Catch can fittings for valve cover

[turboglenn]

I would recomend using 3/8NPT to -8 (or -10) fittings, that way you drill and tap instead of welding adn can keep your powder-coat, and you will have enough air flow tomake them worth while. Although it may not look the best i have seen it done, the only isse being that with the baffles in place you can't runthe tap, or thread the fittings in very far, but it still looks very respectableand a lot better than JB weld (no offense to those who use it on theirs)

But even with -10 to 3/8NPT fittings barely threaded in you'll gain a lot of venting flow for the crank case. And to be honest once they are in and you've accepted the threading rather than welding they won't look out of place at all, probably no one will even ask "why didn't you weld them" because they end up looing just fine other than the fact that if you get it going in crooked it will look funny. Another thing i can give a hint for on this is only thread them in ONCE and don't over tightenthem, just go snug enough to know they'll stay (and you can use some JB or Red loc-tite) I say this becayse my buddy cracked 2 valve covers doing his thread in ones thinking they needed to be air-tight at the threads (Which they don't) plus if you thread them in and out you beat up the fitting and since you're not "re-coating" them after the install you'll want them to look as good as possible without scratching off the anodizing.

Anyway, I don't think you'll be dissapointed at all with the results after trying it. And with you're PC'd VC the mating joint probably won't stick out nearly as much as a big blue fitting does on a polished VC.

Try it out and post up some pics

 

[jpmxrider489]

Are you saying not to drill all the way through? I can drill all the way then tap it then thread it in till it's tight. The way the guy above made it sound like its impossible to do but you guys make it sound that's it's easy and good thing to do. Calan, you make it sound like 1/2 us possible. So if the 1/2 is like 10an, would 3/8 or 1/4 be like 8an?

 

[romeen]

Are you saying not to drill all the way through? I can drill all the way then tap it then thread it in till it's tight. The way the guy above made it sound like its impossible to do but you guys make it sound that's it's easy and good thing to do. Calan, you make it sound like 1/2 us possible. So if the 1/2 is like 10an, would 3/8 or 1/4 be like 8an?

Actually I'm saying the exact opposite of this (see quote below ). I put the pics up to show that it IS POSSIBLE. But if you have spent money to get it powder coated it might not be worth the risk of cracking it.

To reiterate, I'm not recommending this but rather just saying that it can be done.

The reason for not going too far in with the tap is that NPT threads are tapered. The diameter of the tap gets larger going from the tip back. So the farther you run the tap the higher the possibility of causing a crack.

This is a breather hole that has had a 1/4 NPT tap run through it. If you look closely you can see a crack at the top of the hole. If I screw in a fitting the crack starts to spread and widen the farther I screw it in.

 

[jpmxrider489]

So would 1/4 be close to 8an?

 

[Gamble97]

So would 1/4 be close to 8an?

a -2 hose has an I.D. of 1/8" [306 only]
a -3 hose has an I.D. of 3/16"
a -4 hose has an I.D. of 1/4"
a -5 hose has an I.D. of 5/16"
a -6 hose has an I.D. of 3/8"
a -8 hose has an I.D. of 1/2"
a -10 hose has an I.D. of 5/8"
a -12 hose has an I.D. of 3/4"
a -16 hose has an I.D. of 1"
a -20 hose has an I.D. of 1 1/4"

 

[99gst_racer]

So would 1/4 be close to 8an?

1/4 NPT is a better match to -6 AN. And 3/8 NPT to -8 AN.

 

[jpmxrider489]

I just ordered the fittings. I'm going to drill for the 1/4 and if I feel that 3/8 will be ok them I'll do that. Thanks for all the help and I'll post pics of it later.

 

[phizzalot]

There is great information in here. I think I will try the -10an route and hit it with some AlumiWeld / Torch to seal it up.. I would think that would hold.

 

[turboglenn]

Are you saying not to drill all the way through? I can drill all the way then tap it then thread it in till it's tight. The way the guy above made it sound like its impossible to do but you guys make it sound that's it's easy and good thing to do. Calan, you make it sound like 1/2 us possible. So if the 1/2 is like 10an, would 3/8 or 1/4 be like 8an?

NO, i'm saying to watch your depth so you don't hit and or damage the baffles inside, with either the dill bit, taps or by threading the fitting in too far.

 

[Calan]

a -2 hose has an I.D. of 1/8" [306 only]
a -3 hose has an I.D. of 3/16"
a -4 hose has an I.D. of 1/4"
a -5 hose has an I.D. of 5/16"
a -6 hose has an I.D. of 3/8"
a -8 hose has an I.D. of 1/2"
a -10 hose has an I.D. of 5/8"
a -12 hose has an I.D. of 3/4"
a -16 hose has an I.D. of 1"
a -20 hose has an I.D. of 1 1/4"

You are about 1/8" too big on those numbers, as far as realistic sizes for figuring flow through the line. Regardless of the hose ID (which varies a lot), the fittings and weld bungs that the lines connect to will be the choke points, and should be used for calculating cross-sectional area for flow.

Most -8AN weld bungs will have an ID of close to 3/8", most -10AN fittings around 1/2", -12AN around 5/8", etc.

 

[jpmxrider489]

You are about 1/8" too big on those numbers, as far as realistic sizes for figuring flow through the line. Regardless of the hose ID (which varies a lot), the fittings and weld bungs that the lines connect to will be the choke points, and should be used for calculating cross-sectional area for flow.

Most -8AN weld bungs will have an ID of close to 3/8", most -10AN fittings around 1/2", -12AN around 5/8", etc.

So to your calculations 3/8 would be about the same as 8an.

 

[Calan]

So to your calculations 3/8 would be about the same as 8an.

Yep...just like Paul said a couple of posts earlier.

1/4 NPT is a better match to -6 AN. And 3/8 NPT to -8 AN.

 

[romeen]

I found some notes I jotted down back when I installed the larger fittings. The i.d. of the stock fitting was .25". The new fittings are .37" i.d. On paper it doesn't seem like much but if comparing the fittings side by side the difference is quite obvious.

 

[jpmxrider489]

Ill have to post pics when im done. Thanks for all the help.

 

[Calan]

I found some notes I jotted down back when I installed the larger fittings. The i.d. of the stock fitting was .25". The new fittings are .37" i.d. On paper it doesn't seem like much but if comparing the fittings side by side the difference is quite obvious.

Yep... a fitting with .37" ID has about 219% more cross-sectional area than one with an ID of .25". That equates to a considerable increase in flow.

 

[romeen]

Yep... a fitting with .37" ID has about 219% more cross-sectional area than one with an ID of .25". That equates to a considerable increase in flow.

Wow, that's a lot more than I thought it would be. Glad to know that! Thanks for doing the math Craig.

For anyone considering using the NPT fittings, look for ones that have a constant i.d. all the way through. I found that some have a neck down through the threaded portion.

 

[Calan]

Wow, that's a lot more than I thought it would be. Glad to know that! Thanks for doing the math Craig.

NP. It's good to dust off the 8th grade math every now and then.

It's surprising how much flow increases with small changes in ID (until you remember the power of squares). For future reference, here is how you can calculate the difference in cross sectional area between two different inside diameter openings:

original area = Pi * radius(1) * radius(1)
new area = Pi * radius(2) * radius(2)
percent difference = new area / original area

So for Romeen's example:

original area = 3.141 * .125 * .125 = .0491
new area = 3.141 * .185 * .185 = .1075
percent difference = .1075 / .0491 = 2.189, or 219%

In his case, that extra .12" of inside diameter added .058" of cross-sectional area... more than the original .25" ID had to begin with.

A handy rule to remember is that doubling the ID of a pipe gives 4x the cross-sectional area and flow.

 

[romeen]

I found some notes I jotted down back when I installed the larger fittings. The i.d. of the stock fitting was .25". The new fittings are .37" i.d. On paper it doesn't seem like much but if comparing the fittings side by side the difference is quite obvious.

One thing I forgot to mention. I ran a 3/8" drill bit through all the fittings to increase the i.d. to .37". So I guess you could say that I'm using 1/4 NPT fittings that have the internal flow area of a 3/8 NPT (-8AN) fitting. The fittings I'm using are particularly beefy (local find ) so they still have plenty of meat left in the wall. I even drilled out the EVAP nipple on my Injen intake pipe to .37" to connect the breather to.

Brief off topic FYI Craig. You can hold down the "Alt" key and type 253 to get the squared sign--> radius²

 

[Calan]

Brief off topic FYI Craig. You can hold down the "Alt" key and type 253 to get the squared sign--> radius²

Cool... but I bet a lot of our current members wouldn't understand what "squared" means.