New! Edelbrock LS XT Intake Manifold
12-09-2008, 10:03 AM
#81
Back in my NA 5.0L days, I always heard that long runners = torque and short runners = hp. Similarly, small plenum = torque and large plenum = hp. I no longer think these "rules" are quite accurate as blanket statements (although they likely were for the 5.0L NA engines).
What is really cool about this mani in my thinking is that is a LARGE plenum, short runner manifold. The general rule of thumb for a V8 is that the plenum needs to be 1/2 the volume of the cylinder. A larger plenum slows down the intake charge, making more pressure (and denser charge to the cylinder). The trade off (for NA) is weaker throttle response, and low end power. Short runners means higher velocity between the plenum and the valve.
WildeRacing found a metric *** load of theory and posted it in the intake mani hard data thread.
https://www.performancetrucks.net/fo...1&postcount=38
https://www.performancetrucks.net/fo...6&postcount=39
https://www.performancetrucks.net/fo...0&postcount=41
Personally, I also like this manifold BECAUSE it's aluminum. There are a lot of tricksy things a guy can do with an aluminum manifold in a drag racing setting that can't be done with a plastic one.
What is really cool about this mani in my thinking is that is a LARGE plenum, short runner manifold. The general rule of thumb for a V8 is that the plenum needs to be 1/2 the volume of the cylinder. A larger plenum slows down the intake charge, making more pressure (and denser charge to the cylinder). The trade off (for NA) is weaker throttle response, and low end power. Short runners means higher velocity between the plenum and the valve.
WildeRacing found a metric *** load of theory and posted it in the intake mani hard data thread.
https://www.performancetrucks.net/fo...1&postcount=38
https://www.performancetrucks.net/fo...6&postcount=39
https://www.performancetrucks.net/fo...0&postcount=41
Personally, I also like this manifold BECAUSE it's aluminum. There are a lot of tricksy things a guy can do with an aluminum manifold in a drag racing setting that can't be done with a plastic one.
12-09-2008, 11:49 AM
#82
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This edelbrock intake looks very interesting indeed.
Tunnel rams got a bad name back in the carb days due to over carbeuration, which makes for sloppy throttle response and poor low rpm torque. Too much carb causes low velocity through teh intake, which helps fuel to fall out of suspension, coating the walls of the.
My Uncle had a 1969 Dodge Charger 500(1 of 24 with Hemi/4 speed), with a 426 hemi engine with a tunnel ram and dual 1350 cfm modified Dominators, even with 13.5:1 compression and methanol, it suffred with poor drivability. A swap to a single plane intake with a single 850cfm carb sure brought a bunch of drivability back. Of course the engine was down from its previous 850hp dyno rating, but the car was much more fun to drive. He swapped everything back to stock as he restored the car, then he sold it for a low super low mileage Ferarri Testarossa.
Big carbs are 1 thing, EFI is another.
I thought I would post this schematic of a Mercruiser Scorpion tunnel ram intake that has been used in Vortec L31 and conventional intake port/bolt patterns since the late 80's in performance boat EFI applications on both 350's and 383's. Just thought some of you may not have seen it before.
http://www.mercruiserparts.com/Show_...And+Fuel+Rails
When talking about long or short and large and small runner cross section area, we must compare apples to apples.
A 10" runner with 2.25" cross section will probably make better low rpm torque than a 10" runner with a 4" cross section area, if all other variables remain constant.
It really all depends on what you are looking for from an intake. popular higher stall torque converters make the low rpm torque factor a moot point.
Also 1 persons definition of good low rpm torque, is another persons definition of crappy low rpm torque. Some many aspects of performance mods are subjective, based on a persons point of view.
I guess my point is that blanket statements dont really properly describe every different intake. If you have some intake with a 10" runner and make the runners larger, this will increase the rpm at which it is useful. MAking them smaller will lower that rpm, FOR THIS PARTICULAR INTAKE. This is where the blanket statements may work, if you change to a completeley different intake, you really cant use a blanket statement to compare this new intake to another.
And as always, any intake will work best when it is used as part of a well thought out matched combination.
Speaking hypothetically, I beleive that this new Edelbrock tunnel ram would supply more equal cylinder to cylinder filling than a Victor jr intake, based soley on the the equal length/shape of the intake runners..
This tunnel ram can be looked at as either a truck intake unwound with the runner pointing upwards, or a Victor Jr. intake with equal length runners.
Everytime you introduce a curve in an airpath resistance is increased. The tunnel ram is the best way to minimize this resistance.
Isnt the rule of thumb something like adding a 1 90º bend in tubing equivalent to adding 25 ft of pipe?
Just think of this rule of thumb when comparing intakes, as any front mounted t-bodied intake has at least 1 90º to get the air from a horizontal to vertical plane.
This Edelbrock tunnel ram would require some substantial VE tuning as compared to a stock intake, not that it would be any harder to tune, simply that its requirements would be different.
Sorry to blather on, but this intake is a really nice piece, I am certainly considering it on future GEN 3 engine projects. Discussion is always a good thing.
peace
Hog
Tunnel rams got a bad name back in the carb days due to over carbeuration, which makes for sloppy throttle response and poor low rpm torque. Too much carb causes low velocity through teh intake, which helps fuel to fall out of suspension, coating the walls of the.
My Uncle had a 1969 Dodge Charger 500(1 of 24 with Hemi/4 speed), with a 426 hemi engine with a tunnel ram and dual 1350 cfm modified Dominators, even with 13.5:1 compression and methanol, it suffred with poor drivability. A swap to a single plane intake with a single 850cfm carb sure brought a bunch of drivability back. Of course the engine was down from its previous 850hp dyno rating, but the car was much more fun to drive. He swapped everything back to stock as he restored the car, then he sold it for a low super low mileage Ferarri Testarossa.
Big carbs are 1 thing, EFI is another.
I thought I would post this schematic of a Mercruiser Scorpion tunnel ram intake that has been used in Vortec L31 and conventional intake port/bolt patterns since the late 80's in performance boat EFI applications on both 350's and 383's. Just thought some of you may not have seen it before.
http://www.mercruiserparts.com/Show_...And+Fuel+Rails
When talking about long or short and large and small runner cross section area, we must compare apples to apples.
A 10" runner with 2.25" cross section will probably make better low rpm torque than a 10" runner with a 4" cross section area, if all other variables remain constant.
It really all depends on what you are looking for from an intake. popular higher stall torque converters make the low rpm torque factor a moot point.
Also 1 persons definition of good low rpm torque, is another persons definition of crappy low rpm torque. Some many aspects of performance mods are subjective, based on a persons point of view.
I guess my point is that blanket statements dont really properly describe every different intake. If you have some intake with a 10" runner and make the runners larger, this will increase the rpm at which it is useful. MAking them smaller will lower that rpm, FOR THIS PARTICULAR INTAKE. This is where the blanket statements may work, if you change to a completeley different intake, you really cant use a blanket statement to compare this new intake to another.
And as always, any intake will work best when it is used as part of a well thought out matched combination.
Speaking hypothetically, I beleive that this new Edelbrock tunnel ram would supply more equal cylinder to cylinder filling than a Victor jr intake, based soley on the the equal length/shape of the intake runners..
This tunnel ram can be looked at as either a truck intake unwound with the runner pointing upwards, or a Victor Jr. intake with equal length runners.
Everytime you introduce a curve in an airpath resistance is increased. The tunnel ram is the best way to minimize this resistance.
Isnt the rule of thumb something like adding a 1 90º bend in tubing equivalent to adding 25 ft of pipe?
Just think of this rule of thumb when comparing intakes, as any front mounted t-bodied intake has at least 1 90º to get the air from a horizontal to vertical plane.
This Edelbrock tunnel ram would require some substantial VE tuning as compared to a stock intake, not that it would be any harder to tune, simply that its requirements would be different.
Sorry to blather on, but this intake is a really nice piece, I am certainly considering it on future GEN 3 engine projects. Discussion is always a good thing.
peace
Hog
Last edited by hog; 12-09-2008 at 11:59 AM.
12-15-2008, 09:47 PM
#83
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jegs now has it listed. $449 ships in 10-17 days
http://www.jegs.com/i/Edelbrock/350/7139/10002/-1
wish I knew what kind of fuel rails/ injectors we will need to make it work.
http://www.jegs.com/i/Edelbrock/350/7139/10002/-1
wish I knew what kind of fuel rails/ injectors we will need to make it work.
12-16-2008, 03:16 PM
#87
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jegs now has it listed. $449 ships in 10-17 days
http://www.jegs.com/i/Edelbrock/350/7139/10002/-1
wish I knew what kind of fuel rails/ injectors we will need to make it work.
http://www.jegs.com/i/Edelbrock/350/7139/10002/-1
wish I knew what kind of fuel rails/ injectors we will need to make it work.
Dave
12-17-2008, 07:49 AM
#90
482 hp in an LS1 with that mild of a cam is pretty impressive. Cam wasn't much bigger than an LS6 cam. Says something for the heads too, I guess. I'd like to see someone, shall we say, a little more independent do the testing before I get too excited.