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Right way to install AN fittings on valve cover

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pbwu1f

10+ Year Contributor
222
0
Feb 27, 2009
West Palm Beach, Florida
I read up on some good threads on catch can and decided on what on going to go with. My question is, what's the right way to install AN fittings on a valve cover? I understand you need to drill and then weld, I'm not the best fabricator but I will like to learn. Any tips would be greatly appreciated. Thanks
 
I would use a hole saw a little smaller than the diameter of whatever size aluminum -AN weld bung you choose, drill the valve cover, use a carbide burr to open the hole up to the correct size and have someone tig it in place. Just be sure to stay above the oil baffle or you'll have problems. You may have to remove the baffle to get the transition from the bung to the valve cover on the inside correct and have it welded back in place.

See attached. This is using -8
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A glued in AN fitting? :hmm: That makes zero sense, why would anyone buy that? I don't see how that is easier, cheaper, or an upgrade over stock.

It's just blow by gasses seeing very little pressure and vacuum. I don't understand why people coin up big $$ for AN fittings and lines.
 
Why is it considered less reliable if you drill and tap it and use a screw in AN fitting? That's what I planned on doing for my PCV system as I'll be running dual catch cans. one would think that if the fabricator/owner had a good working knowledge of plumbing that it would be reliable as long as it was done right with the right threads and so on.
 
I have mine drilled and tapped, and screwed in my an fittings. I used some rtv to seal the threads as well. It work's just as good as welding them. Save yourself the extra money on getting a welder to do it (unless you can do it yourself), and just tap it.
 
I'm pretty sure on a 1g you have to come in from the side, because the fittings will hit the hood if you come in the top. Going in the side almost requires welding. There is nothing wrong with drilling and tapping for fittings.

If you want to weld them on, you should take the baffle out of the valve cover and clean the area extremely well, inside and out. It has to be nice clean bare aluminum for several inches from the weld. Then I welded the fittings on, and drilled the holes out afterward.

If you have a fairly high boost setup its probably best to go with some -10's or bigger as there's a lot of blow by gasses on a 30+psi setup. I was blowing my dipstick out on a good motor even with -10's on about 35psi.
 
Top mount runs into hood on a 2g as well, unless u have aftermarket hood.
 
I see nothing wrong with the STM fitting aside from it being just as restrictive of an orfice as the factory one.

I also dont see a good way to drill and tap the VC. There's not much room to thread in a large fitting. And going larger is the whole reason in the first place. Welding on fittings is the best way to go.

mitsubishikid - What size NPT did you thread in?
 
Nothing wrong with the STM fitting, it's a quick solution for people looking to run a catch can with AN fittings rather than nipples.
 
A glued in AN fitting? :hmm: That makes zero sense, why would anyone buy that? I don't see how that is easier, cheaper, or an upgrade over stock.

It's just blow by gasses seeing very little pressure and vacuum. I don't understand why people coin up big $$ for AN fittings and lines.

My thoughts exactly. I can't believe STM would sell such a piece of shit on their website.

My thoughts exactly.

You all have got to be kidding me. Since when was bashing one of our largest vendors OK? Im pretty sure that they wouldnt sell it if it wasnt functional. At ease that shit.
 
Nothing wrong with the STM fitting, it's a quick solution for people looking to run a catch can with AN fittings rather than nipples.

well for $25 [+shiping/handling] you could buy a 1/8 npt tap, and a drill bit, as well as a fitting to thread into it. Im not saying the stm peice is junk, but for the same cost you can get a tool that can be reused a few times, and a working fitting.

[Note: 1/8 npt is nearly the same size as the stock barb fitting on there]
 
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You all have got to be kidding me. Since when was bashing one of our largest vendors OK? Im pretty sure that they wouldnt sell it if it wasnt functional. At ease that shit.
Where was I bashing the vendor? Seriously, try not to be a complete STM nutswinger. Why can't we have an unbiased discussion on parts available in the community without worrying about vendors feelings? I don't get it dude. The product was simply questioned others question its validity as well. You do realize the fitting is contradictive, right? It defeats the point of going -AN. It's also -6, which has to be damn close to the size of the stock nipple on the valve cover. So even if it wasn't glued in, I still don't see why someone would spend the coin on replacing the stock nipple and rubber hose with stainless lines and -AN fittings only to end up with what was already there from the factory. The only reason I can honestly think is if they were doing it for looks and looks only. Let's keep in mind the title of the thread is "Right way to install AN fittings on valve cover" and that product does not fit the bill.
 
You all have got to be kidding me. Since when was bashing one of our largest vendors OK? Im pretty sure that they wouldnt sell it if it wasnt functional. At ease that shit.

You realize just cause they're a large vendor doesn't mean they don't sell shit.

Let's examine the product shall we? They say it's a tight fit but tight fit is about as descriptive as "two of the large ones." They also recommend gluing it. I'm all for JB weld but that's ridiculous. I've never seen any glue that was able to hold up to much torsional forces and I like to crank down on AN fittings for a secure fit. Sometimes the mating surfaces don't contact all the way around.
 
Welding something onto the VC is the best way to do it. But you still have many options. In either event, I would always recommend removing the baffle to make 100% sure it's clean under there. The baffle can and will trap debris and you would never want any of that to come loose and risk it making it's way back into the crankcase. Being that the baffle is steel, not aluminum like the VC, it's not easy to reattach. In my opinion, the best solution out there is to buy one of Kevin's aluminum baffles to weld back in. But if you're crafty enough and can safely figure out how to attach the factory baffle, then you'll be just fine running it.

Onto the fittings. Size is determined by how much crankcase pressure you need to evacuate. Someone running 35+ PSI on a 42R is going to need at least two -10 vents, whereas a guy running 18 PSI on a 16G could easily get away with two -6 vents. It's completely proportional to how much cylinder pressure and blowby you have on your particular setup.

There's many different ways to plumb the valve cover. Plumbing off the top of the VC usually won't clear the underside of the hood unless you either have an aftermarket hood or you're using rather small sized fittings. So, most guys come off the side of the VC. When plumbing to the side, just make sure you're above the baffle.

Here's some suggested combinations:


Weld an NPT bung on the side and use a NPT-AN adapter fitting with it. This is great because it's cheap and easy to change AN sizes down the road if the need arises.
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Weld an AN bung directly to the VC. Some also weld the AN bung to a small piece of tube, which welds to the VC. Using a small piece of tube can sometimes make the job easier, and it also helps clearance the bung away from the VC.
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If you have better than factory hood clearance and you want to go off the top of the VC, then you have options there as well. The cheapest and easiest method is to use a 90* AN adapter and weld it right in. Buy an unanodized fitting though, as you cannot weld an anodized one and removing anodizing sometimes sucks (especially when you can order them without it).

Weld this on the top and cut off any excess NPT threads that protrude into the VC. EXAMPLE

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Another option is to use a bung and fitting combination on the top of the VC. I would recommend an ORB (o-ring boss) combination over NPT though, because you can't clock NPT 90* stuff like you can ORB stuff. This combination requires the most hood clearance of all.

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this is what I did to my cover since it was powder coated already.
drilled out the baffles
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tapped and plugged the oem pvc and breather
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used a step drill to make the 10an fitting holes
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used 10an 90 bulk head fittings with jam nuts on the bottom. I used epoxi from work for aircraft jet engines that will never let go in super cold or heat
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it all clears just fine on the evo 3 since the whole center of the hood is higher than the sides
 
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