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Discussion Starter · #1 ·
Is there a set that fits, or are the Hedman 68600 headers the best that we can do? I really want to buy something off the shelf that works. I don't like building headers. I've done it a few times, but I want to avoid lengthy sub-projects on the V8 swap such as a month-long excursion into building the perfect set of stainless steel headers.

There is also this nifty cast manifold from Hooker:

Hooker 8527HKR S/B Chevy Exhaust Manifolds, D-Port, Natural{match_type}&msclkid=57f7aa1e171913b8e274cb93402c8dd9&utm_source=bing&utm_medium=cpc&utm_campaign=SMI%20-%20Shopping%20(CSE)%20(Bing)&utm_term=4577404346894280&utm_content=All%20Products%20(Feb28_2020)

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Then there is this "ram horn" style with an actual collector inside:


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Discussion Starter · #4 ·
Tubes are what make headers work.
Something to do with flow and scavenging.
It's not so much the fact that it is tubing as it is the consistency of the inside profile and the gentleness of the bends compared to a cast iron manifold. It's not that a cast iron manifold couldn't be made with performance equal to a tubular header, but the reason cast iron is used for manifolds (other than cost) is that casting allows for the super tight turns, convoluted shapes, and squished areas that make packaging an engine into an engine bay easier.

...would be a compromise in exchange for reduced performance.
This we know. Most any cast iron exhaust manifold will be a compromise for the simple reason that compromise is the reason the manifold was cast in the first place. I always have to keep in mind that this is a family hauler that I want some great power out of. "Family hauler" and "great power" will be at odds with each other as I make decisions for the van.

"Great power" means that I'm doing the swap in the first place. It means it will have ported heads. It means it will have a little cam to it. It means that I am stepping away from the TBI that otherwise does a great job spinning the torque converter enough to move the van.

"Family hauler" means that it has to be utterly reliable in all circumstances at all times. It means that I can't have solid lifters because I can't afford the time for upkeep, knowing that I am leaving power on the table by going hydraulic. It means that the exhaust system has to be reasonably quiet so as to allow conversation while driving and not to annoy my non-hot-rodding wife AND has to be consistently leak-free--something that headers with 1/4" head flanges are not famous for. It means that I have to keep lift, duration, and LSA in check so that fuel economy and drivability are minimally affected, so that it has a good enough idle that it can seamlessly support AC operation at a traffic light, so that it does not require a high-RPM stall speed in the torque converter, and so as to keep fuel economy decent enough for long road trips.

So, I am already deep into compromise. The question isn't whether or not a better-than-stock cast manifold is a compromise, but rather if it is a compromise worth making to have a manifold that stays flat and quiet.

Shorty headers themselves are a compromise; they are nowhere near optimal in tubing diameter, primary length, or collector merge angle. They are a compromise for packaging concerns, offering some of the benefits of headers (smooth turns, consistent ID, decent scavenging) and one benefit of cast manifolds (decent fit.) In turn, they bring the disadvantages of having less than optimal design and requiring some additional attention to keep them quiet (i.e. gaskets probably won't last as long and the possibility of cracking is higher than with a typical cast manifold.) So with shorties just as with cast manifolds, the question is whether they are a compromise worth making.

Shorty headers and aftermarket cast manifolds are basically the same compromise with one leaning toward durability (and away from performance) and the other leaning toward performance (and away from durability.) How far each leans in its respective direction, i.e. how much power and torque a cast manifold loses and how much durability a shorty header loses, I don't know. And the direction I lean in that compromise is something I have to figure out for myself. My experience (in my previous import life) with street type headers has been generally positive. Head flanges were typically 3/8" or thicker and dimensionally stable enough to keep a good seal. Performance was not perceptibly better than with a good cast manifold setup, but that was on a 2.0L engine that makes 150HP at best with everything being perfect. On a SBC, the difference between a stock head-back exhaust system and an optimal head-back exhaust system is worth nearly the total amount of power available from those little VW engines I played with before.

I'll try to put some numbers to it: I suppose if I could buy a pair of performance cast manifolds that never ever warped, cracked or blew a gasket in an untimely manner (i.e. faster than stock,) I would be willing to give up 30-40HP to get that peace of mind. Conversely, if I knew that I could gain 50HP over those performance cast manifolds at the expense of a once-yearly gasket change, I would do it. If I knew I could gain 100HP, I would be willing to invest the time in duplicating their design out of better materials so that they never fail.

And no matter what, I won't have anything near a stock exhaust. I am planning to employ David Vizard's "zero loss" exhaust system to the best of my ability given packaging compromises that are necessary.

I would be interested, as I think of exhaust, to see your routing for your driver side exhaust on the V8 van. The fuel tank is a bit of an impedance on the driver side of a dual system, and I am thinking about how best to get around it.
 

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Discussion Starter · #8 ·
This is incorrect.. you apparently do not understand how "tubes" work with regard to flow and savenging.
Actually, it is correct, and I do know. Tubing is nothing more or less than a cylinder shape with no caps on the ends. There is nothing inherently superior to the fact that it is a tube, which is a rolled and resistance welded piece of sheet metal. Flow characteristics, or scavenging characteristics for that matter, of a piece of tubing are purely a function of ID, length, and pressure differential, and nothing else. You could make a cast iron cylinder that would flow precisely the same as a piece of steel or copper or plastic or paper tubing or steel pipe, or a wood log with a hole drilled down the center of the same diameter, given that the cast tube is free of excessive roughness that adds up to disturbance of the flow. (A little roughness is fine and does not affect flow unless the air is being shoved into the roughness such as on the outside radius of a turn.) If you built a steel tubular header and used it as a plug to make a duplicate cast manifold, the flow characteristics would be the same provided that the inside of the manifold was free of defects or otherwise cleaned up to be made free of defects.

The difference is design, not whether the manifold is cast or made from tubing. A cast manifold of the correct design would do just as well. With that said, an optimized cast iron manifold would be too heavy and probably more expensive than a tubular header--and it might be more prone to cracking given cast iron's poor ductility brought on by its high carbon content compared to steel.

Scavenging is the effect caused by an area of low pressure following a pressure wave down the tube. Engine exhaust is a series of pressure pulses, each pulse followed by an area of low pressure. The area of low pressure offers a tempting target for the next pressure wave to follow. The "scavenging" itself happens in the combustion chamber during the overlap period when the low pressure are behind the outgoing exhaust pulse helps to draw remaining exhaust out of the chamber and pull the incoming intake charge across from the intake port. What happens right then is why primary tube length and diameter and collector length matter. It's why we don't want to undersize (restriction) or oversize (lost velocity) our primary tubes. If not for the need for velocity and the scavenging that comes with it, then the solution to every performance exhaust question would be "the biggest tube possible and the shortest distance possible."

Certainly there is no cast manifold on the market for a SBC that is optimized for performance. It could exist, but it doesn't and won't exist.

What you have is about what I expected for exhaust routing, and it gives me an idea of the space I have to work with. My van sits in a low ceiling garage AND has running boards, so my ability to see underneath without pulling it outside is limited.

Downstream of the headers or manifolds, my plan is to build David Vizard's zero loss system. Here's a link:
Vizard has literally written the book on so many engines. I believe that he has authored or co-authored 35 books on the subject of engine building. He doesn't spout opinion or say or do anything that is not directly backed up by the flowbench and the dynamometer, so I am inclined to believe that his zero loss system will do exactly what the name suggests given that it is built correctly. If you watch the video, you will see that the system employs a "termination box," which I believe "tricks" the engine into seeing open air, simulating the end of the header collector pipe. His video suggests that each bank in a dual system gets a termination box and a muffler, but he does show one version with a common box then dual mufflers.

I am not sure that I would have space for a dual side exit system like yours AND a termination box for each side. Maybe if I went with a termination box and side pipes, provided that the termination box could hush the exhaust enough for side pipes to be civil enough for a family hauler. That's a big if, because I have never seen a side pipe exhaust that I would call quiet.

If for some reason I am forced to bring both banks down the passenger side, I will probably leave them there and either collect them together or dump them out separately but on the same side.
 

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Discussion Starter · #10 · (Edited)
You seem to know things, yet with all this information, and you still missed the point.
Your point, as I interpret it, is that tubes inherently flow and scavenge better somehow: "tubes are what make headers work." Please tell me if I have misread "tubes are what make headers work" and have misinterpreted your point--and if I have, then what your point is.

My point is that gas molecules don't know or care about how the structure they are flowing through was put together (cast, extruded, rolled and welded, blacksmithed over a form and forge welded together, or drilled.) Shape and size are everything, and the ideal shape and size CAN be achieved with a casting and without tubes. It's just not practical and it wouldn't sell, and that is why it isn't done. Tubes are easier and cheaper in the case of an optimized exhaust manifold/header, so that is what they are made of.

Maybe your huffiness and belligerence caused me to miss your point. If I have missed your point, maybe try making it without those things. It's worth a shot.

**I can edit in additional comments, too. I'm not trying to change the laws of physics; I am trying to explain them. Work on speaking/writing with more precision and accuracy, and the understanding of others will naturally follow.
 

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Discussion Starter · #13 ·
While your at it do research on the best flowing mufflers because even though flowmaster claims to be the best they are far from it in flow technology. I will not offer a best or worst opinion as you should do your own research to make your own opinion. They do make them to flow well and still not be loud. Mark
Also true. In the video I linked above, David Vizard says that in order for a muffler not to cause a restriction, it needs to flow 2.3CFM for each open header horsepower of the engine. Not all muffler manufacturers will give you CFM ratings of their mufflers. You can assume some things with straight-through mufflers based on what a tube of the same diameter would flow. Dynomax seems to be pretty good about rating their mufflers for flow in CFM, but who knows how honest they really are and at what pressure (or vacuum) they are testing them at?

I have to say that I like the sound of a Flowmaster, but I wouldn't touch one with a ten foot pole (or ten feet of exhaust tubing?) Back in my VW days, Techtonics Tuning, one of the big VW performance parts suppliers, switched to FM mufflers. This was before I could craft my own exhaust systems exactly to my spec, so I bought a system with a FM. THREE times I broke an internal weld in the muffler, causing it to buzz. Three times I had to remove the muffler and get another.

Vizard trashes FM mufflers in that video, and for good reason. FMs are for sound, not really for performance. They might well flow better than stock, but not well enough. I would rather use a straight-through muffler such as a Magnaflow or a Borla, or just use a Super Turbo muffler for more hush. He trashes Supertrapp mufflers in the video also. He's hilarious, in part because he doesn't say or do anything that isn't empirically learned from the flowbench and dynamometer. If you argue with him, you're basically arguing with a dyno.
 

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Discussion Starter · #15 ·
I have been using summit fully welded turbo mufflers for years , they flow well they sound good and they are cheap. The only thing I do is hit them with high temp paint to make them last longer (rust) No clue as to the flow on them however they are strait through with a baffle inside to bounce the sound around to lower the volume. That is what is going on my 89. I hope to make my exhaust much better in the future but for now its a 3" single.
I have never had much luck with high temp paint sticking to mufflers and exhaust tubing. Something is better than nothing, I suppose.

I will probably TIG weld everything from 304 stainless steel downstream of the headers/manifolds. I know that is not an option for everybody, but it is for me and I would prefer to do this only once. Of course, how long a stainless muffler core will actually last is anybody's bet, but I can make those removable instead of welding them in.
 
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