Big block HP manifolds : head pipes / down pipes diameter question

[Sly_drums]

Hi guys, I need your help on this one. 

My 383 Challenger has Hooker long tubes headers and a dual 2.5 inch exhaust.
I'll get rid of the headers soon since :
-   I want to go back to a more stock looking motor
-   I have clearance problem on the left side with one header rubbing on a tie rod
I just bought a pair of stock HP manifolds that I'm going to install on the car.
Problem is that I need to connect the manifolds to my actual dual exhaust which has been made for headers. Stock head pipes are 2.25 inch wide and I don't want to "reduce" my exhaust at this point.
I got in contact with ACCURATE LTD. They can build "special" 2.5 inch head pipes for me, as it's the actual diameter of the dual exhaust pipe. Anyway I don't know how it will flow with the stock manifolds ? Inside diameter is narrower than headers I think.
What do you adivse me to do ? Order special 2.5 inch headpipes or standard 2.25 headpipes ?

Thanks a lot for your input.

[Moparal]

Standard head pipes.  Make sure the manifolds are for 1970 as 1 side is clocked different than the 68/69     The hp difference you might be worried about is very marginal and on your street car, you will see no difference. Not worth the extra money

[73restomod]

You could port the exhaust manifolds, enlarge the opening to help with anti-reversion, radius/blend the entry in to the main body, and smooth out and enlarge the collector a bit. If you want to go really nuts you could than have it extrude honed. All of which could net an extra 7-12 hp, nowhere near what a set of headers will give, but If one of your main hang-ups is clearance why not go for a set of Tri-Y's?

[anlauto]

Just get new exhaust head pipes

[ToxicWolf]

Just get new exhaust head pipes

   Even the original hemi pipes were 2 1/4.

[Gumby]

TTI sells down pipes that fit the HP manifolds. They are relatively cheap. I can't remember the pipe diameter,
Maybe they can build it to your specs? They need the casting numbers of your manifolds for appication.
There is a section on their website covering this.

[Sly_drums]

Thanks Gumby, problem is that the TTI are aluminized, which is a problem if I need to solder then ? Or is it just aluminized paint over steel pipes ? If yes, then TTI will fit !

[Topcat]

  Even the original hemi pipes were 2 1/4.

Nope. 2.5" until resonator output then 2.25" after was how OEM were.

[Gumby]

Thanks Gumby, problem is that the TTI are aluminized, which is a problem if I need to solder then ? Or is it just aluminized paint over steel pipes ? If yes, then TTI will fit !

You can always just use the band style clamps. Something ike this, they come in all styles and shapes and sizes- even from one pipe size to another, stainless, whatever you want
They don't require welding, and you can easily dis-assemble your exhaust, if need be.
http://www.summitracing.com/search/part-type/exhaust-clamps/clamp-style/band-clamp-lap-joint
They been in use for years ad years and years, and flat out work. NO welding.

I really never understood why people welded stuff together when 1) They didn't have to and 2) dis-assemby is SO much easier and 3) the time it takes for someone to weld - $ per hour - these things are probably cheaper in the long run

[Sly_drums]

Thanks Gumby, looks like the TTI headpipes are what I need, and they sell 2.5 inch diameter.