Head Porting and Flow testing
Thread Starter
6th Gear
Joined: Apr 2003
Posts: 6
Likes: 0
From: State College PA
Head Porting and Flow testing
Hi. I am a new member to the Board. My brother and I do cylinder head porting and flow testing on small block Mopars. http://www.shadydellspeedshop.com We have only been doing this as a business for about 6 months, but have been keept very busy from members of an all Mopar board on the net.
I had an 87 ragtop that I had to sell about 2 years ago, and want to get back into Vettes. I know a lot about small block Mopar cylinder heads, but not small block chevys. We have our own flow bench, all the tools for porting and our own valve seat grinder.
I want to start my learning curve on L98 heads, either the earlier cast iron, or later aluminum. If anyone out there has L98 heads that they want flow tested ported, or even a single head laying around that they want to sell, send me an e-mail at dkj103@psu.edu
When I get my hands on an L98 head I will flow test as recieved, do some porting, and flow test again. I will post my results here so others may see, learn and disscuss.
Do you know if there are other active members on this board that have a flowbench and post results fequently?
Dave
I had an 87 ragtop that I had to sell about 2 years ago, and want to get back into Vettes. I know a lot about small block Mopar cylinder heads, but not small block chevys. We have our own flow bench, all the tools for porting and our own valve seat grinder.
I want to start my learning curve on L98 heads, either the earlier cast iron, or later aluminum. If anyone out there has L98 heads that they want flow tested ported, or even a single head laying around that they want to sell, send me an e-mail at dkj103@psu.edu
When I get my hands on an L98 head I will flow test as recieved, do some porting, and flow test again. I will post my results here so others may see, learn and disscuss.
Do you know if there are other active members on this board that have a flowbench and post results fequently?
Dave
Le Mans Master
Joined: Jul 2000
Posts: 7,634
Likes: 325
From: Greenville SC
Re: Head Porting and Flow testing (dkj103)
Cool. I would be interested in seeing what you could do on some LT1 heads. Do you use any CNC machines or is it all hand done? It looks like you are gettting a lot of extra flow at .5 and up, but not below that, why is that?
I don't think many people have their own flow bench.
I don't think many people have their own flow bench.
Thread Starter
6th Gear
Joined: Apr 2003
Posts: 6
Likes: 0
From: State College PA
Re: Head Porting and Flow testing (dkj103)
No CNC. Everything done by hand with a die grinder. Trick is to have the right carbide bits and sanding rolls. CNC porting is usually even more expensive that hand porting due to the fact that CNC machines can be upward of 100k and it takes a lot of time to program them for a specific head.
Typicaly porting won't help the low lift flow. Low lift flow is dominated by valve size and port geometry. Is it only when the air really gets moving that increase in bowl size, changing the shape of the short turn, opening up the pushrod pinch area really takes effect. Every head "stalls" or the flow separates at different lifts. Subtle changes in the shape of the short turn can help prolong this flow separation until higher lifts, where the cam would never see anyhow. It is kind of like an airplane wing.....you get to a certain angle of attack, and the wing will "stall" when the flow separates from the upper surface of the wing. You can actually hear the change when you have the head on the flowbench, as you increase the valve lift.
I would love to get an LT-1 head on my bench and see what it will do. E-mail me if you want to talk specifics.....
Dave
Typicaly porting won't help the low lift flow. Low lift flow is dominated by valve size and port geometry. Is it only when the air really gets moving that increase in bowl size, changing the shape of the short turn, opening up the pushrod pinch area really takes effect. Every head "stalls" or the flow separates at different lifts. Subtle changes in the shape of the short turn can help prolong this flow separation until higher lifts, where the cam would never see anyhow. It is kind of like an airplane wing.....you get to a certain angle of attack, and the wing will "stall" when the flow separates from the upper surface of the wing. You can actually hear the change when you have the head on the flowbench, as you increase the valve lift.
I would love to get an LT-1 head on my bench and see what it will do. E-mail me if you want to talk specifics.....
Dave
Drifting
Joined: Dec 2002
Posts: 1,861
Likes: 4
From: Houston TX
Re: Head Porting and Flow testing (dkj103)
First off, welcome to the board. Unfortunately, I have some technical questions which I hope you don't take as harsh. Just asking some in-depth tech questions.
Why are you flowing the heads at 10" H20? At that pressure drop, you will not see flow characteristics consistent with a running IC engine. Because of the lower air velocity, the flow will not separate at a valve lift indicative of actual engine operation. As such, it is VERY dangerous to convert flow numbers from a lower dP to a higher dP, as the conversion equation assumes the flow does not separate. That's why that conversion equation is used almost exclusively for converting flows at 28" H2O (industry standard) to 20.54" (the pressure drop associated with an average flow velocity of 300 ft/sec, which is the velocity that intake manifolds and camshafts are designed around. FWIW, I'm not just mouthing off. I do R&D for a top NASCAR program, including having 4 Winston Cup engines for dyno testing (including basic dyno testing, combustion analysis, etc, etc).
[Modified by CorvetteZ51Racer, 5:45 AM 4/4/2003]
Why are you flowing the heads at 10" H20? At that pressure drop, you will not see flow characteristics consistent with a running IC engine. Because of the lower air velocity, the flow will not separate at a valve lift indicative of actual engine operation. As such, it is VERY dangerous to convert flow numbers from a lower dP to a higher dP, as the conversion equation assumes the flow does not separate. That's why that conversion equation is used almost exclusively for converting flows at 28" H2O (industry standard) to 20.54" (the pressure drop associated with an average flow velocity of 300 ft/sec, which is the velocity that intake manifolds and camshafts are designed around. FWIW, I'm not just mouthing off. I do R&D for a top NASCAR program, including having 4 Winston Cup engines for dyno testing (including basic dyno testing, combustion analysis, etc, etc).
[Modified by CorvetteZ51Racer, 5:45 AM 4/4/2003]
Drifting
Joined: Feb 2003
Posts: 1,976
Likes: 2
From: San Antonio Texas
Re: Head Porting and Flow testing (dkj103)
:seeya Hello, and welcome to the forum. You'll find a lot of good info here. Looking forward to your in-put as well.
I do have to agree with CorvetteZ51Racer as I thought the industry standard was 28". Otherwise, comparison is really not possible IMHO.
:chevy
I do have to agree with CorvetteZ51Racer as I thought the industry standard was 28". Otherwise, comparison is really not possible IMHO.
:chevy
Drifting
Joined: Dec 2002
Posts: 1,861
Likes: 4
From: Houston TX
Re: Head Porting and Flow testing (Curveit)
:seeya Hello, and welcome to the forum. You'll find a lot of good info here. Looking forward to your in-put as well.
I do have to agree with CorvetteZ51Racer as I thought the industry standard was 28". Otherwise, comparison is really not possible IMHO.
:chevy
I do have to agree with CorvetteZ51Racer as I thought the industry standard was 28". Otherwise, comparison is really not possible IMHO.
:chevy
Thread Starter
6th Gear
Joined: Apr 2003
Posts: 6
Likes: 0
From: State College PA
Re: Head Porting and Flow testing (dkj103)
Z51
You have a good point. Testing at 28 inches is prefered over testing at 10 and correcting to 28 inches for the reasons you talked about. Problem being that, a Super flow 600 that can pull 28 inches of water cost $6000. I have to port a lot of cylinder heads before I can afford that.
But with, that said, there is still a lot to be learned from from a bench at 10 inches of water. I have had the same head on my bench and on a 28inch bench, and you get the same trend, but not nessesarly the exact same numbers. Also there is the issue of comparing numbers from one bench to another. Basically, I use my bench to see where I am at when I start, use it to look for flow, and get a good idea how much improvement I have made. But not get hung up over my peak numbers vs another bench's peak numbers.
Dave
You have a good point. Testing at 28 inches is prefered over testing at 10 and correcting to 28 inches for the reasons you talked about. Problem being that, a Super flow 600 that can pull 28 inches of water cost $6000. I have to port a lot of cylinder heads before I can afford that.
But with, that said, there is still a lot to be learned from from a bench at 10 inches of water. I have had the same head on my bench and on a 28inch bench, and you get the same trend, but not nessesarly the exact same numbers. Also there is the issue of comparing numbers from one bench to another. Basically, I use my bench to see where I am at when I start, use it to look for flow, and get a good idea how much improvement I have made. But not get hung up over my peak numbers vs another bench's peak numbers.
Dave
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