I was at a farm show today (Husker Harves Days), and of course GMC and Chevy both had seperate big display tents. Each tent had the new LBZ and Allison out on a stand for everyone to look at, and of course they had their own representative right there to brag them up every way they could (which I'm not saying is a bad thing). What I cant believe is that GM still uses the same exhaust manifold on drivers side (or both sides for that matter) that they did on the origional LB7's. I've looked and looked and I still cannot figure out why the have to squeeze the manifold where your steering shaft goes by. Clearly there is enough room for the shaft with a normal manifold....
Maybe I'm the only one stuck on this but it sure sticks out when you have only the engine and tranny to look at! The rep had no answer for me as to why they still do this. J. Kennedy has told me that there is probablly minimal loss from this but I would think its got to be harder on your EGT's with the restriction there.
Does anyone here know why GM is still doing this?
Sorry for the long post, just thought I'd see what you guys thought..
Jason

Probably because they already had it set up to make them that way and don't want to bother to change it.

Probably because they already had it set up to make them that way and don't want to bother to change it.

:exactly: .

Ya... probably needed for the 4500 or larger... or maybe even for the Isuzu cab-overs... and they see no reason to change.
I don't think an EGT spike at that point would translate to higher heat at the turbo... in addition to the crossover pipe, it will be "diluted" by the right bank.

Anyone pulled their heads and seen a significant difference in the condition of the exhaust valves or pistons on the left bank?

I may not know alot about these trucks yet but back-pressure and exhaust temps in performance gas engines I do know a little about.

It's hard for me to believe that a dent like that has no effect on EGT and Back-pressure, especially right up near the block.

If that kind of dent was in the exhaust of my SCCA Sirocco I would definitely be seeing changes in performance.

I am not too sure how big a deal this is with the big diesels in these trucks but c'mon! How hard is it to go back to a solid round pipe?

Why make a worthwhile improvement that could possibly help to lower the EGT's on an engine that has pretty hot EGT's:confused: .

I'm with Rich and Kaw, Its a flow restriction. I'm not so worried about it toasting my exhaust, just getting the front of my left head warmer than it needs to be. I'm not saying it would give you MORE boost either, but it sure cant hurt! I'm guessing that only the people with over 500hp would really notice any performance difference, but I think its worth looking in to! May be this winter's project since I didnt get it done last winter.....

I heard some rumors that some companies are developing replacement exhaust manifolds.

:rocking::rocking:
Oh yes... replacements would be nice!

:rocking::rocking:
Oh yes... replacements would be nice!


Where's jesse james when you need him!

):h

From what I was told from friends at GM the clearance is needed for crash protection, not just for clearance when the shaft is in it's normal position. I guess as long as it doesn't hurt anything I can live with it. I have modified a manifold back on a LB7 and measure little to no performance difference and no drop in EGT's when switching between manifolds and running 120 RwHp over stock.

I have modified a manifold back on a LB7 and measure little to no performance difference and no drop in EGT's when switching between manifolds and running 120 RwHp over stock.
Please don't include that tidbit in your literature if you start fabbing headers :D