Underhood Project
Including all rubber hoses, refinish intake/valvecovers, GTS breather conversion

The project was really all maintenance and no performance work so it is hard to explain the increase in HP and torque. The only slightly performance oriented work was a little intake grinding/polishing. I only did hand work with a die grinder and could not reach the whole length of any of the intake runners. The other work included injector clean and test, new plug wires, new vacuumn hoses throughout, new knock sensors and idle regulator and of course new gaskets/seals for all parts touched. The repaint job on the intake as we all know won't effect horsepower..nudge, nudge...wink, wink.

I have pictures and info on the parts of the job that seem to not be covered anywhere else. For the basics checkout Tony's fabulous site at http://members.rennlist.com/v1uhoh/ and the 928 owners club site http://www.928oc.org/

Here is the new Powder coating without removing the valve cover technique, just spray em, wrap them in tin foil and rev to 6K for about an hour. See they turned out fine!

I thought my bench might be helpful to others, it is self supporting and does not touch the car. It reached over the loooong nose(protruding under rug to the left) to the back edge of the radiator.

It made working in the intake area a lot easier not having to lean over from a standing position. The intake is heavy enough that it is hard to lift or reposition leaning over, but standing on the bench and shock tower was a comfortable position for leverage reasons.

These are the pictures from my GT to GTS crankcase breather conversion. The first 2 show the restricter plug I put into the open hose barb on the oil breather and the cap I covered the valved hose barb with. The restricter plug is bored to 5 mm as speced in the manual for a GTS. The manual comments that the de-icing valve was eliminated on the GTS and I assume this valve is the one they are talking about since there aren't any others obvious in the system and the GTS hose layout shows this connection as eliminated. The parts on the right are all of the components for the new arrangement. The hoses are the correct GT hoses for the valve cover connection with the throttle body side cut off and the big sweeping L saved. The copper tubing is 3/8 inch pipe with 2 45 degree elbows.
Here is the end of the copper tubing on the drivers side protruding from under the intake. There is a clear path straight across at this point for the GTS
plumbing to fit in.
This one is the connections completed on the passenger side. The rear hose fitting into the valve cover has a restriction which I forgot to drill out, and an identical part is used on the drivers side cover which I did remember to drill out. I am not too worried about the restrictions because the restriction in the oil filler pretty much limits overall air flow through the system so these may reduce it a bit more which might be a good thing.
These are some pics of the polish work I did on the intake and throttle body, this was just a long stone on a die grinder and I just reached in as far as possible and called it good. My main goal was to try to make the sides smoother to reduce the oil retention on the walls of the intake, at least down close to the heads where it cooks on as thick as 50 or 75 thousandths.

Here is a little problem that bothered me, the return spring for the throttle valve (the one on the actual throttle shaft, not the nearby lever mechanism) has a distinct wear pattern where it rubs on the neighboring lever mechanism. The picture isn't great, but you can kind of see the wear in the shiny spots, worst at the left side of the picture. I measured the wire diameter at about 39 mils and the wear had reduced the wire to under 34 mils. Not a significant percentage, but a narrow spot in a spring focuses flexure at that spot so.....I don't know. The spring is not available separately of course so you can get a new throttle body at about 1K just like you can get new flappy bearings at about $1200 by getting a new intake. Anyone seen this? or found a replacement spring?