dangonay

Finally got down to working on my heads (planning a wedding takes a lot of time).

Removing the valves is going to be a little difficult considering how far down in the head the retainers are.

<img src="http://pictureposter.audiworld.com/19185/intvalveret.jpg">

Here's some help from Snap-On...

<img src="http://pictureposter.audiworld.com/19185/valvecomp2.jpg">

A while back I remember reading a post from someone with a 1.8T who had to replace their head because a valve guide went bad and they weren't replaceable. If you're reading this, please respond with any comments you may have.

These 2 pictures are from one of my 2.7T heads. Now, many people have said that porting & polishing a 2.7T head is a waste of money since the heads flow so well. I like to rebuild things from the ground up, and since I'm a mechanic, it's not really costing me anything except my time.

Here's what I found inside my head. You can see some very rough edges just past the valve seat where there has been some obvious machining done. It's not as obvious in the pics, but there's a definite "lip" where the metal has been pushed or folded over. I would think this would be detrimental to smooth intake charge airflow. So, this is one thing I'm going to remove when I start porting my heads.

Now the questions:

1. Are the valve guides replaceable on the 2.7T heads? They look like they would be.

2. Has anyone else rebuilt their 2.7T heads, and if so did your valve seats look like mine?

3. Has anyone here ported their 2.7T heads?

I'm familiar with rebuilding engines, but I haven't done anything with Audi 5 valve heads, so I'd like any info I can get before I start.

<img src="http://pictureposter.audiworld.com/19185/intport1.jpg">

<img src="http://pictureposter.audiworld.com/19185/intport2.jpg">

Mike O.

...I'd only be worried about messing up the seats if I was going to get in there to machine/polish things. Yeah the casting looks a little rough but I don't know how much gain you'll get polishing that.

Hey, if you've got the time do it. As long as you try to replicate your effort from port to port, I don't think you'll end up worse off.

Mike O.

1 slow Audi

dude if you dont know how to port or ported one or two heads dont even start cause you will cause more damage than good.When I started it was on old cheap cars and parts were widely avaliable and cheap so I wasnt woried.Im not saying its a waste of time cause its not but be very carefull and if its your first take it to a profesional.
ps: dont try to port big cause its not only the size of the port that matters.
good luck

MikTip

You can "smooth" the machine work behind the valve seats.

What do the intake ports look like? Picture?

xr4tic

Just be VERY careful not to nick the seat. Ideally you want the bowl sides to flow right into the seat, but you want to remove as little material as possible (you want to keep the bowl rough, not smooth, on the intake side)

In theory, having 5 valves vs. 2 valves means you have more valve area, so you can run less lift to flow the same. I would think that by running less lift, an obstruction would hurt more than a valve with more lift.

I'll be pulling the head on my 1.8T, and this is my plan:
I'm going to port match the intake ports in the head and manifold, probably to just slightly less than the intake gasket. No polishing will be done.
For the exhaust, I'm going to open the ports as big as I can, and polish it as much as I can.
And now that I've seen your pics, I'll probably check for any obstructions in the bowl area, and run the sides right into the seat, and polish the sides on the exhaust bowls.

For the combustion chambers, I'm going to cc them and make them equal.

Some theorizing:
Enlarging the intake ports will result in a loss of intake velocity at low RPMs, and improve upper RPM breathing. Since these are boosted motors, if you want to flow more at higher RPMs, all you have to do is crank the boost up, so enlarging won't do much, except hurt low-end torque, when you're not on-boost.
For the exhaust ports, in order to get the gases out, you have to rely on scavenging and the piston. With the backpressure from the turbo, there isn't going to be much scavenging, so it's mostly on the piston to do the work. By getting the ports larger, you make it easier to get the gases out.

As for polishing, you want a rough surface anywhere there will be fuel present in the air, so that's the intake ports, intake bowls, and combustion chamber. Rough surfaces promote turbulence to help keep the fuel in the air. Smooth surfaces can cause the fuel to "fall out" and cling to the sides. Not good.
For the exhaust side, polishing helps keep the exhaust temps up by not transferring as much heat into the head, this means you have more exhaust energy transferring into the turbo (should mean quicker spool-up, but it may raise the EGTs) Plus the smoothness helps get the gasses out.

These are the theories I picked up from a couple XR4Ti groups I'm on (and is exactly how I ported my XR4Ti head). There may be some downsides I'm not aware of, so if you know an experienced head porter, you may want to run these by him (or her) If you do, I'd like to know what they say.

BTW, are these both intake shots, or is one an exhaust shot?

4kq

That lip does look like it can and should be cleaned up. But all the caveats hold true: it is a very delicate job, and more than just a hair can mess things up dramatically.

Definitely cc and gasket match. I would really try to find someone locally with a good flowbench if you plan to do *anything* else. The chamber mods will lower compression (+/-).

I agree completely about keeping the roughness.
This is an area that has been well developed in theory and practice. Unless you have 3-d fluid modeling capability or 20 years of experience with that head, forget smoothing the interior of the ports (other than the match to the gasket!). You want to minimize the edge effect.

dangonay

These are not my first heads. They are my first "Audi 5 valve" heads. This is why I'm not doing anything till I've gathered some more specific info regarding these heads.

dangonay

Here's one cylinder just after I took the head off.

<img src="http://pictureposter.audiworld.com/19185/cylheadclose.jpg">

Here's one of the intake ports. Not bad actually.

<img src="http://pictureposter.audiworld.com/19185/intclose.jpg">

Here's an exhaust port. Notice the piece of metal sticking out on the left edge of the right valve? I thought it was some sort of buildup, but it was aluminum. Maybe a casting remnant?

<img src="http://pictureposter.audiworld.com/19185/exhclose.jpg">

Edited:

I still would like to know if I can change the valve guides on this head or not. It looks like they can be, but I'd like another opinion.

MikTip

Alot of "smoothing" could be done on both the intake ports & exhaust ports.

The factory cast are often quite rough.

xr4tic

leave them rough. It won't make a big difference during low RPM conditions (off-boost) and boost will push it's way through without much of a problem. Plus the roughness keeps the fuel in the air.

Unless you have some major obstructions, I'd leave the intake ports alone. I'm only going to gasket match the intake ports and remove any lip that may be in the bowl/seat area.