Kit versus custom exhaust?

[shadango]

I am trying to decide whether I want to go with a kit exhaust and spring for headers or have a local shop do the exhaust for me using my stock manifolds...

I have a 318 with J heads......I was told that I may be better to stick with the stock manifolds....I was told the motor is stock internally.

I want duals and I think Dynomax SS mufflers......I have that muffler on my 318 dakota and it sounds great...

I know I can get a mandrel bent kit with muffs --- but then I cant get the muffs I want...plus, I would pretty much HAVE to get headers since I have no header pipes right now.

Help me make some sense of this conundrum!

Or I can have a local shop do custom bent 2.5" aluminized steel for me, but not mandrel bent, with an x pipe and whatever muffs I want for under $500....using the stock manfolds.

[Chryco Psycho]

m,ost 318 manifolds are restrictive unless they are the upswept 340 style
 if you decide to use headers you really only have 3 choices , TTi , Dougs or the Hooker 5115 , every other header drops below the steering .
 Headers usualy flow better & increase power as will mandrel bend exhaust , not crush bend as would be done locally & usually the cost is about the same buy prebent mandrel as having a local shop do it at least it is here

[shadango]

I understand that the 318 stock manifolds wont flow well....

But, with my J heads, it has been suggested to me that I DONT want headers since the j heads already drop my compression a bit...I was told that headers may hurt me....is this way off then?

[moper]

Headers wont hurt anything but speed bumps unless you spend some real money. I would keep it simple. Bring it to a shop and have them custom bend a set for you. And, you may not want anything bigger than 2 1/4" for the head pipes. The manifolds won't accept anything bigger. So one way or another, the pipe at the manifold opening will be 2 1/4" ID. A nice sound is 2 1/4 headpipes with your choice of mufflers, no resonators, and 2 1/2" tailpipes with the tips modified to fit 2 1/2" pipe. (cut off the 1 7/8 bend and replace with 2 1/2").

[MEK-Dangerfield]

If performance isn't an issue, then I would agree with moper and just have a custom exhaust done up. When you look into the price of Doug's or TTI headers, you'll see they get costly, then you still need pipes from the collectors back.


  Mike

[moparniac]

TTI 2" headers with Big 3 1/2" mandrel bent gun barrels..... stock setup 

[shadango]

stroker thats awesome!

Performance isn't the main concern but I sure would like to get whatever I can in this process.

SO, the J heads DONT hurt me as far as headers?

The local shop said he could hook up to headers too.....he was planning 2.5" tailpipes and the smaller headpipes if I kept the stock....

[73Chally]

If performance is a factor, then you do not want to go bigger on the tailpipes vs. the headpipes.  At worst you want to stay the same size, or ideally go one size smaller.  As an example, you would use a 2-1/2" from headers/manifolds back to the exhaust, and 2-1/4" out the exhaust to the tailpipe.  It's been discussed before, but it has to do with back pressure and exhaust flow velocity.

[shadango]

What if you go headers though?

[Chryco Psycho]

header affect things good & bad , you can use a longer duration cam & take adavantage of the scavenging using headers , , the better flow will not hurt either but the real gain on a smaller engien with a stock cam will be less . If you are using the car mostly at low RPM as a cruiser the gain will be minimal , itt really depends what look you want & what you want to use the car for .

[shadango]

I ordered Dougs headers....so now have to figure out the rest.....

Still not sure I want to do a kit...I think having some tube bent locally will be fine for what I am doing.....

I do want to do either an X or an H pipe.   WHat do you prefer? Do X pipes make as much low end torque as the H pipes do?   I read somewhere that the sound is different between the two....  A Jegs universal X pipe kit is $85 and the univ H pipe kit is $43....

The car will be mostly a cruiser but will want performance as well.....hence the headers and X or H pipe....

Will the sound be different if I go 2.5" pipe from headers to muffler and 2.25 tailpipes?

I am also thinking about having the shop put in flanges so I can pull the x pipe section and mufflers "just in case...thoughts on that?

I also want ss tips for the bling factor...LOL

[Chryco Psycho]

unless the X it correctly made it will interefere with the floor pans & force the exhaust to hang too low
 I would use 2.5 all the way back , actually with a 318 I would use 2.25" pipe all the way
 everything changes the sound from X or H pipe to all the different muffler types

[shadango]

The shop says that they can fab an X pipe up.....so it wouldnt be universal if I went that route......

Seems like all the kits I have seen are 2.5, plus mandrel bent......

Magnaflows are 2.5" all the way.....Dynomax's is too, I think.....

Someone had suggested that going 2.5 to the muffs and 2.25 tailpipes help scavenge gases better.....but that 2.5 all the way would work too,,,

 

Seems like there are lots of favorite setups and combinations out there....LOL

[73Chally]

For a 318 that's going to be a street car, I think your best bet will be to just get a set of 2-1/4 pipes all the way back, bent at the muffler shop, with no X or H connection.  Get a good pair of mufflers, and the stainless tips.  To get the best performance out of the X connection, it needs to be specially set for your car.  The universal kits are based on a "best case scenario" that is pulled from data from multiple cars/engines/setups.  Unless it's a custom install for your car with specific tuning, it will do you no good performance wise.  It will give it a different sound, but so will different mufflers.  It kind of sounds like you're overthinking the whole thing.  If you were building a big horse small block that would see a good bit of strip time, then all these considrations would be more valid, but for a basically stock 318, just go with a basic setup.

[shadango]

Oh, I know I am overthinking it...LOL

But in the back of my mind, I always try and optimize what I have going.......I do plan on maybe playing with the engine going forward...maybe a cam, who knows.....so I dont want to "under exhaust" it when I am starting with a fresh slate.

I figured the 5115s could be a tad large for what I am doing, so went with the Dougs.

The X pipe info makes sense....the kits have them but are tuned specifically.....I have been shying away from the kits thinking that the final result would be better if I have a local shop do it.