A couple of people have swapped intakes and said it made considerable gains. However, I have talked to several different people who have made good power with the truck intake. A guy from Thunder Racing said that the intakes make good power but, are rpm limited. He said that the truck intake will support a 408, as long as the rpms stay low. Chris at AP Engineering said qoute "Here is what I can tell you. I built two 427 engines for a marine application and they made 600 horse at the fly wheel with the truck intake and pulled up to 6800 rpm."
Now, listening to everyone and from my small amount of experience. The truck intake will make good power but is limited. I think that a low and midrange rpms the truck intake is perfect for a heavy, torque sucking truck. Now, if you want to spin above 6,200 you should have a stall and a car intake. I also think that with the truck intake, camshafts should have a single pattern or close to it, maybe even a reverse split. This would be the way to go NA or even a small amount of juice. However, boost or a large amount of jug would change that.
This is my opinion. What are your opinions?


P.S. I hope this gets as many responses as my blower discussion. I learned alot.

 

It just seems to me that the truck intake would crap-out at high rpms, considering what they look like on the inside. I've changed my opinion on the truck intakes after seeing BigTex's post, it just seems to me that the LS1/LS6 intake would be a big improvement over the restrictive design of the truck intakes. But, I really don't know enough about them I guess. That's just my opinion though

 

I think you are on the right track. At low rpms (low air flow), the truck intake would be fine. But when you really need more air flow, its got to be a restriction. Having a truck intake flowed on a flow bench isn't going to give much data, because a single runner would'n't tax the system. But when you have all 8 runners pulling through that internal chamber, I think flow would be hindered.

GM didn't build these trucks to go fast. They built them to be reliable and pull trailers. At part throttle / low rpms, the truck intake would probably make more torque. At WOT, the LS6 would more than likely be a better choice.

 

The "flow" of the intake is very good. It is the runner length everyone is fighting. It is like comparing a TPI motor to a LT1. There are TPI motors out there making good power and moster torque but, it is all low rpms.
Do trucks really need to spin that high of rpms to make good power. I think that the problem is not with the intakes but, with the camshaft selection that we are forced to chose from. All Gen III smallblock cams are designed for cars. When you call Comp or other companies the will give you one of their camshafts and say it will make good torque but, they are still designed for cars. How many camshafts out there don't peak until 6200 to 6300 or make power until 6,700 to 6,800. I think that is right where the truck intake starts to fall behind, due to the huge runner length.
The intake does not have a flow problem but a rpm problem.

 

Take a look at the runner length of both the truck intake and the LS6. You'll find that they are almost identical. We aren't fighting runner length.

You can have a cam ground to whatever specs you want. I don't think you will find a magic truck cam that will make 400 rwhp at 5500 rpms. If you did, the car guys would already be running it.

I do agree that its an rpm problem, but that is due to the higher flow needed to supply air.

 

I'm wondering if the worries about the truck intake are a lot like the whole "I get better mileage with my tailgate down" thing. (which I don't buy)

There is that pocket of possibly stagnant air at the back of the intake..... But there's also that pocket of stagnant air behind our cabs that pools up in the bed and alows the air to smoothly flow over the tailgate.

Anyone smell what I'm stepping in? It's a little hard to explain...

 

Also... any chance that pocket is a heimholtz resonator?

 

Well I will tell you guys what I find out I am changing my truck one in a week to a ls1... I have a totaly stock 5.7 in the truck so this should be interesting.

 

I had a conversation with one of the editors of Chevy High Performance last week, while he was at the shop and he advised me that they just did a intake shootout comparing the LSX,LS6,Truck Manifold,LS1,Holley,etc...

He advised me that the LSX won hands down in every area (Cam car/bolt-on car)

He went on to say that the truck manifold got second place overall and it's only fault was when spinning above 6200 rpms(This is when the LS6 started to shine)

Bottom line is the truck manifold is damm good unless you have done a cam and valvetrain upgrade and are spinning above 6000 rpms.

Brandin
Magnaflow Exhaust

 

That sounds REALLY interesting. Will they be running an article on that? I've read in another mag. that the LSX intake is an awesome design. It also allows pretty extensive porting, which would help bigger displacement applications and high reving engines.

Does anyone actually know the real runner lengths for any of these manifolds? If we have that, we can use one of those runner length equations to see if the truck manifold is actually adequate above a given RPM.

I feel that any intake where you gain hp, and don't lose any tq is a win-win situation. But if you lose tq and gain hp, you lose, especially with a heavy truck. Rarely will you gain in both areas though. Just my thoughts.