Flow numbers for DIY intake vs stock, & LE2 head
01-17-2007, 07:50 PM
#1
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Flow numbers for DIY intake vs stock, & LE2 head
I port matched the stock LT1 intake to my LE2 heads using templates I made using the head ports. Pretty typical intake mods, mostly. I'm not set up to post pics so I'll just describe what I changed, then give the flow data for your feedback.
I added dowel pins to control the alignment between the intake and heads, after mocking up the planned deck height and gasket thickness. Then I opened it to 58mm at TB and removed all the bolt bumps inside the intake, including the ones just before the runners. I cut the roof of each port down to the edge of the injector hole, and blended all the transitions. Also smoothed & polished the cast finish everywhere I could reach, especially the radii of the port entrances, the lead in to the runners, and the area immediately inside the TB holes.
One thing I did was probably a mistake, though. I added about 3/32 inch of taper to the width of each runner, by removing material from the common wall between each pair. This left those walls with a knife edge at the upstream end, which I have since learned can cause flow instability. A radiused leading edge would have been better. Live & learn. The flow bench guy said he was initially worried about that, but after flowing the parts and hearing the air move, he thinks it's ok. But I don't know if the air velocity at 28 inH2O is really high enough to show if I caused a problem.
Here are the intake numbers (CFM) for the bare head, head with stock intake, and head with ported intake. Last column is exhaust, head only. Conditions are 28 in H2O, corrected:
Lift.....Bare.....Stock.....Ported....Difference.. ..Exhaust
200....130.9....140.7.....139.8.....-0.9............106.8
250....165.6....167.3.....167.4.....+0.1.......... ..126.4
300....197.7....193.0.....197.5.....+4.5.......... ..141.6
350....224.4....210.3.....219.7.....+9.4.......... ..156.7
400....244.8....230.7.....235.4.....+4.7.......... ..167.4
450....260.5....241.7.....244.8.....+3.1.......... ..175.4
500....274.6....247.9.....254.2.....+6.3.......... ..185.2
550....280.9....254.2.....257.3.....+3.1.......... ..190.0
600....284.0....258.9.....260.5.....+1.6.......... ..193.6
650....289.4....257.3.....263.6.....+6.3.......... ..N/A
Lloyd's head flows are surprisingly nice, and the engine builder that flowed them was impressed. What can you guys tell me about my intake results? I like the mid-lift gains, and I'm relieved I didn't make the flow get worse. But I doubt this could equal a professional intake job. Also, after all the work, let me tell you all that Lloyd's price for porting is a bargain even if you could get the same performance yourself!
Any guestimates on HP gain for my intake port job? Maybe 4%, or about 16HP on an LE2 383?
I added dowel pins to control the alignment between the intake and heads, after mocking up the planned deck height and gasket thickness. Then I opened it to 58mm at TB and removed all the bolt bumps inside the intake, including the ones just before the runners. I cut the roof of each port down to the edge of the injector hole, and blended all the transitions. Also smoothed & polished the cast finish everywhere I could reach, especially the radii of the port entrances, the lead in to the runners, and the area immediately inside the TB holes.
One thing I did was probably a mistake, though. I added about 3/32 inch of taper to the width of each runner, by removing material from the common wall between each pair. This left those walls with a knife edge at the upstream end, which I have since learned can cause flow instability. A radiused leading edge would have been better. Live & learn. The flow bench guy said he was initially worried about that, but after flowing the parts and hearing the air move, he thinks it's ok. But I don't know if the air velocity at 28 inH2O is really high enough to show if I caused a problem.
Here are the intake numbers (CFM) for the bare head, head with stock intake, and head with ported intake. Last column is exhaust, head only. Conditions are 28 in H2O, corrected:
Lift.....Bare.....Stock.....Ported....Difference.. ..Exhaust
200....130.9....140.7.....139.8.....-0.9............106.8
250....165.6....167.3.....167.4.....+0.1.......... ..126.4
300....197.7....193.0.....197.5.....+4.5.......... ..141.6
350....224.4....210.3.....219.7.....+9.4.......... ..156.7
400....244.8....230.7.....235.4.....+4.7.......... ..167.4
450....260.5....241.7.....244.8.....+3.1.......... ..175.4
500....274.6....247.9.....254.2.....+6.3.......... ..185.2
550....280.9....254.2.....257.3.....+3.1.......... ..190.0
600....284.0....258.9.....260.5.....+1.6.......... ..193.6
650....289.4....257.3.....263.6.....+6.3.......... ..N/A
Lloyd's head flows are surprisingly nice, and the engine builder that flowed them was impressed. What can you guys tell me about my intake results? I like the mid-lift gains, and I'm relieved I didn't make the flow get worse. But I doubt this could equal a professional intake job. Also, after all the work, let me tell you all that Lloyd's price for porting is a bargain even if you could get the same performance yourself!
Any guestimates on HP gain for my intake port job? Maybe 4%, or about 16HP on an LE2 383?
01-18-2007, 05:23 AM
#3
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Join Date: Aug 2002
Location: Red Oak Texas
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I would also install the TB and then block off the other 7 cylinders at the iontake/head flange. Just use Duct tape on a gasket so you are not sucking air directly from ports across from you. This makes the air follow the path from TB to port and make the 90* turn .
Also make sure and have an inj. in the hole to keep air from coming in there.
Some of these gains can be seen on the flow bench at 28" and if you can keep raising depression until it goes turbulent with stock intake and then do the portwork so the port goes turbulent at a much later depression, you will gain power, even if there is no CFM gain.
Also make sure and have an inj. in the hole to keep air from coming in there.
Some of these gains can be seen on the flow bench at 28" and if you can keep raising depression until it goes turbulent with stock intake and then do the portwork so the port goes turbulent at a much later depression, you will gain power, even if there is no CFM gain.
01-18-2007, 08:10 PM
#5
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Well, I instructed the shop to plug the other 7 ports and injector holes. Do the numbers seem wrong for that? I'll confirm he did so.
TB is a good idea, but I don't know if I'll go back. $70 worth of info already.
Thanks for the feedback!
TB is a good idea, but I don't know if I'll go back. $70 worth of info already.
Thanks for the feedback!
01-20-2007, 10:59 AM
#9
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I'm glad you guys find this interesting. No, I don't think there are any easy ways to make a significant improvement.
I confirmed that the other 7 ports and all injector holes were plugged. EGR stuff was not. Data is for #5 cylinder.
As to what to do, everything I changed is outlined in my initial post. I wouldn't say any of this was 'Easy' but it was fun. It was relatively hard work hunching over the head for several hours, and I got yelled at a couple of times 'what's all this shiny dust you tracked into the house?'
I spent about $60 for a couple of nice carbide double-cut aluminum burrs (still like new), $30 in consumable abrasives, $70 to get the flow numbers, and at least 8 hours of time, so a $200 pro job that would have probably delivered at least twice the performance gain is very worthwhile. But, in many cases I would rather do something myself for fun, and to see how well I can accomplish it. Only $30 of the material cost is 'wasted', the burrs are nice to have and the flow data could have been ommitted. So if you think this kind of thing is fun and you don't mind the risk of low gains, why not give it a try? BTW I previously tried porting one of my Briggs minibike engines, including the valve area, and it is much WORSE after my work.
I won't presume to be able to tell anybody else what to do, since I didn't flow each step of the process to know which of the things I did helped vs hurt performance. For all I know, the larger TB hole is 90% of the gain. That was only about 2% of the work. I guess the most confident advice I could share is that the intake needs to be matched to the heads, not the gasket. And, get any un-necessary bumps and casting misalignment out of the air's way. Funny that 90% of the 'how to port' advice I found on the web was for gasket matching. The last thing you want is an intake runner that is bigger than the head port thus creating a 'step' in the surface.
Before starting, I had already decided to measure the results, and to have a used intake done professionally if the numbers improved minimally or got worse. As mentioned above, simply improving flow at a given depression does not guarantee more power. Same is true for head flows. I asked for flow data at 60inH2O and 100 inH2O, too, but the shops bench won't suck that hard. I'm a novice. I didn't know a lot of this myself before joining this board and learning who knows what they are doing, then reading their posts over and over to pick up the golden nuggets of info.
If you search 'intake port matching' and similar phrases, you will find the horsepower wizards around here have posted some intake porting advice several times, and you can find pictures here and on some of the websites that offer intake work for LT1's. Take a couple of days and read every LT1 post made by Nighttrain66, for example, and you will learn alot. Other names come to mind as well, but I won't try to list them. You don't need to be around here too long to figure out who knows their stuff.
I think it is way cooler and more satisfying to build something yourself and get average results, than to buy it perfect.
I confirmed that the other 7 ports and all injector holes were plugged. EGR stuff was not. Data is for #5 cylinder.
As to what to do, everything I changed is outlined in my initial post. I wouldn't say any of this was 'Easy' but it was fun. It was relatively hard work hunching over the head for several hours, and I got yelled at a couple of times 'what's all this shiny dust you tracked into the house?'
I spent about $60 for a couple of nice carbide double-cut aluminum burrs (still like new), $30 in consumable abrasives, $70 to get the flow numbers, and at least 8 hours of time, so a $200 pro job that would have probably delivered at least twice the performance gain is very worthwhile. But, in many cases I would rather do something myself for fun, and to see how well I can accomplish it. Only $30 of the material cost is 'wasted', the burrs are nice to have and the flow data could have been ommitted. So if you think this kind of thing is fun and you don't mind the risk of low gains, why not give it a try? BTW I previously tried porting one of my Briggs minibike engines, including the valve area, and it is much WORSE after my work.
I won't presume to be able to tell anybody else what to do, since I didn't flow each step of the process to know which of the things I did helped vs hurt performance. For all I know, the larger TB hole is 90% of the gain. That was only about 2% of the work. I guess the most confident advice I could share is that the intake needs to be matched to the heads, not the gasket. And, get any un-necessary bumps and casting misalignment out of the air's way. Funny that 90% of the 'how to port' advice I found on the web was for gasket matching. The last thing you want is an intake runner that is bigger than the head port thus creating a 'step' in the surface.
Before starting, I had already decided to measure the results, and to have a used intake done professionally if the numbers improved minimally or got worse. As mentioned above, simply improving flow at a given depression does not guarantee more power. Same is true for head flows. I asked for flow data at 60inH2O and 100 inH2O, too, but the shops bench won't suck that hard. I'm a novice. I didn't know a lot of this myself before joining this board and learning who knows what they are doing, then reading their posts over and over to pick up the golden nuggets of info.
If you search 'intake port matching' and similar phrases, you will find the horsepower wizards around here have posted some intake porting advice several times, and you can find pictures here and on some of the websites that offer intake work for LT1's. Take a couple of days and read every LT1 post made by Nighttrain66, for example, and you will learn alot. Other names come to mind as well, but I won't try to list them. You don't need to be around here too long to figure out who knows their stuff.
I think it is way cooler and more satisfying to build something yourself and get average results, than to buy it perfect.
01-20-2007, 11:38 AM
#10
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Location: Ocala, Florida
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01-20-2007, 07:02 PM
#11
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Join Date: Aug 2002
Location: Red Oak Texas
Posts: 1,509
You can probably knock that down to about 15-18 cfm loss with on of my ported intakes.
Like I mentioned, the CFM isn't really what you are after, you are really trying to open up the minimum cross section of the intake manifold to the same size as the minimum cross section of the intake port of the head.
The CFM test doesn't show how fast the air is moving in the head or intake and you would wanna make sure the intake doesn't restrict the flow (smaller cross section) compared to the intake port.
Once you get the measurement you want, then you can start helping flow (widen port at plenum area, correct angle that intake manifold port and cylinder head intake port connect, open up ALOT behind TB, etc) and gain CFM. Getting the measurements right to feed will show up at the track and dyno but might not show up on the flow bench @ 28".
I charge $200 to fully port the intake and I usuallyu remove about 2.5-3 lbs of aluminum from the intake.
Like I mentioned, the CFM isn't really what you are after, you are really trying to open up the minimum cross section of the intake manifold to the same size as the minimum cross section of the intake port of the head.
The CFM test doesn't show how fast the air is moving in the head or intake and you would wanna make sure the intake doesn't restrict the flow (smaller cross section) compared to the intake port.
Once you get the measurement you want, then you can start helping flow (widen port at plenum area, correct angle that intake manifold port and cylinder head intake port connect, open up ALOT behind TB, etc) and gain CFM. Getting the measurements right to feed will show up at the track and dyno but might not show up on the flow bench @ 28".
I charge $200 to fully port the intake and I usuallyu remove about 2.5-3 lbs of aluminum from the intake.
01-20-2007, 09:59 PM
#12
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Join Date: Mar 2002
Location: Ocala, Florida
Posts: 3,245
You can probably knock that down to about 15-18 cfm loss with on of my ported intakes.
Like I mentioned, the CFM isn't really what you are after, you are really trying to open up the minimum cross section of the intake manifold to the same size as the minimum cross section of the intake port of the head.
The CFM test doesn't show how fast the air is moving in the head or intake and you would wanna make sure the intake doesn't restrict the flow (smaller cross section) compared to the intake port.
Once you get the measurement you want, then you can start helping flow (widen port at plenum area, correct angle that intake manifold port and cylinder head intake port connect, open up ALOT behind TB, etc) and gain CFM. Getting the measurements right to feed will show up at the track and dyno but might not show up on the flow bench @ 28".
I charge $200 to fully port the intake and I usuallyu remove about 2.5-3 lbs of aluminum from the intake.
Like I mentioned, the CFM isn't really what you are after, you are really trying to open up the minimum cross section of the intake manifold to the same size as the minimum cross section of the intake port of the head.
The CFM test doesn't show how fast the air is moving in the head or intake and you would wanna make sure the intake doesn't restrict the flow (smaller cross section) compared to the intake port.
Once you get the measurement you want, then you can start helping flow (widen port at plenum area, correct angle that intake manifold port and cylinder head intake port connect, open up ALOT behind TB, etc) and gain CFM. Getting the measurements right to feed will show up at the track and dyno but might not show up on the flow bench @ 28".
I charge $200 to fully port the intake and I usuallyu remove about 2.5-3 lbs of aluminum from the intake.
I know thats a badass deal thats why I got one a few months ago.
I had no idea you removed ~3lbs of aluminum though, thats ALOT of material.
01-24-2007, 09:14 PM
#14
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Location: newton, kansas, USA
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I'm sure like anything else there is a much more complex answer that i'm missing but i'll ask my question anyways. So why would anyone buy LE2 heads, Ai heads, or any other ported heads that flow above 250-260ish? because the stock intake can't support anything more than that judging by the data given. It seems that very very few people with ported heads even get their intake ported. If the intake is only gonna flow 255-260ish it would seem having a head that flowed 270-280 is just wasted money and effort. Tell me what i'm missing please.
01-24-2007, 09:36 PM
#15
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Posts: 6,518
It's not all about the intake manifold flow.... there are many times, in fact almost every time you increase head flow CFM (if the quality of the flow is good) that you gain HP, reguardless if the head flows the same with the intake on.
This is especially true in a LS1 motor. A LS1 intake will flow 288cfm at best with a head, but putting a 320cfm head on the motor over a 290cfm head is up a big amount of power, 50hp or so. You can even have cases where you change the intake to increase flow but the power goes down.
Now if you head only flows 260cfm, even then a stock intake is a restriction. It's not going to be worth AS much power as a head with a 280cfm but it's worth something.
Engines are tricky things.
The best case is a head where it flows MORE with the intake on. I've seen motors flow 15 more CFM with a intake attached over a radius entry, now thats a good deal
Bret
This is especially true in a LS1 motor. A LS1 intake will flow 288cfm at best with a head, but putting a 320cfm head on the motor over a 290cfm head is up a big amount of power, 50hp or so. You can even have cases where you change the intake to increase flow but the power goes down.
Now if you head only flows 260cfm, even then a stock intake is a restriction. It's not going to be worth AS much power as a head with a 280cfm but it's worth something.
Engines are tricky things.
The best case is a head where it flows MORE with the intake on. I've seen motors flow 15 more CFM with a intake attached over a radius entry, now thats a good deal
Bret