Byggandet av "shorty" headers...
Det är på engelska pga. språket på det andra forumet jag var medlem på. Jag kommer dock att översätta det inom kort.
First of all, you buy a set of these (or similar):
The ones who have read my project thread recognise these...
The headers that can be used for the B6304 engine are the M50/M52 BMW engine headers (1992-1998 I think).
Start by cutting the head flanges off. Some headers may have a design where you can actually re-drill the flange to fit on the B6304, but not this one.
If you are keeping the BMW head flange, then there is also a question whether or not the opening in the BMW head flange have a smooth transition where it meets the runners. In that case you may have to port it, or even add material and then port it.
After the flanges have been cut off from the headers, we clean it up a little.
The headers in question are designed to fit the stock exhaust system of a BMW M3, and therefore the flanges and pipes are designed based on that. So we need to change more than just the flanges.
On this specific header, each of the three primary runners have a cross-sectional area of 962 mm2. For one header that makes the three primary runners have a combined cross-sectional area of 2886 mm2. That means that the collector of each header will need an output size of roughly 2.4".
But the collector tapered down to a pretty small size, and it had an outlet with a cross-sectional area of 1735 mm2. So I cut the tapered part after the collector off, and I will be replacing that part with 2.5" pipe (cross-sectional area of 3167 mm2).
Measure the collector part, and cut it where it tapers down. In this case it started to taper down from a size of 2.5" which is perfect for me to weld my secondary runners to (2.5" pipe).
Then clean it up a little:
This is how the 2.5" pipe is going to sit (not neccesarily at that angle though). I can't fit any pipes to the headers until they are test fitted on the car.
The pipes will not be welded directly to the headers though. I will use V-band flanges for that.
Here you can see that the collectors are tapered down a lot to fit the stock BMW output flanges, and that they are restrictive and have a flow imbalance:
Cut the Volvo head flange in two pieces.
There are two reasons why: To minimise the warping, and to be able to work on each header individually.
Please observe how it has to be cut so that the exhaust gaskets fit, and so that both headers can be put on the head with the correct amount of nuts.
This flange is the stainless steel version.
Weld the flanges to the headers. I MIG-weld using stainless 0.6mm wire and CO2 as inert gas.
I built up a lot of material with the welder to be able to port the opening out later on.
Unshrouding the bolt holes will be neccesary as well since some of the runners are really close to the bolt holes.
Welding it on both the inside as well as the outside is dependant on the header design you have chosen. On this header design I didn't have to weld it on the inside. I just wanted to know how difficult it was to do it with a MIG welder.
Then port it as much as you can.
Use a really good tool for this part. Use any technology and design of the tool you like, but investing in good equipment pays off in the end. It will take some time, even with good tools.
And then clean it up.
It looks like these headers will flow pretty good :-D
This is what they look like when almost finished.
I need to test fit them to the car and then put the secondary runners on.
The flanges will have to be machined flat. Some straightening of the flanges has to be made first, or else there will be nothing left after machining.
To do that properly, you need one of these. An 8kW induction heater:
And then clamp the headers to some really hard (and flat) beams. Heat them in strategic places and clamp it as hard as you can. Let them cool off by themselves, and then you can remove them:
Then the headers are left to Alex Buchka to be machined flat, and to get the V-band flanges welded on.
Really nice work :-D
Remove the stock manifolds and the downpipe/cat section:
Since I will get a new performance exhaust system, the rest will have to go as well.
It is very hard to get the entire system off the V90. I had to cut it in several places.
Test fit the headers.
Three problems arose...
* The headers got too close to the engine, which made the V-band clamps impossible to get on and off the flange.
* Both headers touched the water pipe that runs behind the stock manifolds.
* The front header touched the engine mount.
The first problem is easily fixed. Another head flange (10mm thick) is ordered. Then use that as a spacer to get the headers out. With exhaust gaskets between the head and spacer flange + exhaust gaskets between the spacer flange and the headers, the total spacing from the head is 12.5mm. That is enough to get the headers fitted.
The second problem is not easily fixed though. I massaged the pipe a little to bend it out of the way, but both headers are still touching it a little. Will this be a problem?
The third problem is fixed somewhat easily. Just cut a piece out of the engine mount.
:-P or :wtf: ? You decide.
Then test fit the secondary runners. It takes some patience to get this to fit properly. They have to clear each other, the floor of the car (while still sitting as close to it as possible), the chassis bracing etc. etc.
In total, I ended up using one straight 1000mm long piece, three 30* bends and two 45* bends.
Spot weld it all while it is fitted to the car, and then take it down to inspect it.
Remember that when you spot weld it in place, then put the welds 180* opposite of each other on the pipes so that it doesn't warp.
Then weld it all up.
Remember to still use the same procedure as when you were spot welding it while it was fitted to the car. Always weld on the opposite side of where you last welded on the pipe.
If you are using V-band flanges, then leave a small piece of the pipe protruding through the flange. This is used as a labyrinth gasket and it seals better. That way you will probably not need any type of gasket.
Then I put on a temporary pipe to use on the way to the exhaust shop where my new system will be fitted.
"TA BORT" as written on the temporary pipe, means "remove" in English.
I recommend you not to do what I did. It is incredibly loud! But I didn't have a choice really.
This is what it looks like from above when almost finished.
And when everything is put together (with a spacer flange and all the exhaust gaskets), and it has been taken for a spin to see if everything is alright, it looks like this.
Hot, hot, hot...
