussion. Not sure he is a super regular poster so we shall see what happens. Not that I'll understand everything but I like to learn and engender these sort of threads. Hopefully Shawn won't mind some outside interaction.
06-20-2012, 07:56 PM
#85
Ok I was asked to clarify some details of the development that was done years ago on the 928 2 valve heads. First the 944 and 928 heads are similar but not the same due to their valve spacing and combustion chamber.
The 928 head traditionally was fitted to 95 or 97 mm bore whereas the 944 head gets fitted to 100 or 104 mm bore. So the factory designers changed the valve spacing, there is extra width 3.5 mm of valve spacing. I haven't looked at this for quite some time so my memory is a bit hazy on how they moved them.
I know they moved the valves 1.5 mm and 2 mm and if I was to have a guess the exhaust was moved over 2 mm closer to the cylinder wall and the intake moved over 1.5 mm closer to the wall. So more shrouding effectively, however sometimes the way the wall can interact with the flow to assist, i.e forms part of a diffuser, not saying that is happening here though, also it will probably change with different lifts.
The flow of the standard port was done on a decarbonized port and valve with the standard 97 mm bore and I am aware others on the 928 forum have achieved similar numbers. Again from memory we then tidied up the port, different cuts on the seat etc and got around 230 cfm.
The fellow at the race shop then agreed that a larger valve may well help with the ability to shape the port as much as just making the "hole" bigger. He didn't make the port bigger at all but raised the roof quite a lot and was able to develop a better short side which we checked with a silicon mold. The valve used was the 944 2.7L 48 mm valve.
That yielded a result at peak lift of 246 cfm. I believe we used the lift figure of 0472". I was really on a learning curve at this early stage. I believe heads like these would really preform very well and judging by what the cleaned up heads did (which flowed around 230 cfm) with standard valves on a standard bottom end. The engine had excellent pulling power and drivability. It did have other mods such as an elaborate exhaust with variable flow. It also had a cleaned up plenum and intake runners.
I intended to build a separate much bigger engine and had a stroker bottom end waiting to go. The guys that were advising me were always stressing the right port sizing and saying go smaller rather than larger given the intended use.
We decided to go a larger valve, larger on both sides in fact, 2.10" and 1.65" the bore was 103 mm. I used the standard numbers as a reference. A key number was the flow per sq inch of valve area. 87 cfm was the number at 0.500" and that was my immediate goal to achieve that number with the bigger valve.
It took a lot of experimentation to get their. The best figure was 304 cfm at 0.500". However the flow tapered off above this lift, the planned lift was 0.650". That port achieved around 315 cfm at peak lift whereas another port did 292 and 325 cfm respectively. Shows how you can tailor you port to your cam.
The CSA was really too small to take advantage of all that flow, average CSA was 2.15 sq". The port couldn't be increased in size any further due to the casting. The 944 standard casting would probably be better. I did consider using the bigger heads but that never happened.
The only way I was able to achieve such numbers was to fill the floor and raise the roof. You also need a development head which you can section and port molding material to see the shape of your ports. The early ports were not filled.
The idea I had but never tested was with the 2.7L head, these heads like all of the similar series of heads starts to shroud the valve at the higher the lift. A NASCAR head is completely different, the more lift equals less shrouding. This is achieved by canting the valve and the twisted placement of the valves.
The difference is and forgetting about the cant, with a 944 or 928 head the valve starts in the centre of the bore and then migrates away from the centerline and gets closer to the bore as it decends on it's inclined angle which is 20 degrees.
Whereas a NASCAR head valve starts off the centre of the bore, (the reason for the twisted design along with a better steeper short side) and as it decends it comes to the centreline of the bore for maximum unshrouding. They then cant the valve for further bore clearance. These heads can achieve around 100 cfm at 0.500" per sq" of valve area and at 0.800" around 114 cfm.
So my idea was to move the intake valve over and away from the bore and make the bore bigger, much bigger like others have done in the 109 to 110 mm range. With a 2.20" valve and the flat floor the 2.7L port has and around 5 mm to 7 mm wall clearance, I would estimate flow up to 330 cfm at 0.500" and around 350 cfm at a peak lift of 0.650". In a big capacity high speed engine that would have made a lot of power.
The 928 head traditionally was fitted to 95 or 97 mm bore whereas the 944 head gets fitted to 100 or 104 mm bore. So the factory designers changed the valve spacing, there is extra width 3.5 mm of valve spacing. I haven't looked at this for quite some time so my memory is a bit hazy on how they moved them.
I know they moved the valves 1.5 mm and 2 mm and if I was to have a guess the exhaust was moved over 2 mm closer to the cylinder wall and the intake moved over 1.5 mm closer to the wall. So more shrouding effectively, however sometimes the way the wall can interact with the flow to assist, i.e forms part of a diffuser, not saying that is happening here though, also it will probably change with different lifts.
The flow of the standard port was done on a decarbonized port and valve with the standard 97 mm bore and I am aware others on the 928 forum have achieved similar numbers. Again from memory we then tidied up the port, different cuts on the seat etc and got around 230 cfm.
The fellow at the race shop then agreed that a larger valve may well help with the ability to shape the port as much as just making the "hole" bigger. He didn't make the port bigger at all but raised the roof quite a lot and was able to develop a better short side which we checked with a silicon mold. The valve used was the 944 2.7L 48 mm valve.
That yielded a result at peak lift of 246 cfm. I believe we used the lift figure of 0472". I was really on a learning curve at this early stage. I believe heads like these would really preform very well and judging by what the cleaned up heads did (which flowed around 230 cfm) with standard valves on a standard bottom end. The engine had excellent pulling power and drivability. It did have other mods such as an elaborate exhaust with variable flow. It also had a cleaned up plenum and intake runners.
I intended to build a separate much bigger engine and had a stroker bottom end waiting to go. The guys that were advising me were always stressing the right port sizing and saying go smaller rather than larger given the intended use.
We decided to go a larger valve, larger on both sides in fact, 2.10" and 1.65" the bore was 103 mm. I used the standard numbers as a reference. A key number was the flow per sq inch of valve area. 87 cfm was the number at 0.500" and that was my immediate goal to achieve that number with the bigger valve.
It took a lot of experimentation to get their. The best figure was 304 cfm at 0.500". However the flow tapered off above this lift, the planned lift was 0.650". That port achieved around 315 cfm at peak lift whereas another port did 292 and 325 cfm respectively. Shows how you can tailor you port to your cam.
The CSA was really too small to take advantage of all that flow, average CSA was 2.15 sq". The port couldn't be increased in size any further due to the casting. The 944 standard casting would probably be better. I did consider using the bigger heads but that never happened.
The only way I was able to achieve such numbers was to fill the floor and raise the roof. You also need a development head which you can section and port molding material to see the shape of your ports. The early ports were not filled.
The idea I had but never tested was with the 2.7L head, these heads like all of the similar series of heads starts to shroud the valve at the higher the lift. A NASCAR head is completely different, the more lift equals less shrouding. This is achieved by canting the valve and the twisted placement of the valves.
The difference is and forgetting about the cant, with a 944 or 928 head the valve starts in the centre of the bore and then migrates away from the centerline and gets closer to the bore as it decends on it's inclined angle which is 20 degrees.
Whereas a NASCAR head valve starts off the centre of the bore, (the reason for the twisted design along with a better steeper short side) and as it decends it comes to the centreline of the bore for maximum unshrouding. They then cant the valve for further bore clearance. These heads can achieve around 100 cfm at 0.500" per sq" of valve area and at 0.800" around 114 cfm.
So my idea was to move the intake valve over and away from the bore and make the bore bigger, much bigger like others have done in the 109 to 110 mm range. With a 2.20" valve and the flat floor the 2.7L port has and around 5 mm to 7 mm wall clearance, I would estimate flow up to 330 cfm at 0.500" and around 350 cfm at a peak lift of 0.650". In a big capacity high speed engine that would have made a lot of power.
06-20-2012, 08:24 PM
#86
Rennlist Member
Thread Starter
Ok I was asked to clarify some details of the development that was done years ago on the 928 2 valve heads. First the 944 and 928 heads are similar but not the same due to their valve spacing and combustion chamber.
The 928 head traditionally was fitted to 95 or 97 mm bore whereas the 944 head gets fitted to 100 or 104 mm bore. So the factory designers changed the valve spacing, there is extra width 3.5 mm of valve spacing. I haven't looked at this for quite some time so my memory is a bit hazy on how they moved them.
I know they moved the valves 1.5 mm and 2 mm and if I was to have a guess the exhaust was moved over 2 mm closer to the cylinder wall and the intake moved over 1.5 mm closer to the wall. So more shrouding effectively, however sometimes the way the wall can interact with the flow to assist, i.e forms part of a diffuser, not saying that is happening here though, also it will probably change with different lifts.
The flow of the standard port was done on a decarbonized port and valve with the standard 97 mm bore and I am aware others on the 928 forum have achieved similar numbers. Again from memory we then tidied up the port, different cuts on the seat etc and got around 230 cfm.
The fellow at the race shop then agreed that a larger valve may well help with the ability to shape the port as much as just making the "hole" bigger. He didn't make the port bigger at all but raised the roof quite a lot and was able to develop a better short side which we checked with a silicon mold. The valve used was the 944 2.7L 48 mm valve.
That yielded a result at peak lift of 246 cfm. I believe we used the lift figure of 0472". I was really on a learning curve at this early stage. I believe heads like these would really preform very well and judging by what the cleaned up heads did (which flowed around 230 cfm) with standard valves on a standard bottom end. The engine had excellent pulling power and drivability. It did have other mods such as an elaborate exhaust with variable flow. It also had a cleaned up plenum and intake runners.
I intended to build a separate much bigger engine and had a stroker bottom end waiting to go. The guys that were advising me were always stressing the right port sizing and saying go smaller rather than larger given the intended use.
We decided to go a larger valve, larger on both sides in fact, 2.10" and 1.65" the bore was 103 mm. I used the standard numbers as a reference. A key number was the flow per sq inch of valve area. 87 cfm was the number at 0.500" and that was my immediate goal to achieve that number with the bigger valve.
It took a lot of experimentation to get their. The best figure was 304 cfm at 0.500". However the flow tapered off above this lift, the planned lift was 0.650". That port achieved around 315 cfm at peak lift whereas another port did 292 and 325 cfm respectively. Shows how you can tailor you port to your cam.
The CSA was really too small to take advantage of all that flow, average CSA was 2.15 sq". The port couldn't be increased in size any further due to the casting. The 944 standard casting would probably be better. I did consider using the bigger heads but that never happened.
The only way I was able to achieve such numbers was to fill the floor and raise the roof. You also need a development head which you can section and port molding material to see the shape of your ports. The early ports were not filled.
The idea I had but never tested was with the 2.7L head, these heads like all of the similar series of heads starts to shroud the valve at the higher the lift. A NASCAR head is completely different, the more lift equals less shrouding. This is achieved by canting the valve and the twisted placement of the valves.
The difference is and forgetting about the cant, with a 944 or 928 head the valve starts in the centre of the bore and then migrates away from the centerline and gets closer to the bore as it decends on it's inclined angle which is 20 degrees.
Whereas a NASCAR head valve starts off the centre of the bore, (the reason for the twisted design along with a better steeper short side) and as it decends it comes to the centreline of the bore for maximum unshrouding. They then cant the valve for further bore clearance. These heads can achieve around 100 cfm at 0.500" per sq" of valve area and at 0.800" around 114 cfm.
So my idea was to move the intake valve over and away from the bore and make the bore bigger, much bigger like others have done in the 109 to 110 mm range. With a 2.20" valve and the flat floor the 2.7L port has and around 5 mm to 7 mm wall clearance, I would estimate flow up to 330 cfm at 0.500" and around 350 cfm at a peak lift of 0.650". In a big capacity high speed engine that would have made a lot of power.
The 928 head traditionally was fitted to 95 or 97 mm bore whereas the 944 head gets fitted to 100 or 104 mm bore. So the factory designers changed the valve spacing, there is extra width 3.5 mm of valve spacing. I haven't looked at this for quite some time so my memory is a bit hazy on how they moved them.
I know they moved the valves 1.5 mm and 2 mm and if I was to have a guess the exhaust was moved over 2 mm closer to the cylinder wall and the intake moved over 1.5 mm closer to the wall. So more shrouding effectively, however sometimes the way the wall can interact with the flow to assist, i.e forms part of a diffuser, not saying that is happening here though, also it will probably change with different lifts.
The flow of the standard port was done on a decarbonized port and valve with the standard 97 mm bore and I am aware others on the 928 forum have achieved similar numbers. Again from memory we then tidied up the port, different cuts on the seat etc and got around 230 cfm.
The fellow at the race shop then agreed that a larger valve may well help with the ability to shape the port as much as just making the "hole" bigger. He didn't make the port bigger at all but raised the roof quite a lot and was able to develop a better short side which we checked with a silicon mold. The valve used was the 944 2.7L 48 mm valve.
That yielded a result at peak lift of 246 cfm. I believe we used the lift figure of 0472". I was really on a learning curve at this early stage. I believe heads like these would really preform very well and judging by what the cleaned up heads did (which flowed around 230 cfm) with standard valves on a standard bottom end. The engine had excellent pulling power and drivability. It did have other mods such as an elaborate exhaust with variable flow. It also had a cleaned up plenum and intake runners.
I intended to build a separate much bigger engine and had a stroker bottom end waiting to go. The guys that were advising me were always stressing the right port sizing and saying go smaller rather than larger given the intended use.
We decided to go a larger valve, larger on both sides in fact, 2.10" and 1.65" the bore was 103 mm. I used the standard numbers as a reference. A key number was the flow per sq inch of valve area. 87 cfm was the number at 0.500" and that was my immediate goal to achieve that number with the bigger valve.
It took a lot of experimentation to get their. The best figure was 304 cfm at 0.500". However the flow tapered off above this lift, the planned lift was 0.650". That port achieved around 315 cfm at peak lift whereas another port did 292 and 325 cfm respectively. Shows how you can tailor you port to your cam.
The CSA was really too small to take advantage of all that flow, average CSA was 2.15 sq". The port couldn't be increased in size any further due to the casting. The 944 standard casting would probably be better. I did consider using the bigger heads but that never happened.
The only way I was able to achieve such numbers was to fill the floor and raise the roof. You also need a development head which you can section and port molding material to see the shape of your ports. The early ports were not filled.
The idea I had but never tested was with the 2.7L head, these heads like all of the similar series of heads starts to shroud the valve at the higher the lift. A NASCAR head is completely different, the more lift equals less shrouding. This is achieved by canting the valve and the twisted placement of the valves.
The difference is and forgetting about the cant, with a 944 or 928 head the valve starts in the centre of the bore and then migrates away from the centerline and gets closer to the bore as it decends on it's inclined angle which is 20 degrees.
Whereas a NASCAR head valve starts off the centre of the bore, (the reason for the twisted design along with a better steeper short side) and as it decends it comes to the centreline of the bore for maximum unshrouding. They then cant the valve for further bore clearance. These heads can achieve around 100 cfm at 0.500" per sq" of valve area and at 0.800" around 114 cfm.
So my idea was to move the intake valve over and away from the bore and make the bore bigger, much bigger like others have done in the 109 to 110 mm range. With a 2.20" valve and the flat floor the 2.7L port has and around 5 mm to 7 mm wall clearance, I would estimate flow up to 330 cfm at 0.500" and around 350 cfm at a peak lift of 0.650". In a big capacity high speed engine that would have made a lot of power.
06-20-2012, 08:29 PM
#87
Rennlist Member
Thread Starter
Final cost fot the project which included used head (bent valves), new guides, new intake valves (47mm), new exhaust valves, new seals, competition valve job, deck (0.010") was $693 complete. This does not include flow testing costs.
06-20-2012, 08:31 PM
#88
Rennlist Member
Thread Starter
Indeed!!
I sent a pm to Mr S.Blue to see if he'd engage us in a discussion. Not sure he is a super regular poster so we shall see what happens. Not that I'll understand everything but I like to learn and engender these sort of threads. Hopefully Shawn won't mind some outside interaction.
I sent a pm to Mr S.Blue to see if he'd engage us in a discussion. Not sure he is a super regular poster so we shall see what happens. Not that I'll understand everything but I like to learn and engender these sort of threads. Hopefully Shawn won't mind some outside interaction.
06-20-2012, 10:22 PM
#89
With regards to port finish, rough on the short turn radius, I used 40 grit paper on the floor and turn in the direction of the airflow to try and create rib lets to keep the air attached over the turn. The rest of the port is fairly smooth but is much straighter than the short turn so you don't want such turbulence there.
I'll have to sign off here, I not well and that is the reason the project never proceeded and the reason I don't post much anymore, not looking for sympathy but I don't want you guys to think I am rude by not responding any further. Thanks
I'll have to sign off here, I not well and that is the reason the project never proceeded and the reason I don't post much anymore, not looking for sympathy but I don't want you guys to think I am rude by not responding any further. Thanks
06-20-2012, 10:28 PM
#90
Rennlist Member
Thread Starter
With regards to port finish, rough on the short turn radius, I used 40 grit paper on the floor and turn in the direction of the airflow to try and create rib lets to keep the air attached over the turn. The rest of the port is fairly smooth but is much straighter than the short turn so you don't want such turbulence there.
I'll have to sign off here, I not well and that is the reason the project never proceeded and the reason I don't post much anymore, not looking for sympathy but I don't want you guys to think I am rude by not responding any further. Thanks
I'll have to sign off here, I not well and that is the reason the project never proceeded and the reason I don't post much anymore, not looking for sympathy but I don't want you guys to think I am rude by not responding any further. Thanks
Thanks for taking the time to give us some feedback. Hope you feel better soon.
