what is the exit diameter of the bbk exhaust headers for the 97 4.6l i was looking on some sites and couldn't find it, in my experience with exhaust, take ur header exit diameter and go with that for the best flow.

 

Like these? http://www.bbkperformance.com/produc...t-headers.html

2.5" to match the rest of the existing OEM system.

MGD

 

2.5 and larger and you will start loosing low end torque.

 

all i want is 2.5 then then the air volume leaving the engine should be maintained and no torque lost

 

If yer going into a single ( 'Y' ) pipe.

If yer going to run duals, use 2.25" - especially on a 4.6.

MGD

 

i wanted an x pipe to lower and help balance out the frequency's for a smoother note

 

That's not it's primary purpose (which is to promote scavenging).

If so - use 2.25" or you will notice a loss of bottom end. Remember - a non-PI 4.6 has a dearth of low-end torque to begin with. ANY loss is not gonna make any faces.

MGD

 

where should the piping size change? before the cats, in the cat, before x, ya'll goofed with these trucks for a while so ill listen to experience

 

actually im curious now as to what the advantage of the bbk headers would be, should i save that chunk of change for the top end of the engine?

 

Well, yer shorties are 2.5". If you keep ye stock cats, they are also 2.5".

So - you can reduce at that point to a 2.25" x-pipe: http://www.troyerperformance.com/cgi...atalogno=10790

Or run a 2.5" x-pipe: http://www.troyerperformance.com/cgi...atalogno=10791

And reduce to 2.25" mid pipes to 2.25" SI/SO mufflers and so forth.

I doubt it will matter all that much so yer choice. I know mandrel SS is costly and perhaps hard to find, but it's the best. Anything else is not fatal but still a compromise.

How picky are ya?

The bench racers on here will have a field day with this one!

 

Good catch, bud. PI heads will indeed be a better investment. A well-known tangible improvement.

Shorties are overrated - marketing BS.


Hey! I'm just a Geek - where are all the REAL experts?

Seriously - ask/PM a Mod to get this moved to the Exhaust section - the gurus hang out there, lol.

 

with the PI heads do i need the new intake, they run about 4somthing each from what i was finding, about a grand total with the larger intake
thats more then i want to budget for right away after all i bought this truck to be a tool untill i graduate, then ill get my a new truck hopefully as i begin an engineering career and keep this truck for a toy

the heaviest things ill be pulling is a tractor on a flat bed and maybe my 1970 skylark (on the flatbed if i cant borrow a dolly) as i get more done with that project (been goofing off on that since i was 13)