I have read thru all of the posts on this thread and most of the other threads on headers and I see alot of advice about brand names to choose from. What I don't see is anything regarding the different types of headers. Specifically I am talking about Tri Y's vs 4 in 1's. And I haven't seen much discussion in regards to the benefits of long pipes, med pipes, and short pipes with regards to scavenging and rpm ranges for the 5.3 LS1 engine.
From what I hear from my mechanic and from Thorley Headers there are issues with using long pipes if you have to mess with the Cat's at all (legally), in some areas. Also the Thorley rep said if there is a Pre-Cat there would be an issue there. Here is a basic understanding I was given with regards to pipe lengths.
The longer the pipe the earlier you will see benefits in the RPM range. So with a long pipe you will have benefits in the lower rpm range and torque but not as much as you would in the high rpm range with a short pipe.
Whereas if you use a short pipe you will see your benefits mostly in the higher RPM ranges.
I have a friend who is fairly knowledgable about cars although his work is primarily geared towards older vehicles, he has worked with the Lingenfelter teams and NASCAR. So needless to say I trust his word. He tells me that for the most benefit for a large truck that weighs as much as ours we would be better served using longpipes. Although he does add that any aftermarket header would be an improvement over stock.
Now moving on to pipe types. My friend also recommends using a Tri-Y pipe vs a 4 in 1 because you can tune it to the firing and thereby gain more HP and torque.
So to our more knowledgeable individuals here, could I incite you gentleman (and/or ladies if you are out there) to enlighten the masses as to the specific benefits to our vehicles and engines in regards to the two types of headers? I am having some major difficulty finding a Tri-Y header for my vehicle. Any and all help would be appreciated.
As a final note, I do know that Thorley Headers makes a Tri-Y header for the 5.3 L GMC engine (part #310Y-C) BUT he doesn't know whether or not the Av uses pre-cat's because that would preclude the ability to use the Tri-Y they make.
Thanks for your time guys.
