TR Paul Posted June 24, 2017 Report Share Posted June 24, 2017 Good evening, fellow TR6ers... as some of you might recall, this time last week I was asking for your excellent advice regarding 'weeping banjos' on my TR6 metering unit. Today, I have tackled that problem (seemingly successfully, so far...), & fitted new 'o' rings to the aforementioned banjo bolts. However in the process of re-bleeding the injectors, I've found that the thread (for the bolt that holds the injector retaining plate) in the injector 1&2 manifold has stripped. I had recut this thread (5/16'' unf) last year, as a p.o. must have had similar problems, & he (or she) had wound in a fairly nasty metric bolt. I have made a temporary repair by winding some tape made by 'Scotch' as a kind of thread lock 'round the offending bolt, but I am looking for a more permanent soloution (without having to have my manifolds re-conditioned, or even removed from the car, if possible..). Perhaps using chemical metal, or something similar,& re-cutting the thread into that, Or just opening the hole out & cutting a bigger thread (for a bigger bolt!)? Any ideas? Your advice, as always, is much appreciated, Cheers, Paul. Quote Link to post Share on other sites
RogerH Posted June 24, 2017 Report Share Posted June 24, 2017 Hi Paul, the easiest and best fix is a HeliCoil. https://www.ebay.co.uk/sch/i.html?_odkw=bondarust&_osacat=0&_from=R40&_trksid=m570.l1313&_nkw=5%2F16UNF+helicoil&_sacat=0 Very easy to use Roger Quote Link to post Share on other sites
john.r.davies Posted June 24, 2017 Report Share Posted June 24, 2017 Had this myself. A longer bolt does the trick! But its UNC, not UNF! John Quote Link to post Share on other sites
88V8 Posted June 24, 2017 Report Share Posted June 24, 2017 Bolts don't need to be tight. Even without the keep plates, injectors won't fall out. Ivor Quote Link to post Share on other sites
Peter Cobbold Posted June 24, 2017 Report Share Posted June 24, 2017 (edited) Glue in a stud - epoxy. Edited June 24, 2017 by Peter Cobbold Quote Link to post Share on other sites
Waldi Posted June 25, 2017 Report Share Posted June 25, 2017 Like John says: UNC. This is also a much more suitable thread for the soft alloy. Waldi Quote Link to post Share on other sites
barkerwilliams Posted June 25, 2017 Report Share Posted June 25, 2017 Paul, There seem to be two types of casting on the injector retaining plate bolt holes, an open hole where the bolt can protrude out of the bottom and a closed off hole. If a slightly longer bolt is used on a closed hole the bolt bottoms out and either pops the casting or strips the thread. If the "bling" stainless retaining plates are used, these are thinner and the original bolt penetrates lower into the threaded hole and can bottom out before the plate is "tight" and leads to over-torquing.. If you need to do work on the castings it may be better to ensure the fixing hole is drilled through to allow for the accidental fitting of a longer bolt. The injectors are fitted in the pi inlet manifold not the combustion chamber as are so many modern systems and the retaining plates only need to stop the injector either vibrating out or being pushed out with a backfire and need only to be finger tight'ish. Alan Quote Link to post Share on other sites
TR Paul Posted June 25, 2017 Author Report Share Posted June 25, 2017 (edited) Thanks chaps,sounds like good advice. My manifolds are the ones with the open hole ( and I was using a longer bolt; D'oh!!!). I cut fine threads, as the parts lists from Rimmers & Moss say 5/16'' unf..... Cheers, Paul. Edited June 25, 2017 by TR Paul Quote Link to post Share on other sites
RogerH Posted June 25, 2017 Report Share Posted June 25, 2017 Hi Paul, the Moss webcat shows the retaining screw as UNC item #28 http://www.moss-europe.co.uk/shop-by-model/triumph/tr5-6/fuel-system-induction-controls/fuel-injection/injection-system.html 5/16 UNC helicoil is still the best repair - honest. Roger Quote Link to post Share on other sites
john.r.davies Posted June 25, 2017 Report Share Posted June 25, 2017 Quote, "the parts lists from Rimmers & Moss say 5/16'' unf....." Can't trust anyone these days. New thread will do the trick, but it must be a bigger bolt, else the 'new' thread will only be where it doesn't cross the old, and will soon fail again.. 8mm is a little bit bigger than 5/16, 3/8 a lot bigger. Peter, you crossed out your glued-in stud idea. What's wrong, apart from the cries of consternation and dropped knitting from the originality brigade? You might have to slide the retaining plate onto the stud with the injectors as they go in, fiddly but not done often. John Quote Link to post Share on other sites
Peter Cobbold Posted June 25, 2017 Report Share Posted June 25, 2017 Quote, "the parts lists from Rimmers & Moss say 5/16'' unf....." Can't trust anyone these days. New thread will do the trick, but it must be a bigger bolt, else the 'new' thread will only be where it doesn't cross the old, and will soon fail again.. 8mm is a little bit bigger than 5/16, 3/8 a lot bigger. Peter, you crossed out your glued-in stud idea. What's wrong, apart from the cries of consternation and dropped knitting from the originality brigade? You might have to slide the retaining plate onto the stud with the injectors as they go in, fiddly but not done often. John The plate has to slide sideway to free the injectors. As you say,with a stud all three would have to be lifted, or refitted, together. Peter Quote Link to post Share on other sites
TR Paul Posted June 25, 2017 Author Report Share Posted June 25, 2017 Hi Peter/John, I must say I liked the stud idea, 'til you pointed out the shortcomings; helicoil sounds like the best answer to the problem. Cheers, Paul. Quote Link to post Share on other sites
DaveN Posted June 25, 2017 Report Share Posted June 25, 2017 You can use studs but the retainers would need modification to allow them to pivot. The standard bolt is UNC. Removing the washer sometimes allows the bolt to grip the last of the good thread at the bottom, not ideal but will last. Quote Link to post Share on other sites
Peter Cobbold Posted June 25, 2017 Report Share Posted June 25, 2017 Hi Peter/John, I must say I liked the stud idea, 'til you pointed out the shortcomings; helicoil sounds like the best answer to the problem. Cheers, Paul. Paul, Try gluing in a rivnut ? Peter Quote Link to post Share on other sites
astontr6 Posted June 26, 2017 Report Share Posted June 26, 2017 Normal engineering practice is course threads for ali and cast iron as I was taught when I was an engineering apprentice in the 1960's and have always followed this practice. As others have said use UNC only. Bruce. Quote Link to post Share on other sites
Chilp3 Posted June 26, 2017 Report Share Posted June 26, 2017 Hi Paul, To add to the discussion I had the same issue with one of my CR manifolds. A local machine shop put a heli-coil in and it has been perfect ever since and visually you would never know. Best Regards, Peter Quote Link to post Share on other sites
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