LS1 Throttle Body - PCV Fresh Air Conversion to AN Fitting
Thread Starter
Joined: Mar 2004
Posts: 10,316
Likes: 6
From: Dayton, OH
LS1 Throttle Body - PCV Fresh Air Conversion to AN Fitting Disclaimer: most will likely not care about this mod since it is strictly for appearance rather than function. I'm just sharing this info in case someone was wondering if it was possible.
The stock LS1 throttle body has a 90* piece of tubing with a beaded end that accepts standard 3/8" I.D. rubber hose. It serves as the source of filtered fresh air for the PCV system, and the line goes from the throttle body to the passenger side valve cover. Usually the only time you ever end up dealing with this line is when you need to remove either the valve cover or the throttle body - most likely don't even notice it's there, and fewer probably care.
I have a lot of stainless braided line in the engine bay for my fuel lines, and was always curious to see if this fresh air line could be converted as well. Out came the Dremel, and off came the 90* tube:
The plan was to drill and tap the hole for 1/8" NPT - the tap requires a "Q" size (0.332") drill bit, so I knew it would be close. Unfortunately, I only had 21/64" (0.328") and 11/32" (0.344") bits to choose from, so I started with the smaller of the two. It wasn't big enough to start the tap, so I grabbed the larger bit. In the process of trying to enlarge the hole, the bit snagged on the piece of pipe that was still in the throttle body and pulled it out (that's the small piece on the right of the picture above). Luckily for me, the hole was still small enough that I could tap it for 1/8" NPT since pipe threads are tapered - the tap started cutting about half way up and went from there, leaving this:
Since the hole is a little on the larger side, the fitting screws in pretty far, which is exactly what I was after (I hate when you can see excess pipe threads sticking out). The fitting is a 90* 1/8" NPT to -6AN adapter, giving me this:
Like I said, there really isn't a purpose for this outside of looking pretty, but if you have a lot of braided lines and want to make this one too without using those cheesy fake AN-looking hose clamps, here ya go.
Note: I have aftermarket valve covers that are already tapped for 1/4" NPT fittings for the PCV system, so that end of the equation was already covered in my application.
The stock LS1 throttle body has a 90* piece of tubing with a beaded end that accepts standard 3/8" I.D. rubber hose. It serves as the source of filtered fresh air for the PCV system, and the line goes from the throttle body to the passenger side valve cover. Usually the only time you ever end up dealing with this line is when you need to remove either the valve cover or the throttle body - most likely don't even notice it's there, and fewer probably care.
I have a lot of stainless braided line in the engine bay for my fuel lines, and was always curious to see if this fresh air line could be converted as well. Out came the Dremel, and off came the 90* tube:
The plan was to drill and tap the hole for 1/8" NPT - the tap requires a "Q" size (0.332") drill bit, so I knew it would be close. Unfortunately, I only had 21/64" (0.328") and 11/32" (0.344") bits to choose from, so I started with the smaller of the two. It wasn't big enough to start the tap, so I grabbed the larger bit. In the process of trying to enlarge the hole, the bit snagged on the piece of pipe that was still in the throttle body and pulled it out (that's the small piece on the right of the picture above). Luckily for me, the hole was still small enough that I could tap it for 1/8" NPT since pipe threads are tapered - the tap started cutting about half way up and went from there, leaving this:
Since the hole is a little on the larger side, the fitting screws in pretty far, which is exactly what I was after (I hate when you can see excess pipe threads sticking out). The fitting is a 90* 1/8" NPT to -6AN adapter, giving me this:
Like I said, there really isn't a purpose for this outside of looking pretty, but if you have a lot of braided lines and want to make this one too without using those cheesy fake AN-looking hose clamps, here ya go.
Note: I have aftermarket valve covers that are already tapped for 1/4" NPT fittings for the PCV system, so that end of the equation was already covered in my application.
Thread Starter
Joined: Mar 2004
Posts: 10,316
Likes: 6
From: Dayton, OH
The throttle body is powdercoated - candy apple red if I remember right. It was done back in the 2004-2005 time frame, so it's been that way for a while. Actually matches my FAST fuel rails pretty closely.
