I am thinking about getting a new intake manifold pretty soon and can't decide between the Weiand/Lingenfelter 300-111P or the F.A.S.T. LSX.

Keep in mind that I probably will never use any type of forced induction on my car, my goal is to reach 500 RWHP N/A. Thanks for your help.

 

The Weiland/Liengefelter is pretty close to a stock LS6 manifold, just cast metal instead of plastic. You can polish it for a nice look and because it is metal you can pressurize it a lot, otherwise it has not advantage over the LS6, as I understand.

Call Lingenfelter and talk to to Ed Potter and I think he will tell you this also (he can sell you the Weiland or a FASt manifold: I got my FAST from him).

If you are going to go for 500 RWHP N/A, you will need to get something with a 90 mm throttle body: a FAST 90 mm version which means a good bit of money for the 90 mm throttle body, but you'll need it (the throttle body will cost as much or more than the manifold).

Data points:
My current 427 C5R engine before the SC, it had then (and has now) only 10:2 compression ratio and not-too-radical cam, but 427 cubic inches with fantastic heads (patriot III with custom porting, flowed 347): produced 485 RWHP @5800 with a stock LS6 manifold, 507 RWHP @ 6200 with the FAST, all normally aspirated.

The 408 in the Camaro (11.25:1, AFR big-port heads) is more dramatic difference. With an LS6 it produced only 465 RWHP at 5400. With a FAST 90 mm it did 512 at 6500. This engine was just starving for air and could not even get into the cam's power band with the LS6 manifold.

 

Now I was reading a description of the FAST manifold and it was saying that unless you are either using forced induction or a stroker that you should use the 78mm version. Based on that info I was going to go with the 78mm...with that being said you don't think the 90mm will be to much if I don't plan to stroke or bore the engine?

 

Well, my reply was based mostly on your wanting 500 RWHP. I don't think you will get that N/A through a 78 mm throttle body, and you will certainly get more power out of any heavily modded engine with the 90mm. I have not seen 500 RWHP through any stock or even slightly ported (there is some way folks open it up a mm or two which helps a little and someone else makes an 83 mm body, I hear).

that said, yes, FAST is right in their literature: the smaller tube manifold (which can use the stock throttle body) is not just adequate, but more appropriate for stock or lightly modified engines: but you won't get anyway near 500 RWHP from such an engine.

Given that you want 500 eventually, I'd stick with the stock right now or pick up a used LS6 manifold cheap until the time you need the 90 mm one.

I will post elsewhere a new threard some data on various HP figures I've gotten or seen with my own eyes.

 

Lee,

If he has a 2001 and newer, I believe he already has an LS6 intake and block (at least starting with the later-model 01s). I know that my late-year 01 has both from the factory. This was part of the 5 HP and 25 lbs-ft of torque increase over the 2000 C5s.

 

Yeah, come to think of it, you're right. He already had that doesn't he?

 

No, I have a '98

 

Ah, but we couldn't tell from your signature - nice pic, by the way!

 

Until you just said that I didn't even realize that I didn't have it in my sig, I'll go change that....thanx