What is the best alternative intake manifold for a LTx motor?

[B'klyn9C1]

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 reseach 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???

[joelster]

A bigger stall converter.

[Fastbird]

A single plane is a great manifold, but lends it's own issues if you go to use it (tb elbow, adapter, rail adaptation, ect).

Cutting and welding the LTx manifold I believe is talking about taking an LT1 manifold, and adding material to the top side of the runners so it can be opened up to LT4 specs for matching with heads. *edit* I'm mistaken, Mike got it in the next post.

In all honesty, the LT1/4 manifold is a pretty damn good design. It's got decent volume and the short runners help peak the torque early giving it a good SOTP off the line feel.

What I would LOVE to see is a company *cough FAST cough* make an LT1/4 manfiold based off it's big brothers design (LSx), the crossover runner design. It's proven, doesn't cost the top end like the TPI stuff did, and a composite manifold on the LTx would be a nice helper against heat soak (though not a ton). The hindering factor (and why I personally think it'll never be done) though is the LT1/4's SBC 1-2-1 runner configuration. Just not the room to interlace the runners in there due to design by nature.

*passing thought -- What if a company completely redesigned the LT1 heads for an LSx like even spaced runner configuration and brought a crossover manifold to market with it. I just wonder what that would do to the market.

[jakesz28]

Do a search for posts on here from Twisted Z or TwoFast4Lv on LS1tech. He has many pictures of his car floating around and he had the first cut and enlarged plemun LT1 intake that I have seen. His heads also have had the pushrod pinch area welded and ported out farther then most of the guys running stock heads.

What they did was cut the top plemum area off and raised the roof. It gets rid of the hump from the fuel crossover and increase the plemun size.

[joelster]

What I would LOVE to see is a company *cough FAST cough* make an LT1/4 manfiold based off it's big brothers design (LSx), the crossover runner design. It's proven, doesn't cost the top end like the TPI stuff did, and a composite manifold on the LTx would be a nice helper against heat soak (though not a ton). The hindering factor (and why I personally think it'll never be done) though is the LT1/4's SBC 1-2-1 runner configuration. Just not the room to interlace the runners in there due to design by nature.

I was going to comment on why this wouldn't work but you just answered yourself with your next paragraph, lol.

*passing thought -- What if a company completely redesigned the LT1 heads for an LSx like even spaced runner configuration and brought a crossover manifold to market with it. I just wonder what that would do to the market.

The heads would be $$$$$$$$$$$$, figure a new cam, intake, $$$$$$$$$$, new fuel rails, $$$$$$$$$, not sure how the market would respond.

To the OP, the LT1 manifold is not that bad for torque on stock-type motors os bolt-on motors. A simple swap to a higher stall converter can make a stock motored car feel like it gained 75hp.

[mpe331lx]

I think the LT1 produces a nice flat torque curve and good torque numbers inspite of itself and its intake not because of it.

That is a correct statement. The lt1 intake is a mismatch for the stock combo. A stock LT1 has such a flat torque curve due to the fairly small intake ports and small cam. Put a set of 200CC+ heads with a fairly large cam and they tend to be pretty peaky. I was not expecting such a large low end torque loss with the H/C package (although the peak torque numbers rose). A slightly longer runner would help offset some of the torque trade off, but so will a set of optimal gears.