jimt Posted April 29 Report Share Posted April 29 I’m Looking to put a block drain tap on my recently acquired post CP50000 ‘72 TR6. Moss supply 2 different types - the tap type which I would prefer to put on as easier to attach a drain tube/hose too (detailed as TR5, TR6 to CP50000)- and the ‘butterfly’ type like the radiator drain tap (detailed as TR6 from CP50001) Does anyone know if the threads in the block pre & post CP50000 are the same - I think the early cars are 1/2” UNF ? it would have thought they would machine the blocks the same - but if so why the different types of drain tap? Thanks- jimt Quote Link to post Share on other sites
Nigel Triumph Posted April 29 Report Share Posted April 29 The latter type of tap was probably a cost saving measure. AFAIK, the threads are the same. Nigel Quote Link to post Share on other sites
jimt Posted April 29 Author Report Share Posted April 29 Thanks- ironically the later type is now more costly Quote Link to post Share on other sites
BlueTR3A-5EKT Posted April 29 Report Share Posted April 29 (edited) Yes 1/2” unf Buy a short stainless steel head head screw and fit that with a sealing washer. Wrap a plastic bag round the starter motor when you drain the block via the plug to stop the electrics getting soaked. The A2 stainless screws I sourced are 1/2" unf 3/4" long thread - and they are too long. I did think I would put a pile of washers under the screw head but decided that was a bodge too far, as in the future if I forgot to refit the washers I'd be in the effluent. I have reduced them on the lathe to 7/16" thread length. Without the sealing washer they screw in by finger force to full depth in my cylinder block, which has had the thread cleaned up. I use a copper crush washer under the head. What I bought https://www.kayfast.co.uk/view-product/UNF-Hexagon-Set-Screws-A2-Stainless-Steel Experience tells us the modern repro brass drain taps do not always seal from new and need to be stripped and lapped to form a proper seal between the moving part and the screw in bit. They also mix up the threads and it is not uncommon for a BSP threaded tap to be supplied when a UNF item is required. Radiators tend to be BSP threaded. Edited April 29 by BlueTR3A-5EKT Quote Link to post Share on other sites
Z320 Posted April 29 Report Share Posted April 29 Hi, I made a UNF/BSP adapter to fit a small BSP ball valve with a fiber washer between valve and block Ciao, Marco Quote Link to post Share on other sites
jimt Posted April 29 Author Report Share Posted April 29 22 minutes ago, BlueTR3A-5EKT said: Yes 1/2” unf Buy a short stainless steel head head screw and fit that with a sealing washer. Wrap a plastic bag round the starter motor when you drain the block via the plug to stop the electrics getting soaked …….. Thanks for confirming the thread in the later blocks. Thanks for the suggestion but the reason I want to fit a tap is I want to avoid the coolant going everywhere by fitting a long tube to it when draining - whilst I have a lathe etc and could easily do as you suggest - whilst a cheaper solution it still doesn’t result in what I want to achieve. Quote Link to post Share on other sites
BlueTR3A-5EKT Posted April 29 Report Share Posted April 29 47 minutes ago, Z320 said: Hi, I made a UNF/BSP adapter to fit a small BSP ball valve with a fiber washer between valve and block Ciao, Marco Good solution. Quote Link to post Share on other sites
jimt Posted April 29 Author Report Share Posted April 29 2 hours ago, BlueTR3A-5EKT said: Good solution. +1 You can also buy the 1/2 unf to 1/4 bspp converters and a 1/4bspp tail fitting for just a few pounds if you want to use the ball valve style tap Quote Link to post Share on other sites
Z320 Posted April 29 Report Share Posted April 29 not here at Germany Quote Link to post Share on other sites
jimt Posted April 29 Author Report Share Posted April 29 37 minutes ago, Z320 said: not here at Germany Ooh !! - Well easy enough to make if you have a screw cutting lathe with the correct change wheels and both thread form tools Quote Link to post Share on other sites
Z320 Posted April 29 Report Share Posted April 29 Or both dies… Quote Link to post Share on other sites
jimt Posted April 29 Author Report Share Posted April 29 14 minutes ago, Z320 said: Or both dies… even easier Quote Link to post Share on other sites
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