Help with custom headers

[Sid_RallyX_82]

My Festi has the B3 and 5sp in it. Not sure how long I'm going to keep them, but I would like to help them out a bit by doing things such as building an exhaust to swap on for track days. I can fabricate, weld, and bend tubing, so it should be pretty easy for me... Right? I think I want to peak my torque at around 3.5k-4k and keep most of the power up top, so, I've been looking around the old inter web and these "Header Calculators" say my primary tubes should be 35"x0.71id. That really doesn't sound right to me. Does anyone know any tried and true dimensions? Also, any tips on preventing reversion? And, what are the benefits of 4-2-1 and 3Y? If any of this is dumb and I just shouldn't bother, let me know

[jdobbs86]

IMO nothing that catches your interest is dumb and you should always bother. I don't have all that much additional info for you but .71in is not terribly surprising to me, 35in seems on the long side but what do i know.

[gergorian]

I have a long tube header from Matt Dickmeyer on my B3 and I wouldn't be surprised if the primary tubes were 35" or longer. I'm not sure about the diameter though.

[bhearts]

Matt's header was 1 3/8 inch

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[bhearts]

It is a 4 to 1 with a 2 inch output, right?

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[bhearts]

You'd probably be better off with inch and a quarter id exhaust though, unless you plan on adding a supercharger or rear turbo or something, in that case 1.375 is room to grow.

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[gergorian]

It is a 4 to 1 with a 2 inch output, right?

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yes it is

[Advancedynamix]

.700 primaries won't work on a 1300cc 4 cylinder. Are you sure you input the correct number of cylinders? That sounds like the primary diameter of a 1300cc V8.

[bravekozak]

My B6 cylinder head is 1.25 in and 1.25 out.

[jdobbs86]

This is me when I don't sleep well :spam2:

[Sid_RallyX_82]

I don't think the calculator I used asked for number of cylinders, so it may have assumed v8.

[Sid_RallyX_82]

So, looks like the suggestion is somewhere around 1.25-1.375id, what about configuration? Could someone lay out the Pros/Cons of EL/UEL 4-1, 4-2-1, and tri-y? As far as I can figure, some try to act as multiple length tubes in one and provide scavenging effects, but I'm still pretty new to tuning...

[bhearts]

You can't go wrong with a 4-1 that's longer than it needs to be, 30+ inches. Obviously a 4-2-1 will have multiple torque peaks, but simplicity sake, I'd stick with 4-1. Plenty of other car groups have plenty of great luck with equal length 4-1. Until you have your engine breathing to it's max, having a header fine tuned to a precise length isn't a huge deal, but anything with quality merge collectors is going to provide enhanced flow over those factory manifolds.

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[Advancedynamix]

4 to 1 will provide higher peak TQ numbers, depending on the tune length. Try y will give a more broad peak TQ area. Honestly though, the stock setup on these engines is so far from optimal, that it's very easy to make an improvement. A try y with 16" long 1.25" primaries and 21" long 1.75" secondaries, collecting into a 2" pipe for 36" would be about perfect for a 1300cc 2 valve car engine with a target TQ between 3000 and 5500 rpm.
Most low volume, budget minded header builders will stick to a traditional equal length 4 to 1 because it's the best bang for the buck. Collectors are the most difficult and expensive component in a header, and having 3 of them can drastically increase the cost of the header. Check out "Burns Stainless" website for an example of the commitment that goes into a good collector and you'll see why the value is in the 4 to 1 merge. If you were to use Burns collectors to build a try y you'd have 450 dollars invested in just your collectors. I often use Burns collectors when making 1 or 2 headers because it's cheaper than building 1 or 2 of my own collectors.

[bhearts]

4 to 1 will provide higher peak TQ numbers, depending on the tune length. Try y will give a more broad peak TQ area. Honestly though, the stock setup on these engines is so far from optimal, that it's very easy to make an improvement. A try y with 16" long 1.25" primaries and 21" long 1.75" secondaries, collecting into a 2" pipe for 36" would be about perfect for a 1300cc 2 valve car engine with a target TQ between 3000 and 5500 rpm.
Most low volume, budget minded header builders will stick to a traditional equal length 4 to 1 because it's the best bang for the buck. Collectors are the most difficult and expensive component in a header, and having 3 of them can drastically increase the cost of the header. Check out "Burns Stainless" website for an example of the commitment that goes into a good collector and you'll see why the value is in the 4 to 1 merge. If you were to use Burns collectors to build a try y you'd have 450 dollars invested in just your collectors. I often use Burns collectors when making 1 or 2 headers because it's cheaper than building 1 or 2 of my own collectors.

Especially if you want parallel entries. Relatively cheap if you just just straight pieces for the merge, but otherwise you're cutting up bends to get your merge. I'd buy too, those guys know what they are making. I shop at Columbia river mantel bends, they will also have the pipe you need.

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