false alarm

[bravekozak]

This eBay Netherlands listing caught my attention.
I know it's not for our engines, but since he said its in its original box and its stainless, then maybe Megan Racing might make one for the Mazda B6 engine.
Unfortunately not.

[Rocketman]

Are you looking for a long tube header for a B6 DOHC?

[bravekozak]

long tube

I presume when you say long tube, you mean so that it joins the remainder of the exhaust system past the catalytic converter? If so, yes.

[Aaronbrook37]

I propose another solution. Cliffnotes at the bottom for those who prefer pictures and or ignoring me.

It seems like a lot of time and R&D is being put into adopting 4G63T exhaust manifolds and B16 intake manifolds, especially for the B6T and BP-T crowd. Why haven't the naturally aspirated folks looked into something like this?

The notion of an uber-long header that joins past the catalytic converter is foreign to me. However, one that joins past the oil pan is not. Let's take a look and see if I'm going too far out on a limb here.

D15/D16 Exhaust Manifold Gasket


B6 SOHC Exhaust Manifold Gasket


Anybody with a set of eyeballs will see that there's some work to be done to get compatibility. Short-tube/OEM swaps are a no-go. No leverage, and far too much in terms of modification.

Similarities:

Both are SOHC OHV small-sized 4 cylinders motors with peppy and economical motor bases. The Honda heads unquestionably breathe better than their SOHC (and probably DOHC) counterparts... the motorcycle legacy lives on in the fire-breathing flow capabilities of Honda motors. A D15/16 has roughly the same engine size give or take a few CC's, but also higher compression I would venture to guess.

Differences:

Short-tube headers are a no-go. They're too tight to work with, given the differences in port spacing and structure. That one fellow got the Megan Racing 4G63T manifold working, but I'm sure it was far from easy for him. So where does that leave us in trying to help BK get a nice sexy set of pipes for the B6.

Take a long tube header-set:



Remember, you can pick these things up for under $50 on Ebay for the super cheap ones. That's not to say they're high quality or reliable or safe, but just that it'd be a fantastic experiment to really... open up (pardon the pun)... the SOHC manifold market round these parts.

Some here would advocate using heat and high pressure tension-bending to get it to shape, but that scares me, especially with thin-wall stainless coming from Ebay. Here's what to do:

Chop the flange, and clamp the center pipes closer together with force and care. In a vice and with some convincing, this shouldn't be too hard - thanks to the long-tubes. Check the height of the runners, and reduce if necessary. Likewise, clamp and adjust the port shape to reduce ovalness and increase circular shape. Port B6 flange to reduce restriction and maintain specification within the limits of the gasket. Head could probably use some as well while you're there. Tack-weld to shape and form it to fit with the angle and curvature of the catalytic converter.

Weld it all up solid with a quality welder, and get some new/refinished hardware for it. Wrap or ceramic coat to your heart's content and enjoy the rip-roaring sound of SOHC madness.

Too long; didn't read: Why not just chop up an Ebay D15 manifold and work it to spec, BK?

[bravekozak]

B6 flange

This is the most interesting reading I have done in quite some time.
Does anyone have a picture of the B6 flange? I would like to see how much bigger it is than the gasket. Also, what thickness is the flange?
I could get a B6 flange waterjet cut for cheap.

[Aaronbrook37]

The MX-3 chaps say that the flanges between B6's are the same between SOHC and the DOHC motors. VERY IMPORTANT THOUGH TO MAKE SURE YOU HAVE A LATE B6 MOTOR FROM 1990+.




The roundy oddball is the bad one from the early B6's, and the flat/oval one is the one that could be Honda-adapted I think. Seems like less bending than intended for the late manifolds.

Here are some pictures from the venerable Matt/Rocketman of his XR2 head/exhaust manifold. These will match the late B6 motors. Nothing directly of the flange, but it's useful for visuals and getting some creative juices flowing. Seems like the ports are less oddball than I expected.

http://www.werbatfik.com/img/capriwork/capriwork10.jpg

http://www.werbatfik.com/img/capriwork/capriwork51.jpg

http://www.werbatfik.com/img/capriwork/capriwork147.jpg

http://www.werbatfik.com/img/capriwork/capriwork185.jpg

http://www.werbatfik.com/img/capriwork/capriwork188.jpg

http://www.werbatfik.com/img/capriwork/capriwork211.jpg

I'm still brainstorming on a better solution for the B3 flange and early B6. We need an easy-to-produce long-tube header with rounder ports. The inner-runner bending is definitely a must for these... might be able to get away without it if the port spacing is pretty good between the late manifolds and the Honda ones. For this round early port, Toyota comes to mind:

1.8L Celica / Corolla Header:



Scion TC Header:

[Aaronbrook37]

All we really need is a good set of schematics and measurements on both the early b6 and late b6 flanges to get some port sizing and spacing, and then plug it in to the Honda data accordingly. Anybody willing to scan a few gaskets they have lying around? Here's what we need scanned:

B3 Festiva Exhaust Manifold Gasket
Early B6 Exhaust Manifold Gasket
Late B6 Exhaust Manifold Gasket

We obviously need these blown up to 100% scale so that measurements can be taken on them. Any volunteers? Tracking down some Honda ones will be a shlep I think unless someone wants to pilfer some from a junkyard and scan em up for us.

Related reading/adaptation:

http://www.cardomain.com/ride/552384/1994-mazda-mx-3/page-6

It's a Probe 2.0L Header adapted to a B6 DOHC.

[Rocketman]

My pics are from a B6T which also has the same flange as the N/A B6 DOCH (B6D?) How much do these differ from the later style dohc in the MX3? I thought the head/intake manifold were different, but the exhaust stayed the same?

I was going to suggest the redrilled 2.0L probe header, as I've seen that before. IIRC Corksport also offers a header for the DOHC

[Pu241]

Aaronbrook37, B3 exhaust manifold gasket scanned where do you want it sent to?

[Aaronbrook37]

My email address if you don't mind. For spam purposes, it's my username without the 37 and with @gmail.com on the end. Thanks good sir for your contributions!

[Aaronbrook37]

Many thanks to John for his B3 gasket contribution. I've printed it out on 8.5x11 without adjusting or scaling it... so hopefully it's to size. Looks about right though. I'm gonna trace it and get some schematics going on spacing, sizing, etc. From there, I begin my quest to the land of Hondas and Toyotas to find a suitable donor gasket for long-tube header production. This exploration brought to you by Sasquatch Racing. Stay tuned folks... race SOHC headers ahoy!

[Pu241]

Aaron, please measure the printed B3 gasket across the bottom 4 bolt holes at its maximum width (out side edge of the gasket bolt holes).
The actual gasket is 11 and 5/8" (wish I had an accurate mm scale that large).
If they do not match then another scan/print out at actual size maybe necessary.

[Aaronbrook37]

Yep - 11 5/8ths. Thanks John! I've already started a lot of the math and calculations to try and find us a good solution for port sizing and spacing. Will keep you all posted with what I come up with when I can muster up some time to get some higher quality graphics and calculations going.

[sasquatch]

the only problem with cutting the flange and making headers for the b3 from lets say a d series honda is that to but them they are about 100 bucks or more... my header that i made only cost about 40 bucks in metal... if i had made the collector better it would have been awesome... and really it probably less work to make a new one that mod a made one cause your most likly gonna need to mod the rear bracket to hold up the back so it wont crack...

im really wanting to help out and make some performance parts for festivas... what would sell better? a turbo manifold for the b3 or a N/A header?