stayer

Hi friends!
In this topic I want to talk about the headers. I don't know English. I understand what it was, what kind of things are discussed. But I do not understand why the exhaust manifold is called the "header". My translator translates this word as a "title".

Well. All people (tuners, builders) can be divided into two groups. One group is large, it includes 95% of the people. Just call them - tuners.
The second group, with an engineering mindset and design approach. There are not many, not more than 5%(maybe less). Let's call them - engineers.

What distinguishes a tuner from the engineer? The tuner builds the engine (or anything) from what is on sale. That is, it does what happens (good or bad). He wants but can not.
The engineer has a different approach. It collects the engine the way he wants. That is, if not there are some items in the sale, or there is a detail, but it does not meet the desired parameter, then the engineer makes this detail. At the same time, he gets what he originally intended, and not what you can buy in the store.
In this topic I want to talk about the exhaust manifold (header). I want to show the engineering approach. It will be as always very interesting and informative.

stayer

So. First you need to understand that there is a sale, and whether it was easier to buy? I proceed from its own realities. For example in my country it is almost impossible to buy the RRE headers. Headers DNA I don't need a brand. Still have OBX headers. Our users are split 50: 50 (bad is good) Other brands for the 4G69 I don't know. China is not considered.
So, in my case, it is necessary to make a header from scratch. On the one hand it's bad (it's a long, expensive, etc.) But on the other hand, I can implement whatever I want.

stayer

Well, here we go. Sometimes it is necessary to work not only his head, but and hands. I want to implement a few details in this project. For example. After the cylinder head is formed of the regiment. That is, the diameter of the pipe for the header, is always greater than the diameter of the hole in the cylinder head. This is done to improve scavenging cilinder. The exhaust gases freely out of the head. But when there is a reverse wave, they were difficult to get into the cylinder.
View picture.

What I want to do? This is the exit from the cylinder head. If the inside of the header to extend the pipe, it will complicate the ingress of gases from the backward wave. The cleansing of the cylinders is improved.

stayer

For production I need to buy some items. I'm going to scrap metal dealer and buy it.

It's parts are made of stainless steel AISI 304. The wall thickness of 2 mm.
Inner diameter is selected in the following manner. You have to calculate the cross-sectional area of the exhaust seats at the narrowest point. Multiply by 2 valves. Get the area of the inner section. It is impossible to do less than that would not interfere with the exhaust. And do not do a great. This decreases the flow rate.
In my case, the cylinder head has ports. Valve seats of large size. Internal pipe size should be 38 mm. Now you understand why the stock exhaust such a narrow pipe. Everything is correctly done and calculated.

stayer

The stock header is fixed at the bottom of the engine block. It is necessary to prevent the load on the studs of the cylinder head. My header will also be pinned to the bottom.
For this, I laser cut this part.

In order to realize what I'm doing, I need to carve 4 of these here parts.

stayer

When all parts purchased, you can begin to assemble. Still need the straight pipe (6-7 feet).

I don't know how to call in English this part? In Russian it's the shutter.

stayer

All four shutter ready. Now the exhaust gases will be much harder to get back into the cylinder.


Can be welded to the flange. Be sure the flange bolted to the cylinder head. Otherwise it will curve as a Turkish sabre.

stayer

This is followed by the Assembly of the header.



I want to say. Pipe lengths are all the same. You can see that pipes of different lengths. But it is not. In the engine 4G69, channels inside the cylinder head are of different lengths for all cylinders. If you measure from the exhaust valve to the end of the pipe, all the dimensions are the same. This is important.

stayer

At the bottom of the pipe welded together from the inside.

Next to exhaust manifolds install the cone and flange. However, this is not entirely correct. The exhaust gases will be released into a single volume. At the same time they will interfere with each other. We need to make a so-called ejector. Can find Wikipedia, what is the ejector. This is a jet pump. Which is due to the speed of the jets of gas will increase the speed of exhaust from other cylinders. That is, all cylinders will be pulling vacuum, and gases. Each next cylinder to repeat the cycle.

stayer

To get started in the cone is 4 cut.

Next, make a cross of stainless steel. But not to weld.

This cross must be welded between the pipes.

stayer

Now we have to make the part in the form of bullets. For this I cut a piece of pipe into 4 pieces and flip over.



It is necessary that the sharp end went into the narrow part of the cone. Later I will take a video to show how work the ejector.

stayer

You can now install the cone and brew all the seams.

stayer

Is then welded to the lower flange.

stayer

A draft of the exhaust manifold is ready.



Next up is finishing. Grouting and sandblasting.
After production of the necessary pressure-tested the exhaust manifold. It is necessary to raise the pressure to 85 psi. And put it in the bath water.



This will allow you to find all the cracks and micropores. I found 6.

stayer

After restoring integrity, can be sent to a sandblasting chamber. It turns out this product.