my944

I need the thread size of the metric cap nut on the end of the fuel rail on my 86na...I am looking for an adapter to go from metric to standard and even the local P dealer does not have the exact size (so they say)

Best regards...

instigator

12mm x1.5 i'm looking for one too if you come accross them please let me/us know thanks

my944

Instigator,

You mean the ID of the threads on fuel rail is 12mm? It's that large? If I get this all figured out, I'll send you my cap for free.

marksportcts

Are you trying to put a fuel pressure gauge? 9xauto.com has the adapter block and the gauge.

my944

I will not comment on 9xAuto ("if ya got nothing good to say...")

instigator

my944 if i recall correctly its is a 12mm i will look in my manual tonight to see, by the way its in the manual if you have a cd copy of them or hard copy. its on the pages where all of the nuts and bolts threads sizes are.

thanks for the cap but i want the adapter i want to put my gauge in the middle of the intake manifold (between #2-3 runners) so i'm in need of a 90 degree elbow and a length of braided line to achieve this. good luck in finding the adapter(not said sarcasticaly)

instigator

yep its 12mmx1.5

i was looking at the other fuel rail that i have and the boss thats at the end for the test port is really thick and i was thinking of lopping of the threaded portion, drilling and tapping the boss for the 1/8 pipe for the gauge, this will set the gauge back about 3/4in enough that you wont have to worry about it hitting the hood, the only down side of it is youhave to remove the rail to do it right (cleaning the debris out after)i'm really entertaining that idea.

keith

you guys are really making this harder on yourselves than you have to - just drill and tap the factory cap to accept whatever pipe/hose/fitting you need!

New caps are in the $5 range, anyway.

instigator

Keith i'll give you a couple of reasons why the cap method isnt all that, 1 the sealing feature of that cap is the ball inside, once its out the seal now becomes the end of the threaded nipple or the threades themselves. 2 it really doesnt have enough meat on the cap when you drill and tap it, then that becomes a weak spot. 3 it protrudes too much foreward being a good chance to ding the hood and displacing the gauge inside the weak threads. 4 every body has it there

Skip

[quote]Originally posted by instigator:
<strong> 2 it really doesnt have enough meat on the cap when you drill and tap it, then that becomes a weak spot. </strong><hr></blockquote>

Good point, and I thought the same thing until the first time I did it. The real problem is the aluminum is far too soft to provide a real secure fit. The depth of the material and thread engagement was perfectly acceptable... but turn the gauge too vigorously and you'll strip the cap. There's no cure to losing the ball from the cap unless you tap the rail directly.. and there's no real good place to do that... nor is it as easy to clean after such surgery. Even the remote senders are tapped into the cap. The real answer is to get a custom fitting... as discussed in the other recent thread on this subject... but they aren't free - this is Ultimately I'd like to see someone develop an affordable billet rail like all the popular imports have available to them. Then it could easily be developed with a purposeful fitting for the specific purpose of running a rail-mounted or remote pressure gauge.

The gauge *should_not* touch the hood when closed... it's REAL close... and you may have to remove some of the hood padding, if equipped.

Skip

keith

[quote] 1 the sealing feature of that cap is the ball inside, once its out the seal now becomes the end of the threaded nipple or the threades themselves. 2 it really doesnt have enough meat on the cap when you drill and tap it, then that becomes a weak spot. 3 it protrudes too much foreward being a good chance to ding the hood and displacing the gauge inside the weak threads. 4 every body has it there <hr></blockquote>


Hmm, doesn't #4 suggest that 1-3 might not be correct?

BTW, haven't had any leakage problems with mine, hood clears (but I drilled at a slight angle - the condition/height of your motor mounts may make the difference here), plenty o' meat.

The ONLY problem I've had is with heat, which MELTED the PLASTIC lens on my gauge. Don't get the $20 Summit racing liquid-filled SS gauge - I warned you.

If you are attaching a fitting to go to a remote gauge, drilling/tapping the cap is a fine idea. If you are WORRIED about leakage without the ball, use some thread tape or pipe dope or something.

Just trying to save you guys some money...

<img src="graemlins/r.gif" border="0" alt="[king]" />

Julian Allen

You can also take out the rail, buy an AN steel fitting, blast off the cadmium plating and braze the fitting onto the end of the rail after cutting off the original fitting. Then you can use a 180 fitting to bring the fuel pressure line where you want it. Powder coat the rail after you braze it up.

nh3

Try <a href="http://www.mcmastercarr.com" target="_blank">www.mcmastercarr.com</a>

instigator

nooooo 4 only means that every body has them there and thats the simplist way of attaching it(although i like to keep thing simple, but i also like to keep them safe and secure)and not saying that everybody is unsafe i just like to be a little more than the next guy. (aircraft maintenance does this to ya)

if youve got 1/8 clearance but 1/4 is achievable then i might do the 1/4 cause i like the margin

Skip

Julian: I almost did that very thing, but took the easy road for simplicity. The real reason I want rid of the rail is the number of failures reported over the years while I've been lurking the various groups. There are a couple of predicatable weak areas in the rail itself... enough that I didn't want to expend much energy with the pressure gauge.

Instigator: You can't get much of an angle on the cap. Just enough to make a difference though... but then you must worry about orientation once the cap is torqued. The size of the gauge and the ID of the cap are too close to drill at much more than a 2-3 degree angle... if that. Also, because the NPT tap is tapered, there must be quite a bit of clearance for running the tap through enough to get a good seat for the gauge. [it really is easier than I make it sound ]

I've never heard of a failure or engine fire caused by the installation of a rail mounted gauge. Anyone else? I'm truly curious.

Skip