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Old 04-20-2012, 08:53 PM
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Primary length

So I found out that the headers (from bbk made for a ford modified to be used on a sbc d port) yes, are indeed equal. Albeit they are 17.5 inches in length, the primaries that is. According to the length equation from "headers by ed" {(CID * 1900)/(rpm_max * tube_od2)} the recommended length is 34.2 inches.

This being said, what is going to change in using 17.5 inch primaries vs 34.2 inch primaries aside from a higher exhaust note?

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Old 04-20-2012, 11:55 PM
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The short primaries will push the power peak upwards, your formula will tell you that. What is the primary diameter? Being that short, I doubt they'll perform any better than a set of shorty or block hugger headers. What do you want to use them on, I can't see how these headers will even fit a doorslammer, is there even enough length to make the 90 turn to aim them out the back? What is the diameter and length of the collector?
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Old 04-21-2012, 06:39 AM
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Bare with me on this because this is something I know very little on, exhaust that is.

They are 1 5/8 primaries, the diameter of the collector is 2.5 inches, the length I haven't a clue.

What do you mean by a "door slammer"?

Link to the bbk headers.
http://www.summitracing.com/parts/BBK-1529/

I will be changing the port end of the headers to work with a sbc. I'm not a ford guy, the blocks are too weak for my taste.
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Old 04-21-2012, 06:53 AM
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To fitment, pics of them in a mustang.

http://customerpics.americanmuscle.c...011.php?sort=1

http://www.allfordmustangs.com/forum...e-p1010125.jpg

Pictures of a used set from a forum
http://www.hardcore50.com/vbulletin/...ad.php?t=51387

I would have to make a down pipe of some kind. I would be bringing them down to an x pipe to spintech sportsmans to exit out the side.

This exhaust vid sounds 100% perfect to me, albeit its on a mustang. This is the goal of the setup, in that it sounds as close to that aside using a 5.0 block.
http://www.youtube.com/watch?v=XcH7kdVgro0

Last edited by blight; 04-21-2012 at 07:09 AM.
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Old 04-21-2012, 10:36 AM
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good luck with that
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Old 04-21-2012, 11:27 AM
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Quote:
Originally Posted by blight
Bare with me on this because this is something I know very little on, exhaust that is.

They are 1 5/8 primaries, the diameter of the collector is 2.5 inches, the length I haven't a clue.

What do you mean by a "door slammer"?

Link to the bbk headers.
http://www.summitracing.com/parts/BBK-1529/

I will be changing the port end of the headers to work with a sbc. I'm not a ford guy, the blocks are too weak for my taste.
I'm going to save you ~$250-$300 and a hundred hours of wasted labor: Buy a set of headers made to fit the engine/vehicle they're being used on and call it good.
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Old 04-21-2012, 08:25 PM
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Completely custom car on a rotisserie right now, that part doesn't matter.
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Old 04-21-2012, 08:57 PM
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Quote:
Originally Posted by blight
Completely custom car on a rotisserie right now, that part doesn't matter.
OK, another option is to buy a pair of header flanges, various bends and straights and fab up a set to fit. Build it yourself header kits are also available, as are flanges w/the header stubs already welded on.

But the MAIN point is, starting w/a Ford header is not the way I would recommend anyone go about this. What you are proposing is going to be a real chore w/no guarantee of a good outcome- nothing like adapting a BBC header to a Cad engine, for example.


BBC headers compared to a 472/500 ci Cad
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Old 04-22-2012, 06:40 AM
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I completely understand that. I appreciate the advice, and I have considered that. I would be using the bbk headers as a BASE they would be cut up as hell by the time I used them. I may try to set of used ones and use that as a base so that I can know how to route the ones I make.

Btw what would you advise on doing about coatings? From my understanding just coating the outside is pretty pointless if one doesn't coat the inside. I have been told there is a way I can do this myself. What would you use to coat the inside?

Also just for future reference. I am currently working for anderson and dahlen, so metal fab is something I don't shy away from in the slightest. I am just a little uneducated as to the thermodynamics to exhaust. Albeit I am sure there are a lot of people that don't know much seeing that I have searched, and searched, and searched and I have had a jumble of different "opinions" and very little "here is the equation to figure X out". So I really do appreciate the good information given here.
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Old 04-22-2012, 08:38 AM
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Quote:
Originally Posted by blight
I completely understand that. I appreciate the advice, and I have considered that. I would be using the bbk headers as a BASE they would be cut up as hell by the time I used them. I may try to set of used ones and use that as a base so that I can know how to route the ones I make.

Btw what would you advise on doing about coatings? From my understanding just coating the outside is pretty pointless if one doesn't coat the inside. I have been told there is a way I can do this myself. What would you use to coat the inside?

Also just for future reference. I am currently working for anderson and dahlen, so metal fab is something I don't shy away from in the slightest. I am just a little uneducated as to the thermodynamics to exhaust. Albeit I am sure there are a lot of people that don't know much seeing that I have searched, and searched, and searched and I have had a jumble of different "opinions" and very little "here is the equation to figure X out". So I really do appreciate the good information given here.
The point in coatings and such (for performance not just looks) is to keep the heat (and velocity or energy) inside the system and not let it pass into the air that the engine uses. So whatever can be done to enhance that will help. Cool air to the carb is probably as much help as any sort of header coating or wrap, but it all adds up.

I remember seeing a company (the name escapes me, and there may be more than one company) that would coat anyone's headers w/a ceramic type coating, inside and out if requested. This company also sold headers.
I think the headers needed to be unused, or possibly that's what was preferred for the best results. Now, whether having multiple welded joints would affect the coating durability I'm not sure- but obviously the best results would come from smooth, clean tubes in and out. IIRC it was not cheap.

If the headers were made from stainless, the coating wouldn't be necessary for anything except heat retention, and that could be done w/an external header wrap, being as how a SS header won't rust the way mild steel wrapped headers are said to (I've never wrapped a header, so I cannot say).

There are a bunch of calculators here. Among them is one for header tube length and diameter, but I think you found one for that already.
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Old 04-23-2012, 08:41 PM
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I found this;
http://forums.hybridz.org/index.php/...metic-for-you/
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Old 04-24-2012, 08:08 AM
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