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On our turbo 5.3, we're running the truck manifolds facing forward. So far, so good.

The question becomes when we upgrade turbo, engine, or both, will the stock manifolds become a restriction? The stock manifolds are handy since they allow good access to the plugs and seem to withstand enough heat to max out our PT88. But, would we gain anything by looking at some custom headers or some shorties? Would there be any benefit into looking at some extrude honing options for the stock manifolds?

Does anyone have any idea what the most power made through factory manifolds is?
 

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asked the same question before and you always seem to get the same answer. "oh they will support 1000+hp" which of course doesnt answer the question but thats what i always got.

it seems that the stock manifolds are good to hold in heat which keeps the exh gasses expanded and helps velocity. but i do feel that atleast a set of shorty headers would help with flow. idk the real answer though but am in for answers.
 

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Ohio boys went 202 with them. I personally feel with 1:1 backpressure, a good set of headers will help a lot, I just have not tested it yet.
 

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I think if you are running a turbo 5.3 you won't find their limits. Mike Brown might have run even more mph than that on an overboost run but I don't exactly remember. And even if Mike or Mark had turbo backpressure, for Mike it would have had more to do with the limits of his 106 and exhaust housing than the truck manifolds.
 

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We have switched from truck manifolds to headers and seen no improvement. This was on a single setup and running 2:1 and higher backpressure. The turbo exhaust housing is the restriction. Not what is connected to the head.

Now if your running a high powered twin setup where your at 1:1 or below backpressure like we are now. Then a set of truck manifolds will be a choke.

If your running a stock block. That will be the restriction long before the truck manifolds.
Unless your running a class where the rules are very tight and the cars are neck and neck. Where you need every last bit of power. I wouldn't even think about running anything but stock cast manifolds. On a motor that makes less than 1500hp.
 

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We have switched from truck manifolds to headers and seen no improvement. This was on a single setup and running 2:1 and higher backpressure. The turbo exhaust housing is the restriction. Not what is connected to the head.

Now if your running a high powered twin setup where your at 1:1 or below backpressure like we are now. Then a set of truck manifolds will be a choke.

If your running a stock block. That will be the restriction long before the truck manifolds.
Unless your running a class where the rules are very tight and the cars are neck and neck. Where you need every last bit of power. I wouldn't even think about running anything but stock cast manifolds. On a motor that makes less than 1500hp.

good post
 

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Discussion Starter #8
We have switched from truck manifolds to headers and seen no improvement. This was on a single setup and running 2:1 and higher backpressure. The turbo exhaust housing is the restriction. Not what is connected to the head.

Now if your running a high powered twin setup where your at 1:1 or below backpressure like we are now. Then a set of truck manifolds will be a choke.

If your running a stock block. That will be the restriction long before the truck manifolds.
Unless your running a class where the rules are very tight and the cars are neck and neck. Where you need every last bit of power. I wouldn't even think about running anything but stock cast manifolds. On a motor that makes less than 1500hp.
Thanks for that!

We're looking to upgrade the turbo first since the engine is still running. We aren't likely to make to the 1500hp threshold before something in the stock bottom end lets loose. Then we'll do the engine.
 
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