james christie Posted November 27, 2019 Report Share Posted November 27, 2019 (edited) Can some kind soul give me the thread type for the 1" aluminium core plug for the 4 cylinder engines. Part N° PS 1603, I believe. I need to order a tap to tidy up the thread. UNC ? thanks james Edited November 27, 2019 by james christie Quote Link to post Share on other sites
RogerH Posted November 27, 2019 Report Share Posted November 27, 2019 Hi James, I am sure I have these in a box in the garage. I'll measure tomorrow and get back to you. Roger Quote Link to post Share on other sites
RogerH Posted November 28, 2019 Report Share Posted November 28, 2019 Hi James, I've just checked my screw in plugs and realise they are for the oil gallery ends on the block. these are 3/4 x 16 tpi = 3/4 unf if yours is 1" diameter then I would put money on it being 1! x 12 tpi = 1"unf Roger Quote Link to post Share on other sites
roy53 Posted November 28, 2019 Report Share Posted November 28, 2019 i take it you meen the water plug in the centre of the head. i managed to clean the thread up with a wire brush in a drill and fitted the replacement plug from moss with suitable sealant . All ok Roy Quote Link to post Share on other sites
BlueTR3A-5EKT Posted November 28, 2019 Report Share Posted November 28, 2019 Yes PS1603 is 1" NF thread Just look in the Standard Triumph hardware catalogue.... https://www.canleyclassics.com/standard-triumph-hardware-catalogue-plug-core-screwed Peter W Quote Link to post Share on other sites
james christie Posted November 28, 2019 Author Report Share Posted November 28, 2019 Thanks for this info. Yes it is the aluminium (coolant) plug in the centre of the cyl head I had an unsuccessful attempt at cleaning the thread with a wire brush. The plug won't screw fully home and as it is in aluminium I don't want force it. To save me from a mortal end in ignorance can you trained mechanics explain the difference between UNF and NF? james Quote Link to post Share on other sites
RogerH Posted November 28, 2019 Report Share Posted November 28, 2019 Hi James NF is essentially the same as UNF. NF was put to bed in the late 40's early 50's - try finding one now. Even if the TR heads did have the NF form from its Vanguard ancestry it would still be UNF you need. Roger Quote Link to post Share on other sites
james christie Posted November 28, 2019 Author Report Share Posted November 28, 2019 Many thanks, Roger. Now to find a 1" UNF tap in France....... james Quote Link to post Share on other sites
BlueTR3A-5EKT Posted November 28, 2019 Report Share Posted November 28, 2019 1 hour ago, james christie said: Many thanks, Roger. Now to find a 1" UNF tap in France....... james Tracy tools They will ship anywhere the basic tap is under £10.00 https://www.tracytools.com/taps-and-dies/UNF-taps/1-x-12-tpi-unf-spiral-flute-point Peter W Quote Link to post Share on other sites
RogerH Posted November 28, 2019 Report Share Posted November 28, 2019 +1 for TRacy Tools. yesterday at apprx 3pm I ordered a 8mm x 0.75 pitch. It arrived at 10.30 am this morning. Roger Quote Link to post Share on other sites
roy53 Posted November 29, 2019 Report Share Posted November 29, 2019 20 hours ago, james christie said: Yes it is the aluminium (coolant) plug in the centre of the cyl head. The plug won't screw fully home and as it is in aluminium I don't want force it. james Are these plugs not tapered ? so will not go fully home. Will check on this when i get to the garage. Roy Quote Link to post Share on other sites
BlueTR3A-5EKT Posted November 29, 2019 Report Share Posted November 29, 2019 If the thread goes all the way into the water way what stops the plug from screwing all the way in and being lost? The thread in the head may be tapered. In which case I would say .....DO NOT CLEAR THE THREAD IN THE HEAD WITH A TAP. Or the plug may not seal. The tightness you are feeling after a couple of turns of the new plug may be the tapered thread binding on the plug and making a seal. Peter W Quote Link to post Share on other sites
BlueTR3A-5EKT Posted April 22, 2022 Report Share Posted April 22, 2022 UPDATE. Following this saga as to what thread the plug PS1603 should be It should be 1” x 14 tpi National Fine. Pete(BFG) has been sold a plug that is 1” UNF x 12 tpi that will not screw into his head. It is the wrong pitch thread for a TR cylinder head, which is tapped 1” NF x 14 tpi. Moss know about this issue as they had them made wrongly and had them rejected by their customers in the USA. Cheers Peter W Quote Link to post Share on other sites
james christie Posted April 22, 2022 Author Report Share Posted April 22, 2022 “sold a plug that is 1” UNF x 12 tpi that will not screw into hishead”. Yes, I have first hand experience of this!. In reality the 12tpi into a 14tpi jams up and seals pretty well after a few threads have been wound in, especially if helped with a liberal dose of araldite or whatever it’s called nowadays. But why can’t our suppliers get it right before they flog us this **** ?? james Quote Link to post Share on other sites
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