 | CAUSE:
If you have found this site, you are probably aware of the problem some of the Vauxhall C20XE and C20LET GM heads suffer from, commonly known as the `porous head`. The following pages will hopefully help you understand the problem and possible fixes.
Cause - Click to read up about one of the most common cause of `mayo in the water` on the C20XE and C20LET engines and the misconception that is the porous head.
FIXES:
Outlined are two guides which will help you understand how to fix the problem of the `porous head`.
Solid Tubing - Click to gain an insight on how to use a solid tubular bar to solve the problem.
Hollow Sleeving - Click to gain an insight on how to use a hollow tubular sleeve to solve the problem.
Pipe Size - As a guide the size of pipe which a few people have reported using is: 8mm in diameter and 87mm in length. I would sugest using an aliminium tube where possible so there is no cross metal corrosion, and no warping due to different expansion rates. See the visitors section for links to sites which maybe using / detailing the fix.
| | | |
On this page we will try to show you what the problem is and where it occurs. We would suggest you read both the Solid Sleeving and the Hollow Tubing pages, these will help make sure you understand what the problem is and where it occurs! One of the best things that will help you see the problem is pictures taken from a sectioned head (cut in half C20XE head) - a big thanks goes out to Gary Poole for cutting up his head, and allowing us to use the pictures.
Let's get started:
The first thing you need to understand is how oil travels round from the engine and through the head. The picture below shows (in the red box) the oil riser, and the head bolt hole (where the head bolt screws into the block). Oil is sent upto the head using the headbolt hole in the head:
In the following picture of a head cut in half, you can see all the important oil ways in the head.
- The two head bolt holes A, one of which is used to supply oil (when the head bolt is in palce it will cap off the hole, hence no oil leaks out)
- The two water paths B, these run the length of the head, but it is this section where the oil passes into the water. You can see the missformation where the weakness occurs (all will become clear).
- The centre oil gallery C, this runs from the front of the head to the back, it is connected to the cam oil galleries(D) and the headbolt (A) hole to supply oil rising from block to the cam's. The front of this gallery (on the right in the picture) is blocked off by a grub scrw found on the front of the engine, between the two centre exhaust ports.
- The cam oil galleries D, these run from one end of the head to the other, there is one for each cam. These get oil by it rising up the headbolt, passing into the centre oil gallery, and passing upto them (the paths that leed upto them are caped with crub screws, these can be found under the cam cover).
In the following picture you can see, if you look very closely the crack where oil passes from the centre oil gallery into the water gallery. Click image to enlarge
Ok so now you know where the problem occurs and what the problem actually is. It is beleved that the crack where the oil passes into the water is often caused by people over torquing the head when refiting it. However I have heard of the problem occuring quite randomly i.e. the head hasn't been off. I have seen it happen after refitting the engine to a new car. So there is no real reason why it would crack, bar the weakness in the metal where its at its thinest.
If you are still not quite clear on the problem, the following two pages will hopefully give you an idea how you would fix the problem and clear up any questions you may have.
Solid Tubing - this involves inserting a block, and rerouting the oil.
Hollow sleeving - this involves inserting a hollow tube to allow the oil to flow through, avoiding the crack.
If you believe you have a porous head, and you want someone who has done the fix before, check out our Services page, it has links to people who can help, you maybe supprised at the price too!
Please read the Disclaimer before trying anything on your own head!!
| |
.jpg)