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I have been looking around to find out how much taller the FAST truck manifold is, compared to the stock and FAST car manifolds. Can someone help me out?
They're around 10 1/2" tall. Too tall for an f-body unless you cut the cowl and remove the wiper motor above it combined with spacers to drop the K member slightly.
I called FAST and they said it is probably 4-4.5" taller than a stock-height manifold. Didn't have any schematics to reference. So I guess that's as close an approximation as I'll get.
I called FAST and they said it is probably 4-4.5" taller than a stock-height manifold. Didn't have any schematics to reference. So I guess that's as close an approximation as I'll get.
That's sad isn't it. They don't even know the dimensions of their own products. But that was my guess in the other thread. Woo.
Yeah, Jake. I was surprised. You'd think that knowing the difference in height between LS6, 102, and 102 truck manifolds would be very relevant information to them and their customers.
Sean, could you please measure for me? Is the 102 any taller than an LS6 manifold? How will you be measuring? Assuming that the manifold rests on the lowest part of the flanges, then just setting each manifold on a table (like in the picture) and measuring the height from table surface to top of manifold should do the job. Maybe I can talk some guy at FAST into doing the same with the truck manifold.
Thanks for that info Sean. Did alot of info searching but couldnt find a clear answer. Pretty sad FAST doesnt have their products dimensions measured out.
Thanks, Sean! I assume that the undersides of the intakes (the places where the intakes made contact with the table) would not account for any of the difference in height?
Now I just need someone to measure an LSXrt manifold! Anyone?
Here's something to think about...according to the Hot Rod 20 intake shootout, the 102 and the truck intake were within 1 or 2 hp of each other. In other words, there isn't really any advantage to the taller truck intake.
Regarding the LSXRT manifold, the upward angle of its snout pitches the throttle body up at an angle. This can also cause clearance issues with the hood. The air intake tube that attaches to the TB can be tricky to get situated because of the upward angle of the TB.
For my 91 RS Camaro the LSXRT fit under the hood and the TB cleared but the air intake tune didn't. This required a custom metal air tube with the very top shaved flat and a plate welded to it.
LSXRT on my 3rd gen Camaro
The shaved air tube is visible in the above picture. The one below may offer a better view.
The driveability Of the LSXRT was terrible on my small cam 383 LS1 stroker. In actual dyno testing the LSXRT proved to be consistently 2hp worse than a modified 90mm snout ported LS6 intake on my small cam 383 LS1. Big cam the LSXRT would have done better the Fast LSX was within 1 hp of the LSXRT on my engine.
The air flow experts I've talked too say that sort of outcome sometimes occurs - and none of the were surprised.
Had I known then what I know now the LSXR would have been a wiser intake manifold choice for my car. It would have fit without the custom air tube. The tuning would have been more straight forward.
On the other had I did end up with a nearly new LSXRT intake manifold sitting on the shelf collecting dust. I've used it in my intake manifold flow testing. The LSXRT does flow very well but for real sucess with this manifold I think 400+ cubes engines and a big solid roller cam plus too notch cylinder heads designed for that sort of application are a good idea.
Best wishes for your project and sucess.
Last edited by 99 Black Bird T/A; Apr 24, 2018 at 09:08 AM.
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FAST 102 LSXrt manifold height? 
