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#1
11-12-2006, 08:22 PM
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New fuel fittings leaking
I have a problem with my connections seeping gas. I have a plug installed in one of the holes in my sump and it seeps gasoline. It also seeps at my regulator. I have gasoline grade teflon on the treads but they still leak. Any advice? or tips?
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1976 trans am. 400 .040" over stock crank, CAT rods, speedpro flat tops, 72cc eheads, rpm intake, quick fuel 750, xe274, 1.5 HS. Built 700r4 (by me) w/3200 EDGE converter. 3.73's hustler headers. Flowmaster exhaust system. 17" torque thrust II's |
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#2
11-12-2006, 11:49 PM
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I have good luck with the liquid version of teflon tape
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70 GTO 462 E-Heads TKO-600 9-Inch/3.60's |
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#3
11-13-2006, 12:17 AM
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assuming you're asking about NPT fittings, try tightening them up more.
npt's seal on the threads and are tapered; often just a 1/2 turn extra will stop them leaking.
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#4
11-13-2006, 12:46 AM
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pipe thread fittings and AN both do better if when they are new you tighten then loosen and retighten several times to mate the 37º bevels on the ANs and in the case of pipe plugs the tapered threads themselves. NPTs can take a lot of tightening just remember too tight and whatever you are tightening into can split as the taper tries to widen the receiving fitting.
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#5
11-13-2006, 01:38 AM
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good point; i've successfully split several castings this way!
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#6
11-13-2006, 02:09 AM
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My 5-port Mallory regulator is threaded for AN fittings although a 3/8" NPT fitting screws in - it doesn't seal. I don't remember reading anything about the AN requirement either, and since my smaller 2-port Mallory regulator on the street car was NPT, I almost didn't catch it.
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Mick Batson 1967 original owner Tyro Blue/black top 4-speed HO GTO with all the original parts stored safely away -- 1965 Catalina Safari Wagon. |
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#7
11-13-2006, 02:15 AM
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use blue lock-tite on those fittings that seep, fills the voids and seals. never ever use any teflon product. teflon lubricates, it does not seal, it is there to prevent galling.
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#8
11-13-2006, 04:05 AM
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Quote:
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  My Daddy bought me a car but all I got was this old Pontiac.
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#9
11-13-2006, 11:07 AM
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did you buy new fittings or did you have ones that you knew didnt leak. i bought the jegs brand 8an fittings and my leaked also. tookthem to a machinist and he showed me where there was no flair at the top of the threads so even w/sealer it wouldnt seal. straight from top to bottom. of course jegs had never heard of this.new russel fittings problem solved.
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#10
11-13-2006, 11:37 AM
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Make sure that you are not using any teflon tape or any type of sealer on AN flare fittings. Only use teflon tape or sealer on pipe thread connections. I prefer to use a paste teflon type of pipe dope (thread sealer) for a pipe thread and do not recommend teflon tape as it can contaminate your fuel system. If a flare connection is leaking inspect the sealing surface of the male and female side of the sealing surfaces (the flares) and you will probably see a visable defect, like a scratch. A pipe thread is tapared and the threads actually do the sealing. A flared AN fitting seals on the flares and not on the threads.
Tim C
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Tim Corcoran |
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#11
11-13-2006, 12:08 PM
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engineer, that's wrong, sorry.
on a tapered npt fitting, the teflon does seal, and works great, and has for 50 years. tim is correct, never use teflon on an army-navy fitting; the threads are not meant to seal, the flare is. use antisieze or motor oil as a lubricant. lust, your 5 port regulator is meant to use sealing washers or o-rings on those AN holes.
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#12
11-13-2006, 01:15 PM
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The type of thread sealant that I use is available at Home Depot and is made by "Rector Seal". I have used Rector Seal brand thread sealants since the 60's and it is a quality product. I don't remember when they started offering it with teflon. Thread sealant is not pure teflon; it just has teflon added to the formula to prevent galling.
Tim C
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Tim Corcoran |
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#13
11-13-2006, 06:08 PM
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here are some pictures of where most of my leaks are coming from. I am going to go out and retighten them today.
 
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1976 trans am. 400 .040" over stock crank, CAT rods, speedpro flat tops, 72cc eheads, rpm intake, quick fuel 750, xe274, 1.5 HS. Built 700r4 (by me) w/3200 EDGE converter. 3.73's hustler headers. Flowmaster exhaust system. 17" torque thrust II's |
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#14
05-07-2016, 10:28 PM
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Quote:
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#15
05-08-2016, 09:14 AM
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Quote:
NPT fittings use a tapered thread and usually use some form of thread sealer. The two are not designed to work together (male and female threads being different, one AN and the other NPT). Metric threads are also different. Giving it a additional 1/2 turn does not work with incompatible threads. Tom V.
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"Engineers do stuff for reasons" Tom Vaught Despite small distractions, there are those who will go Forward, Learning, Sharing Knowledge, Doing what they can to help others move forward. |
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