completley new exhaust

[Kuskoal]

last thoughthey guys, im posting here because i cant get a straight answer: i know ive posted here about tri-y's, xpipes and whatnot, but now im starting to do my homework on a new exhaust for me truck. i think ghunt explained to me how tri-y's are superior so im sticking with those. my other questions are: Would a single or dual exhaust help with low-midrange torque? What size pipe(s) are sufficient for a 302? I want the exhause pipe to exit in front of the rear tires for a different look, good idea or bad? glasspacks or standard muffler? if it was dual exhaust and they are close-running would and X/H pipe help scavenging?

thanks alot for the help/advice in advance

[dkf]

True dual 2" or 2 1/4" with an X or H pipe will work good, however for best low end a single 2.5" would probably be best. The x/y pipe will help balance out the system. I don't have one on my 74' 302 but the next exhaust will, I want to see how much difference it makes. What muffler to use depends on how loud you want it and how much you want to spend. You have the right idea going with tri-y headers.

[Bear River]

I second that a single exahust will tend to be more consistent on the low-mid range on torque. Exiting in front of the tires is fine. I don't think anyone has done an honest comparison in performance of doing it that way, but I don't see why there would be any problems so long as the pipe runs are smooth as possible.

For the muffler, I would steer clear of glasspacks if you want to do the job right. Glasspacks are popular because they are cheap and they are loud. But from a performance standpoint, and Magnaflow or some other straight through design would be better. Or use a Flowmaster design if you want it to be loud.

If you di go with a dual exhaust, an h-pipe or x-pipe is almost a must if you want a smooth tone and low end torque. Or you can use a dual in/dual out muffler, that, while not quite as good in terms of performance, is great in terms of sound. Its louder than having two seperate mufflers.

[Kuskoal]

hey thanks for the feedback guys. Bear River, i read your article on exhaust systems but it left aout some questions i still got.
1:wouldnt an x pipe work the same like a y-pipe for single exhaust?
2:why arent glasspacks a good idea? (details if you can)
3:how is a single exhaust actually more torquey? if i did go single exhaust how big would the pipes be? (exiting engine pipe diameter and merging into one pipe diameter) my dad told me that 2.25" (stock i think) is best left that size. if you could clear this up that wraps up my questions on exhaust.

[TallPaul]

Why are glasspacks not a good idea? Well the most popular glasspack, Cherry Bomb, is restrictive according to this guy who cut one apart:

http://www.greenfries.info/Resonator.htm

And you can see the smaller diameter inside by looking down one in the store. Some Cherry Bomb type mufflers may be fine though, maybe the Flowtech Red Hots.

[Kuskoal]

eh i use the cheapy summit racing one; it dosent restrict flow and gives great sound.

[Bear River]

Originally Posted by Kuskoal

hey thanks for the feedback guys. Bear River, i read your article on exhaust systems but it left aout some questions i still got.
1:wouldnt an x pipe work the same like a y-pipe for single exhaust?

Yes, though the effect is not as strong. I will attempt to explain more as an explanation to #3.

2:why arent glasspacks a good idea? (details if you can)

As explained by TallPaul in his link, and by defining a glasspack as the common unit the term refers to which has the louvers protruding into the exhaust stream, you can see it creates a lot of turbulence. As I stated in one of my other posts, glasspacks are popular because they are loud and because they are cheap. A resonator is better than a glasspack in terms of performance, because they do not neck down or protrude, and they have a smoother interior surface. However, they don't sound quite the same, and they suffer some of the same drawbacks.

3:how is a single exhaust actually more torquey? if i did go single exhaust how big would the pipes be? (exiting engine pipe diameter and merging into one pipe diameter) my dad told me that 2.25" (stock i think) is best left that size. if you could clear this up that wraps up my questions on exhaust.

The single exahust with a y-pipe is more torquey for the same reason that a triple y header is more torquey than the common collector design. That is, that the hot expanding gases will create a relative vacuum in the opposite bank, helping to pull the spent exhaust gases out of the cylinders and increasing the volumetric efficiency. More volumetric efficiency = more torque. A dual exhaust lacks this extra y, and MIGHT loose the benefits of this effect.

A dual exhaust is also easier to mess up with and requires more time and materials. The y-pipe helps smooth out minor variations in flow and helps built exhaust velocity and helps keep the exhaust hotter, which is beneficial to power (which is why some people wrap the exhaust in an insulating material and part of the reason OEM has heat shields.) A dual exhaust more surface area where heat can be lost, and the surface of the pipe also work to slow down the exhaust in the form of friction.

H-pipes and X-pipes helps overcome some of the dual exhausts weaknesses. Dual exhausts do have their strong points, for example, their power producing potential can be greater, especially if mods that result in greatly increased airflow are used. Most mistakes in the design tend to air on the large side, since many people forget that since pipe is round, a larger diameter is actually much larger. Doubling the diameter does not double the volume, it actually more than triples the volume. Where a single 2.5" exhaust may be appropraite, dual 2" pipes are actually significantly larger than the single 2.5"

One of duals exhausts features is the sound. Dual exhausts tend to have a raw sound that many people like. The single exhaust will typically be more indistinct. The duals also tend to be louder and deeper. However, don't put single exhausts down for the count . While I have not personally verified this, I have heard from several sources that a single exhaust with a dual outlet muffler is actually louder than a dual exhaust with dual mufflers. This does make sense when you consider that a dual exhaust has two mufflers, while the single exhaust has just one. Two mufflers will absorb more sound that a single muffler, and the dual outlets help project the sound.