Fuel line torque values

2560 Views 12 Replies 0 Participants Last post by Henryk (Henryk), Apr 18, 2004

Discussion Starter · Apr 16, 2004

I am putting my FI system back

I am putting my FI system back together, on the Boxer. I will be replacing the copper gaskets where I took the fittings off the WURs.

Can someone tell me the proper torque values for these banjo fuel fittings. I don't want to make a mistake here!

Thanks.

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Discussion Starter · #2 · Apr 17, 2004

Hi Hank...I know that when I d

Hi Hank...I know that when I did my TR I simply tightened the bolts until the leaks stopped. Not the best way - I know. I was surprised at how much I had to reef on the bolts to get the leaks to stop. I was afraid of stripping out the fuel distributor heads.....but things turned out okay. I too would like to know the torque values for future reference.

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Discussion Starter · #3 · Apr 17, 2004

Jeff: My TR manual calls for

Jeff: My TR manual calls for 20 ft/lbs. A normal nut (13mm) going on an 8mm stud is usually torqued down to about 18 ft/lbs. The heads on the FI system are 14mm heads, but, they are going on a 10mm stud......with holes. A normal 10mm bolt (head size larger) would be torqued to about 40 ft/lbs. So I think the 20 ft/lbs sounds about right.

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Discussion Starter · #4 · Apr 17, 2004

Jeff: I just tightened down t

Jeff: I just tightened down the banjo bolts. It would appear that the 20 ft/lbs is wrong!!!!!!!!!!!!!!!!!!

I first went over the bolts on the FD......I did not take these off. When I got to about 10-11 lbs, most of them produced a "sound", and the torque dropped a couple of lbs. I went to 12 ft/lbs and stopped. On the removed bolts, I went to about 10-11 ft/lbs......heard the "crunch", and proceeded to 12 ft/lbs.

While the FDs did not leak before, it was interesting to note that the torques ranged from about 8ft/lbs to 12 ft/lbs. I think I did right, by tightening them all to 12 ft/lbs.

I will now turn on the FPs, and check for leaks.

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Discussion Starter · #5 · Apr 17, 2004

you sure the specs are in Ft L

you sure the specs are in Ft Lbs and not In Lbs?

Porsche 911 Cylinder Heads Torque to 28 Ft Lbs.

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Discussion Starter · #6 · Apr 17, 2004

FWIW:
I just ran the FPs. Sa

FWIW:
I just ran the FPs. Saw some fuel seeping from the double banjo fitting on the WUR. I wiped the fuel and tightened the fitting more.....at 17 ft/lbs, I heard and felt another "crunch". I did finally go to 20 ft/lbs. This fitting has 3 copper washers. I feel the "crunch" is compression of the washer. There where 2 crunches.....one at 11 ft/lbs, and the other at 17.

In the future, I will consider the 12 ft/lbs on those fittings with only 2 copper washers, and 20 ft/lbs on those with 3.

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Discussion Starter · #7 · Apr 18, 2004

JRV: Would you kindly share h

JRV: Would you kindly share how you tighten these down, with us? I tend to agree with you that 20 ft/lbs is a lot. I removed the fittings, and measured the thickness of the "crunched" washers......they where 0.91mm vs 1.0mm new.

I recall the guy at the washer supply house, told me that copper gaskets usually compress only about 37 microns. If so, then the "crunch" I hear and feel, means that I have gone too far???????????

Your thoughts?

Thanks

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Discussion Starter · #8 · Apr 18, 2004

Hi Henry,

well the problem

Hi Henry,

well the problem with trying to describe certian things is that they require "feel"...unfortunately the only real way to show feel is in person.

Reading this I was not so concerned about how much the copper compressed as I was the chance of snapping off a fitting. Actual Torgue with a Torque Wrench & Specific Settings is risky business on small or hollow bolts and on soft metal like APR & FD's. To my mind the greater chance of a leak would come from a cracked or stripped fitting than from a fitting being to loose. You can always tighten a little greater by hand in case of a weep, but you can't unbreak or unstretch a bolt that has been overtightened.

I think a good example may be Brake Line Fittings...they are not Torqued in the actual sense but tightened until they have no chance of ever loosening on their own and they don't leak...and I think that would suffice for an explanation of how tight fuel lines should be.

HTH's

Regards, JRV

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Discussion Starter · #9 · Apr 18, 2004

JRV: Thanks for your help.

JRV: Thanks for your help.

I understand about some things that have to be done by "feel", thus cannot be adequately described in words.

The compression figures I gave are wrong.....it seems that the Ferrari gaskets are 1.0mm, while the ones I bought are slightly thinner. I used the thinner ones, to start with, thinking that they where 1.0mm also.

My concern for some "definitive" torque value shows my paranoid feeling of some disastrous fuel leak.......read, engine fire!!!!!!!! I have read that tightening them down TOO much is no good.

I have also learned that one should NEVER re-use the gaskets. I am glad I bought them by the hundreds..........better order a few hundred more......haha.

Have you ever seen a "weep" that was tightened slightly, to where the leak went away, and then later, saw it leak again.......due to engine vibration, and changes in hot and cold engine temperatures?

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Discussion Starter · #10 · Apr 18, 2004

Well, if you have a weep then

Well, if you have a weep then the gaskit has not completely deformed enough to make a leak proof seal...further tightening could finish the job of sealing...by giving additional deformation or crush...if crush is the reason for the weep.

As far as coming loose to vibration or thermal expansion/contraction goes...once the fastener is correctly & sufficiently tight...nothing will cause it to loosen until a wrench is placed on it again.

Am I making any sense?

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Discussion Starter · #11 · Apr 18, 2004

Yes you are........thanks.

Yes you are........thanks.

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Discussion Starter · #12 · Apr 18, 2004

Hello JRV and Hank....I guess

Hello JRV and Hank....I guess my actual results show that what JRV says is true. I tightened down the bolts to what I though was "sufficient" but after starting the engine leaks were found. I then tightened them further, two steps in all...just a bit at a time, until the leaks stopped. I too was concerned about hollow bolts and the aluminum fuel distributor top, how much would I have to go? I didn't use a torque wrench when I tightened them down so I can't give you an actual number. But going by "feel" it was tighter than I was comfortable with. But thank goodness it all worked out fine as 4k miles of driving showed no more leaks. There are some variables at work here, as the banjo bolts are quite long, and the longer they are the more force they can apply to the copper washers. The thicker the copper washers are, the more vertical crush they are able to withstand, as their rate of compression is based on the amount of material available - thickness-wise. There must be an actual spec. for tightening these down. But since this magical number seems to be in question, you can do what I did and just tighten them by trial and error. You just have to be careful I guess. The results I observed corroberate what JRV says, once tightened sufficiently everything should be fine. But just what is "sufficient" is the big mystery. After tightening several times I did not have any fuel leaks down the road. I do share your concerns as the importance and safety of this procedure cannot be over-stressed.

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Discussion Starter · #13 · Apr 18, 2004

Just got through re-installing

Just got through re-installing the fuel lines to the WUR, after doing fuel pressure tests. I snugged them up to start, then let the fuel pumps run.......wiped up seepage, turn slightly more, etc., till leaks where gone. No where near 20 ft/lbs. I did check the torque, and it was something like 11-12 ft/lbs on the double banjo fitting, and slightly less on the single banjo fitting (the double fitting is a 10mm hollow bolt, while the single fitting is only an 8mm hollow bolt). I did not have to go to the "crunch" level.

I am now re-installing the top halves of the intakes........there are a LOT of vacuum lines!!!

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