Yet another Intake Manifold Thread
05-06-2007, 07:42 AM
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Originally Posted by .T.
Mad props to Steve for posting these tests!
It's also very important to remember the weight of the truck when considering this information. Most of the trucks around here are DD's, while there's alot of overlapping information more beneficial true perfomance builds.
Using 425lb/ft as a reference, notice as the cam becomes larger it takes longer to cross that threshold. Basically, using a larger cam with a better flowing intake will create more power which isn't necessarily advantageous for moving the weight of the truck where it normally rolls.
With FI it may not present a problem on the street but I think that NA trucks should really keep an eye out to not over-size their cams. Their only real useful remedy without major tuning hassles would be to match it up with the right (high) stall converter.
Steve, thanks again for the graphs. Now, I know for sure I'll be sticking with my 210-218@116, idleing at 600rpm, with my truck intake. Spray on the way!
It's also very important to remember the weight of the truck when considering this information. Most of the trucks around here are DD's, while there's alot of overlapping information more beneficial true perfomance builds.
Using 425lb/ft as a reference, notice as the cam becomes larger it takes longer to cross that threshold. Basically, using a larger cam with a better flowing intake will create more power which isn't necessarily advantageous for moving the weight of the truck where it normally rolls.
With FI it may not present a problem on the street but I think that NA trucks should really keep an eye out to not over-size their cams. Their only real useful remedy without major tuning hassles would be to match it up with the right (high) stall converter.
Steve, thanks again for the graphs. Now, I know for sure I'll be sticking with my 210-218@116, idleing at 600rpm, with my truck intake. Spray on the way!
If anything I'd your post makes a better case against overcamming an engine than using the truck intake for a performance application. To me those graphs show almost identical torque curves, but with much better high end with the LS6 or FAST intake. If you could do a mod that would give you some more high end hp and give up just a few or even no lb-ft of torque, then why wouldn't you do it?
IMO, people here over cam engines all the time and lose big time low end and mid range and complain about laziness off the line until they install 3500 rpm converters, and that is perfectly acceptable, yet everyone is scared of the big "low end loss" from a car intake.
Steve, could you post the actual numerical data from these tests so we can quantify just how much is gained or lost?
05-06-2007, 01:23 PM
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Tdrumm, I'm sure we're on the same page here. So, "Why won't 'I' do it"?
HP:
The truck intake is not ideal for a true high performance application due to it's degrading flow at high rpm=less power. This is examplified in Steve's 3rd table chart w/281 cam (Truck vs Fast) where it begins to drop off behind the Fast's HP @4800rpm. In that test the peak HP gain is just 18HP@6400prm for the Fast.
But, IMHO, the gain of 18HP at peak with the Fast isn't worth the time and cost of the intake swap. Especially when you consider all the peripheral mods that go along with the swap, like the waterpump, rails, etc and that these results were measured at the crank!
TQ:
And yes, I also believe that someone using this info to plan their build, should take note that the increase in cam size requires more deliberate tuning and a higher stall converter in order to bring the heavy truck into it's peak torque range even with the truck intake.
Furthermore, the smaller, easier-to-tune, stock converter cam is putting out more usable torque from 3000-5000prm in the 265cam graph. In reality, this is the range where the heavy weight truck benefits from that torque the most. So, perhaps it makes sense to choose a cam that is easy to tune, doesn't require a converter swap, puts out gobs of usable torque and still allows the truck to be a truck and tow/haul when it needs to. Then, there's the option of a higher stall for launching harder.
I see by your sig that you're looking at a similar cam to mine but I'm not sure which.
Although my NA build is damn strong, it's one of those which HP flatlines (not "nosedives") @5000rpm because of the truck intake (link to graph). The original plan was to stay NA and put up as much HP as possible which almost had me ready to go for the swap. Now, plan 'B', nitrous on the way thanks to research like this... atleast until a tight, plug-n-play, swap kit hits the market for reasonable money... I'll spray for HP, thanks. And, even that will allow me to continue working on the NA build.
HP:
The truck intake is not ideal for a true high performance application due to it's degrading flow at high rpm=less power. This is examplified in Steve's 3rd table chart w/281 cam (Truck vs Fast) where it begins to drop off behind the Fast's HP @4800rpm. In that test the peak HP gain is just 18HP@6400prm for the Fast.
But, IMHO, the gain of 18HP at peak with the Fast isn't worth the time and cost of the intake swap. Especially when you consider all the peripheral mods that go along with the swap, like the waterpump, rails, etc and that these results were measured at the crank!
TQ:
And yes, I also believe that someone using this info to plan their build, should take note that the increase in cam size requires more deliberate tuning and a higher stall converter in order to bring the heavy truck into it's peak torque range even with the truck intake.
Furthermore, the smaller, easier-to-tune, stock converter cam is putting out more usable torque from 3000-5000prm in the 265cam graph. In reality, this is the range where the heavy weight truck benefits from that torque the most. So, perhaps it makes sense to choose a cam that is easy to tune, doesn't require a converter swap, puts out gobs of usable torque and still allows the truck to be a truck and tow/haul when it needs to. Then, there's the option of a higher stall for launching harder.
I see by your sig that you're looking at a similar cam to mine but I'm not sure which.
Although my NA build is damn strong, it's one of those which HP flatlines (not "nosedives") @5000rpm because of the truck intake (link to graph). The original plan was to stay NA and put up as much HP as possible which almost had me ready to go for the swap. Now, plan 'B', nitrous on the way thanks to research like this... atleast until a tight, plug-n-play, swap kit hits the market for reasonable money... I'll spray for HP, thanks. And, even that will allow me to continue working on the NA build.
Last edited by .T.; 05-06-2007 at 01:46 PM.
01-14-2008, 09:51 PM
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so far im liking my 85mm pro-prod intake..gonna go back to the dyno soon and see what it does with the 85mm TB and 4in cold air i made instead of my k&n that necked down to 60mm
01-14-2008, 11:24 PM
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http://www.professional-products.com...oldsLS1LS2.php
$370 on ebay all day long and it comes with rails, fittings and lines..get 85mm or 96mm
$370 on ebay all day long and it comes with rails, fittings and lines..get 85mm or 96mm
