What happened to those LT% Siamesed Intake Runners?
 

There were a number of Siamesed Intake Runners back in the 90's that seemed to be a great alternative to porting a stock intake. Does anyone know what happened to these or who made them? I believe DRM had a few on his "Black Widow's".

Thanks! :thumbs:
B-R


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Most of those I've seen were custom jobs. I could be wrong, but I'm not aware of anyone that made up a "batch" of them for sale/distribution - per se". DRM, Haibeck, Lingenfelter, and others including individuals handy with a die-grinder and a TIG welder made some for themselves and maybe a couple others. Not a lot of call for them, except for BIG INCH/STROKER LT5 projects.


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With the latest porting tech of the runners we now have a plain looking external intake actually flowing better than the Siamesed version runners. Actually much better flow has been achieved with stock appearing runners.

Just the facts.

Black Rocket the intake that you have pictured is a new version complete intake.

I'd like to see what some ITB intakes would do on the LT5

I have enough cams and with a bit more head porting and the ITBs who knows the LSV has trapped 129 which is good for a "little motor"

Pete's stock block outshines most anywhere near his displacement and the car turns some great times!!

Pete’s car has run 11.0s at 128+ in the 1/4 and 154+ in the 1/2. Pretty stout for a stock block 5.7L motor.

How would ITB's affect power? Once the throttle is open...it's open...isn't it? Unless the TB is too small for the engine.

Wow, those intakes that Paul Workman posted are a work of art!

So if these were all fabbed up from stock intakes who makes the one I originally posted the picture of?

if you look at the LT5 intake, the air takes a rather abrupt set of changes. air likes straight shot. Look at the c5r through c75 carbon fiber intakes. they have a great design and give the air a straight shot at the port for higher flow

the lt5 intake isn't so bad, but the injector housings (especially on the early cars) have a bigger injector boss as the lt5 originally was slated for a different injector. while you can grind all of this away and pick up a few ponies the lt5 intake is designed more for torq than flow above 6k

so a properly designed ITB gives each port a tapered straight shot, with a bigger throttle plate area. If you look at the lt5 throttle body, we have a nickel size primary, no bueno for anything but sipping through a straw.

With the ITBs it's kinda like big cams (and you need them). You give up lots of low end torq for a fatter top end torq bulge which should make the car faster. It would also provide better access to injectors and I'm looking to go coil on plug with a megasquirt as well. And yes, twin turbos love ITB.

Anyway, it's a pretty expensive experiment and likely to make the car harder to drive unless tuned really well and setup with smaller and longer cross ram style pipes to give the low end. The better flow will give the high end all it needs.

There was a good article on the LS7 (what great cyl heads!!) with ITB. It picked up 30 hp. What was surprising is that it pulled just fine all the way down to 2500 and the low end torq was just fine.

BTW, some of those plenums aren’t siamesed at all. Rather the space between the runners has been filled in and then contoured to look as if it is one runner.

O.K. So what you're REALLY talking about is actually a different intake manifold and configuration. The movement of the throttle plate is an incidental part of the suggestion. Got it. Thanks. I was confused as to how placement of the throttle would affect power...because it wouldn't. :thumbs:

The one in the picture that you posted is a prototype that Lotus had cast for a "next gen" LT5 they were working on. IDK who actually cast that thing.

one pictured sure resembles the 502 GM ramjet

As I recall, Graham Behan said (at a BG gathering) he received that motor in parts from one of his contacts at LOTUS as they were lying around taking up space since the project was cancelled in the mid 90s.

And, according to his presentation at that meeting, IIRC the motor - still a 5.7L LT5 - made ~550 hp at the crank and still maintained its drivability manners!

I'm aware of only 1 other plenum that is filled - and I believe it was in the photos above. My 91 is filled but internally siamesed, and the 95 done by LPE is the real deal - and they dropped the bottom to increase plenum volume. Both make good power, but the 95 makes 620HP / 500TQ from its 385ci.

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620, is that with the nitrous I see plumbed in there?

That is the crankcase ventilation system on an LT5. Fuel rail under the runners.

LT5 TB


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Tom,

Some of us run 63mm TB even w 5.7L motor. However, mating surface on plenum side needs to be port matched to the larger TBs in order to have any benefit.

Yep....I know what a throttle body looks like.

So are you guys (Fastasu and Dom) saying that you're pulling a vacuum at WOT in the plenum then? 'Cause guys are running 58mm TB's on stock L98's too....but it doesn't do anything. With a properly sized TB (big enough), you should have atmosphere in your plenum at WOT...and therefore ITB's won't make a whit of difference (in top end hp).

Changing the runner design...that makes a diff...but that's not necessarily about "ITB's"...that's intake design.