I wish there were more interests in alternative intake manifolds in both the LTx and B-Body Community. We could definetly use a much longer intake runner to get more low and midrange torque out of motors. Sorry 3" from plenum to intake port is NOT the way to go to produce decent torque numbers. I think the LT1 produces a nice flat torque curve and good torque numbers inspite of itself and its intake not because of it.

So in your opinion what is the best and cost effective intake on the aftermarket, short of fabbing up a sheetmetal intake to put on a LTx motor for a high performance street Impala SS/Caprice?? Stealthram? GMPP Ram Jet 350 intake manifold?? A converted single plane carb intake??? Or even Edelbrock's new Pro-Flo XT??

In my research people on the forums mentioned something about "cutting and welding" the stock LT1 intake but they did explained what that meant. Can you please enlighten me of what that entails and is it worth the effort???

 

Some people have enlarged the plenum volume of the intake by raising the top of the manifold (cutting and welding), in the belief that the stock plenum volume is inadequate for large air consumers like big displacement and/or high RPM.

 

Please let me know if i'm wrong, but i believe a stock lt1 intake is very hard to beat. it flows very well. I don't know about worth while porting without major cutting.

 

It flows well, but the point the OP is making is that a short runner (3") favors high RPM torque. Compare the LT1 manifold to the L98 manifold. The longer runners on the L98 (21") favor low end torque, and that's why the L98 makes more low end torque than the LT1. But the long runners help choke air flow at high RPM, leaving the L98 gasping for air above 5,000RPM.

The LS1 compromises with a 10" runner length. But the LS torque curve is very similar to the LT1 torque curve at low RPM, so the OP is correct - the LT1 intake produces a flat torque curve in spite of itself. There's a decent explanation in the SAE paper issued in 1992 to announce the development of the LT1 engine.

The LT5 had the best of both worlds, with two runners for each cylinder, one longer and one shorter. Then engine runs on only the long runners at low RPM. The shorter runners are opened up by 8 "secondary" throttle blades, so that at WOT/high RPM the engine is pulling air through both runners.

 

my mistake with reading, I'm tired when i get home from work, lol. As far as i know, the lt5 intake won't fit an lt1 anytime soon, but it is cool though. How about getting fancy with a nice dual plane carb intake with a fuel injection set up? you can set it up where you can still run all of the same sensors, injectors, accessories and computer.

 

Several years ago I modified a holley stealthram to work on my lt1. I was running a cam that was too big at the time due to a vender sending me the wrong one. the car went from a relatively soft bottom end to being able to smoke the tires from about a 30mph roll. it was all done by 6k though, so there is always a trade off.
Hope this helps.
Kory

 

I was not suggesting that the LT5 manifold would fit, any more than I was suggesting that an L98 or an LS1 manifold would fit (I mentioned all of them). I was simply pointing out the end results of real world applications used on various GM/Chevrolet engines.

 

Here is the manifold I built a few weeks ago. It was an Edelbrock Pro Ram II, now it fits my LT4 engine. Haven't swapped intakes yet, but will in a few months. More picture can be seen, follow the link in my sig.

 

sorry injuneer, just giving you flack. i understand where your coming from. but what do you think about my question? have a nice dual plane carb manifold with a throttle body and all the necessary sensors and accesories and injectors, and run it with a nice ported head and a truck cam and headers. the op asked about more low end power right?

 

Everything here seems to point to the low end of the power-range. That's all fine and dandy, but I see most of the down-fall to be the upper ranges. Everyone wants to rev them, and that would be the issue I see (also explains what Injuneer was saying about the cutting of the plenum). The idea behind the tunnel-ram is great, but the only problem I have with the given example is the plenum size. I'm sure it'll boost low-end numbers dramatically, but it looks to me like it may starve. I guess it all depends on what the engine has in it (ie. cam, heads, and rotating assembly) as to what intake design you would need. Kiinda the same as the Gen I sbc. Dual planes do great on the street where as the single planes work great on the drag strip. I see the LT1 manifold as more of the single plane, it just needs a little more plenum. That would be why it does so well in the mid and upper ranges......

Just my $.02

 

isn't that a bit much?

 

It depends on what you want. It sure isn't something for a stock 350ci. We'll see the difference in a couple of months between a ported LT4 intake and my conversion.

 

Are those runners "siamesed", or is there a dividing wall between adjacent cylinders?

 

it kills me to ask this question.. what do your heads flow and who ported them?

 

There is a wall between the adjacent cylinders. The runners are shaped real awkward. Going down from the inside of the plenum they are tapered to about 1 1/2" length, then go straight down about 1" without a taper, then 3 1/2" length tapered to the end.

Supposed to make real good TQ and HP up to about 8000 rpm. I shift at about 6700 rpm. As long as I don't loose any HP it will be okay, otherwise I'll use my LT4 intake again.