Header vs. stock manifold & dual out w/ Y-pipe

[Anonymous]

would I get relativly the same HP/TQ increase with the stock manifold, Y-piped into duals with maybe 3" piping and flowmaster 40 series, that I would with a dual out header and flows? would the dual out make that big of a difference? This is by the way for a mild street cruiser that basically just needs to look good and sound good. Thanks for the help,

Chris

 

[Asa]

nope, the headers flow better, the stock ones are just too restrictive

and if you put 3" pipe on a 200, expect to lose power

 

[Anonymous]

I feared as much, well I guess I'll bite the bullet and buy the header.

Chris

 

[ludwig]

You won't be disappointed. Make sure you get some kind of bold retainers for the header and high temp gasket sealer. If you still have the heat riser choke pulloff, there is an aftermarket gizmo, a little domed shroud with a riser pipe to feed the choke pulloff. It is about 1"x1.5" and uses a radiator clamp to secure it to a pipe.

 

[Anonymous]

Ok thanks, would anyone know where I can get a good cheap single or dual outlet header, maybe someone has one lying around, or knows a good website, Thanks for the help,

Chris

 

[falcon fanatic]

Yeah, check the link on the fordsix.com website, or go straight to http://www.fordsixparts.com/
You could also go with clifford's. that's what have and it is nice, but they are weenies most of the time when you talk to them, and their prices are a bit steeeep.

 

[CZLN6]

Howdy Chris and All:

The difference between a log exhaust manifold and a header system is the individual pipe leading away from each exhaust port. If you ever have an opportunity to play with a head on a flow bench, hold a pipe up to the exhaust port you are flowing and watch the cfm go up. YOu just can't get the same results with a cast log exhaust manifold.

The center port divider does that for a short distance for the siamiezed center ports, making them comparible to the rest of the exhaust ports.

But, in reality, the biggest power increase of headers over a cast log manifold is at higher rpms and at higher volumetric efficiency levels. If you are really satisfied with "a mild street cruiser, that looks good and sounds good", consider this- To get the maximum benefit of headers you will need to upgrade your entire exhaust system. How about building a performance 2" exhaust system, using the performance muffler of your choice. Later on, if you find that you're still not satisfied with your engines performance level, your only expense will be adding a header to your already in place performance exhaust system.

PS- A used header may not be worth the trouble. There is usually a reason it is not in use. Look closely. My advice is to buy it now, have it coated- inside and out, install it right and enjoy.

Adios, David

 

[Anonymous]

I'm going to add sidepipes to my car but stick with the stock exhaustand a y-pipe till i canafford a header...but it should still be better than stock...

 

[michael_cini]

hey david,

what you wrote is great advice...but i'm not surprised since your book is a great read too! i think this is what i will do on my 63 falcon for now. what exactly defines a 'performance' exhaust? and what do you prefer for a performance muffler? thanks.

best,

michael

How about building a performance 2" exhaust system, using the performance muffler of your choice. Later on, if you find that you're still not satisfied with your engines performance level, your only expense will be adding a header to your already in place performance exhaust system.

 

[Kstang]

I saw a clifford header used for 150 on stang net.

just thought some of u might want to look it up.

http://forums.stangnet.com/showthread.php?t=450489

 

[ludwig]

In "Tuning for Power", David Vizard has a useful explanation of why tuned headers work. With each detonation a puff is formed in the pipe. In a stock header these puffs are irregularly spaced puffs of varying pressure followed by a pressure void. In a tuned header, the puffs are emitted with similar pressure at regular intervals. The headers turn a series of irregular puffs into somethng approaching a constant, moving column without voids. The moving column helps to draw spent gas out of the combustion chamber. When the pipe gets too big, the suction/column effect is reduced and the chamber must be emptied with pressure from the exhaust stroke alone.
Backpressure is essential to performance as well and too little will cause a drop in HP. It keeps the escaping gasses from turning a sharp corner and going up a neighbor pipe as happens in a regular log manifold.
This is a floridly shortened version of Vizard's explanation. Addo, Jack and Slade can or will provide commentary about backpressure and other exhaust issues. I bow to their expertise.
Don't expect a big bump in performance until you get real tuned exhaust headers to go with the less restrictive muffler and pipe system.

 

[CZLN6]

Howdy Back All:

Michael- My definitions of a performance exhaust system varies, depending on the combination. With a cast manifold anything more than a 2" system is a waste, in my opinion. I prefer a Walker DynaMax turbo muffler. It is throaty, but not too load, and very effieicent. Opinions vary considerably on what sound is desired. Compression ratio and muffler placement both have an effect on exhaust sound. In general, the farther forward the muffler is the better the rap effect, and vice versa. What's your pleasure?

With dual outlet header, a 2" system and turbo mufflers.

With a single outlet header, and 2 1/4" exhaust system with turbo mufflers is very effective. The area of the tube is the difference- and heat build up and velocity.

Ludwig makes a great point about the pulses or slugs of exhaust. These pulses create a freight train effect and tug along the next. In the 60's great efforts were made to design perfect 180 degree exhaust systems. That design is not available for our engines, but the relatively long tube headers available are a big improvement over cast manifolds. Think of the exhaust as beginning with the combustion burn, the exhaust valve opens and hot, expanded air is looking for somewhere to go. It rushes out the opening exhaust valve, almost immediately it begins to lose heat and, consequently volume. What's to keep it moving? Another pulse hits it from behind and pushes it along. And the pulse evacuates the combustion chamber and creates a vacuum behind it, timed to coinside with the intake valve opening and a fresh charge of mixed Air/fuel is drawn into the chamber.

Adios, David

 

[ludwig]

Ahem, I meant David.

 

[Anonymous]

Ahem, I meant David.

???

 

[ludwig]

Shjeldal.

 

[michael_cini]

Michael- My definitions of a performance exhaust system varies, depending on the combination. With a cast manifold anything more than a 2" system is a waste, in my opinion. I prefer a Walker DynaMax turbo muffler. It is throaty, but not too load, and very effieicent. Opinions vary considerably on what sound is desired. Compression ratio and muffler placement both have an effect on exhaust sound. In general, the farther forward the muffler is the better the rap effect, and vice versa. What's your pleasure?

thanks for the advice david. my pleasure would be to have a nice throaty sound without being much louder than the present stock muffler.

so if i am to do as you suggested, use the stock exhaust manifold and update my exhaust system for the present and possibly add a single outlet header later which size pipe would you suggest? 2 or 2 1/4.

thanks.

michael

 

[CobraSix]

What other mods to the engine are you planning? If you are keeping with a fairly stock engine (basically, leaving the intake log intake, or with a 2v adaptor), I think 2" will be great for single out headers. If you were going Aussie, or Offy, I said 2.25" exhaust for a single system.

Another thing that changes exhaust sound: Cam. I upgraded my cam, and the sound of the exhaust became louder and throatier.

Slade

 

[Anonymous]

"Backpressure is essential to performance as well"
Vizard is quite adament in the opposite direction: absolutely no backpressure is good, ever. If the car is faster with any backpressure, it means the jetting etc. is wrong.
"Tuned" length exhaust has almost no effect with low overlap cams, since the period during which both valves are open is very short and the common curtain area is too small. The inertia-based extraction effect still works, though. For mild cams, the most important design points are diameter and departure angle (primary leaving the port without a sharp bend).

 

[Anonymous]

I read recently that the minimum size of the collector is a function of primary diameter and # of cylinders connected to it (already known). What was different was the amazing amount of math to demonstrate that the change in area from primary to collector should be 1-6 (i.e., collector area = 6 X primary area). How can that be? The collector for a 6-1 with 1.50" primary (1.402" with 18 gauge tube) would be 3.53" - way bigger than normal?
Because the total expansion area consists of the collector ID, plus the area of the 5 other primary tubes. If this is taken into account, the OD is the same as the primary (1.50"), which may be why 6-1 collectors are less efficient than 3-1 collectors, where the minimum OD by formula is 2.08".
Where the collector ID is too small the expansion area is not sufficient; the "echo" return pulse amplitude is too weak for maximum extraction effect at the exhaust valve.
Where the collector ID is too large, the "echo" return pulse amplitude is strong enough, but the velocity and density of gas in the collector is too slow and thin to make another strong & useful pulse when the collector ends. This throws away the potential use of the remaining gas energy.
It appears from this that adequate collector area for flow takes precedence over secondary pulse return, since all collectors are designed larger than needed for best primary pulse strength.
In a muffler/tailpipe system this doesn't matter, however.
It looks as though 2 X 3-1 systems have a nice compromise, where by comparison a V8 (where the collector would be smaller for the same primary) has theory and practice more widely separated - the collector is always too big for good secondary pulse
A 2 cylinder is completely out of luck, since the collector would be much too big: a 1.75" primary (common Harley size) would need a 2.96" collector for the best primary pulse, and that means the collector would have almost no effect since the secondary pulse would be too weak.
My heads hurts.

 

[ludwig]

Whoa. You read past where I stopped. My eyeballs were throbbing by then. Props to you man.