Question: LB7/LLY intake runners vs. LBZ/LMM

Drholliday

Drholliday

Member
May 28, 2008
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Gresham, OR
Just curious what the hype is about the LB7 vs LBZ intake runners is. I've set some side by side and the runners are identical except for the mouth that the y-bridge bolts to. The LBZ has a bigger mouth, but runs into the exact same size runner (and the top of the mouth runs into a metal wall). Just curious if anyone has done a before and after to see what the actual flow difference or power gain is.

Not the greatest picture, but it shows the difference in the mouth.
 

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paint94979

paint94979

Beer Nazi
Sep 18, 2006
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We see hp gains and EGT reductions by going from Stock Uppipes to slighly larger ones... You are increasing airflow by removing one bottleneck in the induction system. Most will agree that swapping to LBZ runners and y-bridge is one of those things that if you're rebuilding do, if you are swapping turbos do... i have weighed the time to benefit ratio and unless i am doing something big with my truck i won't be touching the runners
 
TheBac

TheBac

Why do I keep doing this?
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Apr 19, 2008
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I honestly dont see the point in switching to LBZs, but thats me. Same basic designs. Russ's ideas could be an answer, though.
 
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maine04max

maine04max

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Dec 11, 2008
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i can see changing over to a fed y bridge if you have a cali lb7 .......the cali y bridge is a huge restriction ...... my plan is to cut off the inlet and weld in a 3 in 45*pipe , kinda like ppe does
 
D

Darius6t9

I'm the Floater. Lurking.
Aug 23, 2008
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Rusk, Tx. Again
I am probably wrong, but here is what it looks like to me. Just from looking at the one picture, I am guessing that where it looks like it kind of necks down some, it is causing a venturi effect, causing the airflow to speed up some. But that is my uneducated guess.
 
McRat

McRat

Diesel Hotrodder
Aug 2, 2006
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www.mcratracing.com
IIRC, the minimum ID on the LLY is about 1.9" and LBZ is 2.3"? Point of greatest restriction in a Dmax is that bridge.

Been awhile I should go look again. We've been running LBZ intakes on Casper for 3 years or more.
 
SHOTZY

SHOTZY

<"Whats next??"
Aug 27, 2008
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melbourne, fl
Well seeing this thresd is getting some attention I'll ask this ? again. I made this switch and cant post any results because I'm lacking one piece. I need the elbow that slips into the y-bridge.(LBZ) Does anyone have one of these? I will buy it today! Been waiting forever for this piece. GM or Isuzu I should say is killing me with the back order crap. :( Thanks for any help.
 
SgtKilroy

SgtKilroy

'Merica!
Sep 30, 2009
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SoCal
I know I'm bringing back an old thread, but I have some questions about swapping from LLY to LBZ runners/Y bridge and didn't wanna start a completely new thread. The main question is can the swap be done without removing the turbo? Are the seals between the runners and bridge ok to reuse, or should they be replaced just on principle? The seal between the runner and the head is just permatex gasket maker correct? Will any sensors have to be replaced with the LBZ version or will they swap over?
Thanks for the help!
 
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