Exploring the SAI passages

From pcarworkshop

Okay, in this article we will be exploring the inner depths of the SAI passages. Its actually a pretty simple system except its loaded with turns and twists (yes, pun intended). I thought I would try to capture this while I am cleaning out the old passages...

So I tried to mockup what the SAI total route looks like on the table top. Here we have the two banks of heads with the cam carriers attached. The position of the heads are the same as if you are looking into the engine compartment with the hood open, i.e. Piston 1 is the left front. The air pump is mounted under the manifold and is connected to both cam carriers via piping. The intake of the air pump is just behind the air filter. The air is run through the rubber hose into the pump. The pump output goes through a one-way valve and into a splitter. We will see this in the next picture...

This is the view from the back of the engine. The pump feeds into a splitter which directs air into two tubes, one for each cam carrier.

Here is a closeup of the splitter...notice the left hand feed pipe is connected to the top of the cam carrier. Inside the cam carrier is a cast distribution tube that allows the air to be directed to each of the exhaust ports.

Here is the left hand bank. The air tube runs just ahead of the back sheet metal to the back of the cam carrier on the rear of the engine.

So here is a cam carrier off the car. I put some stiff wire into each SAI port so you can see the angle of the drilled hole....on both my carriers the rear-most ports were almost entirely plugged...its a bit curious that both sides are the same.

Okay, here are some closeups of the each of the air passages. This is piston 1, ie the one the farthest away from the air source. Notice the cast passage that runs from the access hole to the access tube that runs parallel to the valve cover.

Piston 2, similar to Piston 1.

Piston 3, rear most. You can see the threaded access hole on the upper right corner. The castings of the access tube can be seen clearly on the corner of the casting.

Here are the heads with the same stiff wire showing the angles of the SAI ports. On my heads they were actually pretty clear all the way from the top to the base of the cam carriers.

Looking from the top you can see the angle difference between the SAI tubes in the heads vs those in the carriers. Since they are connected together the air actually has to change angles in mid stream as it travels from the top of the cam carriers to the exhaust port.

Two of my ports were quite plugged so I used a small drill but to cleanout the crap. Quite a bit of carbon was carved out with the bit (with no metal). The material is a hard carbon material and actually loaded the drill a bit so it was very crusty and hard.

Here is a clearer shot...

I then cleaned up the outside portion with my drmel tools and a very small bit..again the carbon material is very heard!

And then with a liberal use of brushes to cleanout the access tube...again lots of black carbon gunk....

After cleanup here is that the tube looks like that runs inside the cam carrier.

And nice clean ports............

Links to Rebuild Tour

1. Getting started, dropping the engine and superficial stripdown
2. Checking the default timing and Cams
3. Looking at the heads and the SAI passages
4. Valve guides, valves and carbon
5. Further Dissassembly
6. Exploring the SAI passages
7. Cleaning and getting ready to put it all together again
8. Rods and last minute checks before putting the case together
9. Sealing the case (or tomb)
10. Putting the pistons/cylinders back
11. Camshaft timing Part I
12. Camshaft timing Part II
13. Messing up a clean looking engine
14. Not quite there
15. Cranking it up