April 11, 2012

Vacuum Routing

I think I've developed an obsession with these push-to-connect fittings. I created a decent amount of trouble for myself to run them on both the ends of my vacuum lines.

The vacuum block doesn't really need any further explanation, but I'll elaborate on the vacuum fittings. Sourcing push-to-connect style fittings for the five 1/8" NPT ports and 1/4" NPT ports was the easy part. Conjuring up matching fittings for the areas that have no threads was a bit trickier. I was already confronted with this situation when adapting to my vacuum source off of the intake manifold. My solution was a sort of adapter using push-to-connect fitting with a tube stem, instead of threads, in the correct diameter to fit in an old PCV elbow. After a lot of brainstorming I settled on a similar approach for the nipples on the stock FPR and HKS BOV. However, since the stems were designed to work with their outside diameter and I needed the inside diameter, these two areas required a bit more imagination.

The nipples I had to work with measured roughly 3/16" in diameter (just shy of 5 mm) and, after much hunting, I couldn't find either a push-to-connect coupler or barb that would fit (while still accept the 4 mm vacuum line). I eventually took a gamble on some fittings with a 3/8" stem for the 4 mm hose, mistakingly assuming that the ID would be 4 mm straight through (in which case I could drill out the ID for a press fit). Unfortunately this proved to not be the case. I then contemplated making up some nylon inserts to give me that appropriate inner diameter but then, while sifting through the local hardware store, I found something even better - rubber expansion nuts with a 3/16 ID. They did have a threaded brass insert, but after drilling those out I was left with a piece that fit snugly both inside the stem and over the nipples. Before final assembly I used a pipe cutter to trim some excess length off and voila, my own custom fittings.

On the simpler side of things I did have to remove one of my 4 mm fittings for a 1/8" fitting. For whatever reason I had assumed the diameter of the supplied Auto Meter vacuum hose (for the boost gauge), only to discover that my assumption was wrong.

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