Head Flow numbers
10-19-2003, 02:43 PM
#1
Head Flow numbers
After recieving many requests to provide the Flow numbers, I am going to ask Performance Developments to flow a Head just off an engine. They may have done this already. If they haven't, I will ask them to. Then a true comparision can be had. A typical before and after test.
10-20-2003, 11:10 PM
#2
As promised,here are the numbers I got today. These numbers are after a typical repair,(valve job) and are what should be expected after proper repair work is done on existing seats. I'm told slightly higher numbers can be expected when the seat is at its highest, (first time or after seat insert is replaced).
The Flow numbers were done on Performance Developments SF600 Flow Bench @ 25" H2O, every 0.05" on a Stock Head with no other work, but a Multi angle/ radius Valve job. The original Valve seats were the standard 3 angles, touched up and pulled over 0.7b vacuum on their Serdi.
BTW, I asked today about the different test pressures. I was told that the Superflow Flow 600 benches are calibrated at 25" of water, and there is no correction factors required.
Stock angles PD Multi Radius Stock PD Multi Radius
IN IN EX EX
23.1 29.8 19.9 24.7
47.0 56.0 44.6 55.1
77.7 87.8 70.6 86.2
105.8 116.3 93.8 109.0
133.7 143.6 105.8 116.8
147.6 161.3 121.7 134.6
162.3 174.2 132.9 144.8
171.0 187.2 143.8 157.2
178.7 196.8 149.4 163.6
186.7 202.9 151.2 166.8
The lifts as measured are 0.472 In and 0.437 EX. The last row of numbers on the Intake are beyond the max stock lift, and the last 2 rows on the exhaust are beyond the max stock lift. They just show the flow potential.
It has been stated many time before that the new style multi angles/radius seats work better than the old style 3 angles. PD will not tell me the angles/ radi's and number of them used, nor any other little tricks to help with the flow.
I did ask PD what their typical cost to do a Head complete is. This is how they do it. You call them and they will UPS a shipping box to you to put the Head in. This saves you time and the box is made just for that Head. It even comes addressed back to Performance Developments.
Total costs excluding shipping and including one of their MLS Gaskets is $665.00. Typical turnaround is 2 days. If you do not want their Gasket, cost is $ 550.00 + shipping. This includes surfacing and or lapping. Heads which do not need surfacing will be lapped to ensure flatness.
If the Heads are O ringed and need to be surfaced, there is an extra cost to recut the O ring depth. I was told with the new style Gasket, O ringing is un necessary.
Any questions, you should call Performance Developments. 949 646 7461. I may have missed something here.
The Flow numbers were done on Performance Developments SF600 Flow Bench @ 25" H2O, every 0.05" on a Stock Head with no other work, but a Multi angle/ radius Valve job. The original Valve seats were the standard 3 angles, touched up and pulled over 0.7b vacuum on their Serdi.
BTW, I asked today about the different test pressures. I was told that the Superflow Flow 600 benches are calibrated at 25" of water, and there is no correction factors required.
Stock angles PD Multi Radius Stock PD Multi Radius
IN IN EX EX
23.1 29.8 19.9 24.7
47.0 56.0 44.6 55.1
77.7 87.8 70.6 86.2
105.8 116.3 93.8 109.0
133.7 143.6 105.8 116.8
147.6 161.3 121.7 134.6
162.3 174.2 132.9 144.8
171.0 187.2 143.8 157.2
178.7 196.8 149.4 163.6
186.7 202.9 151.2 166.8
The lifts as measured are 0.472 In and 0.437 EX. The last row of numbers on the Intake are beyond the max stock lift, and the last 2 rows on the exhaust are beyond the max stock lift. They just show the flow potential.
It has been stated many time before that the new style multi angles/radius seats work better than the old style 3 angles. PD will not tell me the angles/ radi's and number of them used, nor any other little tricks to help with the flow.
I did ask PD what their typical cost to do a Head complete is. This is how they do it. You call them and they will UPS a shipping box to you to put the Head in. This saves you time and the box is made just for that Head. It even comes addressed back to Performance Developments.
Total costs excluding shipping and including one of their MLS Gaskets is $665.00. Typical turnaround is 2 days. If you do not want their Gasket, cost is $ 550.00 + shipping. This includes surfacing and or lapping. Heads which do not need surfacing will be lapped to ensure flatness.
If the Heads are O ringed and need to be surfaced, there is an extra cost to recut the O ring depth. I was told with the new style Gasket, O ringing is un necessary.
Any questions, you should call Performance Developments. 949 646 7461. I may have missed something here.
10-21-2003, 12:48 AM
#3
Rennlist Junkie Forever
Great info.
Although 15-18cfm average, is an definite improvement, it can't be compared to a 250-260cfm race port. Big difference.
And, $550 for a valve grind for a 15 - 18cfm improvement is on the expensive side considering that the intake manifold which is perfectly matched to the stock intake port is..... well... still stock.
That means that the 15-18cfm improvement won't be realized (on the intake side) without extensive port work to the intake manifold at a minimum.... and you can easily spend $1000-$1500 to port the factory intake or spend the same amount on an aftermarket intake (which I've yet to see proof that it betters a properly ported factory intake with the exception of the Milledge intake).
On the exhaust side, you have so much back pressure, the unless you are running a true Garrett turbine housing, you'll never realize the benefit there either.
But! For those of us running a real race head with the SFR header, big cam, and free flowing lower back pressure turbine housings... that 15 cfm is cheap HP!
I'm all over that!!!
I'll be calling them this week to see how they can better the Milledge race head I have.
Although 15-18cfm average, is an definite improvement, it can't be compared to a 250-260cfm race port. Big difference.
And, $550 for a valve grind for a 15 - 18cfm improvement is on the expensive side considering that the intake manifold which is perfectly matched to the stock intake port is..... well... still stock.
That means that the 15-18cfm improvement won't be realized (on the intake side) without extensive port work to the intake manifold at a minimum.... and you can easily spend $1000-$1500 to port the factory intake or spend the same amount on an aftermarket intake (which I've yet to see proof that it betters a properly ported factory intake with the exception of the Milledge intake).
On the exhaust side, you have so much back pressure, the unless you are running a true Garrett turbine housing, you'll never realize the benefit there either.
But! For those of us running a real race head with the SFR header, big cam, and free flowing lower back pressure turbine housings... that 15 cfm is cheap HP!
I'm all over that!!!
I'll be calling them this week to see how they can better the Milledge race head I have.
10-21-2003, 11:23 AM
#4
Remeber this is a standard Head rebuild, with NO porting. The gains are from good seat work only. If the flow across the seats is better, and you do no porting, your gains are thoe lost from inferior seat work. No majic here, just good repair work.
Now if you are talking porting. We were just comparing the differences to be had with the different seat angles.
For what you get, the cost is very reasonable. Remember, you get what you pay for. Seems to me, the lower price may pay for the lower Flow numbers .
Now if you are talking porting. We were just comparing the differences to be had with the different seat angles.
For what you get, the cost is very reasonable. Remember, you get what you pay for. Seems to me, the lower price may pay for the lower Flow numbers .
10-21-2003, 01:54 PM
#6
Race Car
Yeah I appreciate the info as well. It's hard to believe [at least for me] that valve seats/angles play such a big role in head flow. The head on my 944 will need to come off sometime soon [valve seals/guides] and I'll give these guys a call when it's ready. Thanks!
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10-21-2003, 07:52 PM
#8
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This seems a little odd to me it looks like the intake numbers are close to what Lindsey has on their site but the exhaust numbers are lower then what they have. I may just be reading this wrong or something but if anybody can shed some light on this for me I would appreciate it. I have no knowledge of this so I might be totally wrong here.
10-21-2003, 07:57 PM
#9
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When comparing head flow, make sure the flow bench is at the same pressure. (In the above scenareo 25").
Perhaps a good comparison will be between the above numbers and a head with new radius seats from another machinist. Usually seat work is in the $300 range..
Also, I would like to see how close (% wise) the above numbers are to ideal flow based on valve size..
Perhaps a good comparison will be between the above numbers and a head with new radius seats from another machinist. Usually seat work is in the $300 range..
Also, I would like to see how close (% wise) the above numbers are to ideal flow based on valve size..
10-21-2003, 10:29 PM
#10
After reading the questions here, I went back and asked for those who are interested.
All of the numbers I posted were results from flow testing at 25" H2O. I again asked why? I was told that the Performance Developemnts flow bench is a SuperFlow 600 which are all calibrated at 25" H2O. If you test at 28" or 36" H2O, there are correction factors which must be included, so as to equal out all numbers. If this is not done, then the flow numbers are incorrect. it was told to me, it would be like doing a dyno pull with different boost and then saying the HP is better.
I asked about the Lindsey numbers, Exhaust flowing more than the Intake, and they have never seen this on any 944 Heads they have flowed. I was also told that if the 944 Exhaust did flow more than the Intake, the stock Exhaust Valve could be smaller and have no effect on performance. This is NOT the case here.
I have no pausable reason why they post such numbers, when clearly they are not typical for a stock head.
The numbers posted by me were stock ports, unported, with just a really good Valve job. The difference is quite odd. PD's exhaust flow is lower, and their Intake is higher, the % difference what you would expect between Intake and Exhaust, but PD's are all numbers done @ 25" H2O. I suppose you take your pick who's numbers you want to accept as been accurate, and hope that the results show up on the dyno.
Now if we compare ported heads, this will really get interesting. My $ on the numbers I posted.
All of the numbers I posted were results from flow testing at 25" H2O. I again asked why? I was told that the Performance Developemnts flow bench is a SuperFlow 600 which are all calibrated at 25" H2O. If you test at 28" or 36" H2O, there are correction factors which must be included, so as to equal out all numbers. If this is not done, then the flow numbers are incorrect. it was told to me, it would be like doing a dyno pull with different boost and then saying the HP is better.
I asked about the Lindsey numbers, Exhaust flowing more than the Intake, and they have never seen this on any 944 Heads they have flowed. I was also told that if the 944 Exhaust did flow more than the Intake, the stock Exhaust Valve could be smaller and have no effect on performance. This is NOT the case here.
I have no pausable reason why they post such numbers, when clearly they are not typical for a stock head.
The numbers posted by me were stock ports, unported, with just a really good Valve job. The difference is quite odd. PD's exhaust flow is lower, and their Intake is higher, the % difference what you would expect between Intake and Exhaust, but PD's are all numbers done @ 25" H2O. I suppose you take your pick who's numbers you want to accept as been accurate, and hope that the results show up on the dyno.
Now if we compare ported heads, this will really get interesting. My $ on the numbers I posted.
10-25-2003, 01:29 AM
#11
Rennlist Junkie Forever
Silverbullet951
The point I made is that you can increase the intake port flow 15-18cfm, but since the stock intake manifold flows almost exactly what a stock intake port flows, the 15-18cfm increase on the intake port will not be realized in the form of any additional performance since the intake port, once bolted to the intake manifold, becomes one.
Therefore if the intake manifold is stock, the intake port isn't going to flow more, no matter what you do to it, once the intake manifold is bolted up to it, if the intake manifold is stock.
On the exhaust side... you are probably running at least 35psi-40psi back pressure with a KKK style turbine housing. Adding 15 cfm to the exhaust port isn't going to do much if anything at all.
Therefore, and like I said before, $550-$600 for a valve grind is probably not worth it for a car with a stock intake manifold, and a stock exhaust manifold/KKK style turbine housing.
That said, you can get a regular valve grind for less than 1/2 the above mentioned cost, and get the same to-the-wheels performance on a stock engine (stock intake, stock exhaust/cross over/KKK turbine).
The point I made is that you can increase the intake port flow 15-18cfm, but since the stock intake manifold flows almost exactly what a stock intake port flows, the 15-18cfm increase on the intake port will not be realized in the form of any additional performance since the intake port, once bolted to the intake manifold, becomes one.
Therefore if the intake manifold is stock, the intake port isn't going to flow more, no matter what you do to it, once the intake manifold is bolted up to it, if the intake manifold is stock.
On the exhaust side... you are probably running at least 35psi-40psi back pressure with a KKK style turbine housing. Adding 15 cfm to the exhaust port isn't going to do much if anything at all.
Therefore, and like I said before, $550-$600 for a valve grind is probably not worth it for a car with a stock intake manifold, and a stock exhaust manifold/KKK style turbine housing.
That said, you can get a regular valve grind for less than 1/2 the above mentioned cost, and get the same to-the-wheels performance on a stock engine (stock intake, stock exhaust/cross over/KKK turbine).
10-25-2003, 06:14 AM
#12
Actually Tony you are quite wrong about your theory. I had the Intake manifold flowed and each runner was measured for flow, the difference measured, the velocities, and the overall. We have a really good idea now how it flows and where to make some improvements. A very simple change inside made a substainial increase in flow.
And if you have forgotten that not all the Intakes Valves are open at the same time. This then allows the manifold to flow way more than the ports do. The stock manifold flows way more than the choke limit of the Intake port. You also need to understand that whatever the port does flow, it can flow more when the air can attach its self to more surface. The Performance Developments Flow bench has smoke attachment that shows how the air moves around the Valve, Vlave boss etc. The multi angle shapes rally do make a difference.
Its very easy to get caught in the trap of thinking that the manifold does not flow well, but it still flows way more than the ports do. Port a head, bolt on the stock manifold and see if the engine responds. Our testing has shown alot of interesting information. The stock manifold looks like it will be able to be used with some internal modifications. This then will allow most to use their existing manifold if they wish. The mods will be offered. We did flow a borrowed manifold from another vendor as a comparision, I will not say which one, and it flow better at the lower throttle angles up to approx 22%, but at after any more and especially WOT, the flow dropped off dramatically. Something very interesting, the manifold is made of fabricated aluminum, and when the higher throttle angles were opened the heat generated within the manifold could be felt on the outside. This is caused from poor flow and increased friction.
More tests are scheduled with the stock manifold after some more modifications, so I will try to post more updates.
As for the cost of the head work, I asked about this too. I was told that a proper Cylinder Head recondition should take just over 8 hours work, which can costs upwards or $ 800.00. If you want to pay less, go to a production machine shop and pay the $ 250- 300 amount. You get what you pay for. Do they check everything? Not at that price. Do they measure the guide clearances, Valve stem dia's , Valve runouts, Seat heights, measure and check the springs for spring rates, seat pressures, coil bind distance etc. Most, if not all do not. Remember, the 944 heads need to be very accurate with Valve seat heights, or the tappet goes into oil lock. For those who do not know what this is, the tappet is compressed almost or at times completely. When the valve spring decompresses the tappet cannot recover as fast. results are tappet wear, camlobe wear, and loss of power. Its like having a completely different camshaft in the engine. The valve closes at the wrong time, the overlap function changes, everything changes. Some of you may be experiencing this, not know it, and giving away Torque and HP. The head looked good, but does it perform the way it should. All the performance of an engine is from the head. Don't cheap out on the important areas. Spend more on the head and less on the frills.
And if you have forgotten that not all the Intakes Valves are open at the same time. This then allows the manifold to flow way more than the ports do. The stock manifold flows way more than the choke limit of the Intake port. You also need to understand that whatever the port does flow, it can flow more when the air can attach its self to more surface. The Performance Developments Flow bench has smoke attachment that shows how the air moves around the Valve, Vlave boss etc. The multi angle shapes rally do make a difference.
Its very easy to get caught in the trap of thinking that the manifold does not flow well, but it still flows way more than the ports do. Port a head, bolt on the stock manifold and see if the engine responds. Our testing has shown alot of interesting information. The stock manifold looks like it will be able to be used with some internal modifications. This then will allow most to use their existing manifold if they wish. The mods will be offered. We did flow a borrowed manifold from another vendor as a comparision, I will not say which one, and it flow better at the lower throttle angles up to approx 22%, but at after any more and especially WOT, the flow dropped off dramatically. Something very interesting, the manifold is made of fabricated aluminum, and when the higher throttle angles were opened the heat generated within the manifold could be felt on the outside. This is caused from poor flow and increased friction.
More tests are scheduled with the stock manifold after some more modifications, so I will try to post more updates.
As for the cost of the head work, I asked about this too. I was told that a proper Cylinder Head recondition should take just over 8 hours work, which can costs upwards or $ 800.00. If you want to pay less, go to a production machine shop and pay the $ 250- 300 amount. You get what you pay for. Do they check everything? Not at that price. Do they measure the guide clearances, Valve stem dia's , Valve runouts, Seat heights, measure and check the springs for spring rates, seat pressures, coil bind distance etc. Most, if not all do not. Remember, the 944 heads need to be very accurate with Valve seat heights, or the tappet goes into oil lock. For those who do not know what this is, the tappet is compressed almost or at times completely. When the valve spring decompresses the tappet cannot recover as fast. results are tappet wear, camlobe wear, and loss of power. Its like having a completely different camshaft in the engine. The valve closes at the wrong time, the overlap function changes, everything changes. Some of you may be experiencing this, not know it, and giving away Torque and HP. The head looked good, but does it perform the way it should. All the performance of an engine is from the head. Don't cheap out on the important areas. Spend more on the head and less on the frills.
10-25-2003, 10:30 AM
#13
Racer
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m42racer
Thank-you for all your research and objective comments. Please keep them coming. I am curious about the o-ring, how much hp can be gained with porting, and more about intake head and exhaust. Are you suggesting that it better to modify our stock manifold? Thanks in advance. ed
Thank-you for all your research and objective comments. Please keep them coming. I am curious about the o-ring, how much hp can be gained with porting, and more about intake head and exhaust. Are you suggesting that it better to modify our stock manifold? Thanks in advance. ed
10-25-2003, 11:15 AM
#14
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That said, you can get a regular valve grind for less than 1/2 the above mentioned cost, and get the same to-the-wheels performance on a stock engine (stock intake, stock exhaust/cross over/KKK turbine).
10-25-2003, 01:10 PM
#15
Good point Russ.
Something I always remember from been told a long time ago. Be wary of engine work from those who sell suspension amd the likes. If they are really good at something, they normally do not have to supplement with other parts and services.
Ask if they do it all in house, or shop it out. That makes a HUGE difference.
Something I always remember from been told a long time ago. Be wary of engine work from those who sell suspension amd the likes. If they are really good at something, they normally do not have to supplement with other parts and services.
Ask if they do it all in house, or shop it out. That makes a HUGE difference.