y pipe to single in/single out or true duals?

[redz 1970 K5]

So I just got a sweet deal (on this forum) on some Hedman Headers for the K5.

My exhaust system has had it anyway, so now I am on the drawing board. The truck has a true dual system with stock manifolds and glasspacks now.

I have had late model trucks with dual 2 1/2" in and single 3" out, and I love the sound- low and mellow with a good balance.

I have heard though, if I use the right size pipe on a dual system with the right mufflers, the performance is better.
I was thinking 2 1/4" tubing with 40 Series Delta Flows.

I am slightly leaning towards a dual 2 1/2" in single 3" out with exit on the passenger side behind the wheel.

I know bigger isn't better, and in the past I have sacrificed low end for high end by going too large in pipe. Not any more.

What's your guys' take?

[MMGOODIE]

on my rig I would go with the dual all the way out in a 2.5 just because ever since I knew what exhaust was I was always told dual is better. I could never comprehend the dual 2.5 into a single 3". The air flow does not add up to the same amount which would lead me to belive you will suffer from more back pressure. Just my thoughts.

[bouncytruck]

I'd go 2.5" or 3" dual pipes with an H pipe or a cross over. Definately go with a high quality muffler over the glass packs and consider having the exhaust dump out behind the rear wheels rather than straight out the back - If your K5 isn't sealed up tight, you may get some bad exhaust fumes inside with pipes straight out the back.

[MMGOODIE]

I'd have to agree with BT, if you can seal up the back end dump em over the rearend. It gets so deep and throaty like that.

[redz 1970 K5]

So I am leaning towards a true dual now after what BT said- The main reason I was talking about a dual in/single out is to address harmonics and resonation (which I HATE). However, you're right- I can add an H pipe or crossover and get a better balance between the RH/LH sides and get a more enjoyable note.

Plus, backpressure isn't a bad thing; It's exhaust velocity that is effected. I did a LOT of research on backpressure/exhaust velocity when I did an exhaust for my Vette. So, it's a balance- too much or too little backpressure will negatively effect exhaust velocity. It has to be balanced.

I have been told 2 1/2" true duals is borderline for a stock 350...

The flowmaster site recommends 2 1/4" for a 350 ~ 250HP or so, which is about where I am. Awww, what the hell, 2 1/2". I would hate to redo the exhaust if I built the motor up a little more.

So, true duals with 2 1/2" pipe & H pipe with 40 series delta flows. That is my current position.

[Kleantouch]

Regardless of what or how you run your exhaust- there is nothing like the sound coming form your Flowmasters!!! If you get a chance, while it's still up on the rack, take a picture of your H pipe- my exhaust guy ran 2 1/2 duals, BB Flowmasters for my 454 K5 and said there "wasn't enough room/it will be too close to tthe inlet of the muffler/drops too far down becuase of the transfer case/blah blah blah blah" for an H pipe- so I have duals and no crossover- it still sounds great.
Good luck.

[LUV2XCLR8]

My Buddy Sell Flowmasters And Magnaflows, I Prefer The Magnaflow ,
It Creates Less Of A Interior Hum, Imo, Back To The Question At Hand
If You Go To A Flowmaster Authorized Dealer They Have A Chart In The
Products Book, It List A Cross Reference For What Size Pipe You Should
Use Based On How Much Horsepower You Have, It Actaully Tells You It
Can Be Bad To Go To Big, Not Enough Torque, Or To Small, Less Hp And
Flow, Since I Worked There Pt For 2.5 Years I Thought I Would Share.

Best Place To Run The H-pipe Is Under The Transmision Tail, On A 2wd,
Also H-pipes Balance Out The Sound More Than Anything, For A True
Performance Inhancement You Need To Run A X-pipe, We have Done
Both At The Shop And The X-pipe Seems To Add More Torque. My $.02

[skid]

I'll go against the grain here and say single is the way to go if done properly. Brzezinsky racing www.castheads.com has dyno proven results that a properly sized single will make more hp and torque than duals. Read through their exhaust section and read what mandrel bent pipe and their 2 into 1 collector will do. The reason for this is that each side of the engine helps the other scavenge the exhaust gases. This is the rational for H and X pipes. Why not go single and only buy one properly sized and flowing muffler and pipe?

I have the Brzezinsky 2 into 1 collector with single pipe and can say it made a dramatic difference in the high rpm power. I went with Corvette 2.5" manifolds that were ported (did it myself), into 2.5 mandrel bent pipes, and into the 2 into 1 collector. The output on the collector is 3.5 " but I reduced that into a 3" single pipe and muffler which is all mandrel bent. My engine doesn't make enough power to warrant a 3.5" system which is good to well over 500 hp without restriction. A mandrel bent 3" is good to almost 500 hp...