ijonsson Posted August 6, 2020 Report Share Posted August 6, 2020 2 hours ago, Brian Eldred said: John, Ian, I did both yesterday afternoon (I too used an old screwdriver with the handle cut off), remembering to spin anti-clockwise, and then got 50 psi on cranking. The engine fired up on first push of the button, ran a bit rough for a few seconds, on 3 cyls I think, then refused to start again. Carb pistons were sticking, and I think I flooded it. I read on here about how wet plugs can die, so am getting some new ones later today. Thanks for all the advice from you knowledgeable people! Brian You can make wet plugs as new heating them red hot with a blowtorch/gas burner Quote Link to post Share on other sites
Bfg Posted April 21, 2022 Report Share Posted April 21, 2022 (edited) On 8/4/2020 at 10:17 AM, Brian Eldred said: Well it's sorted at last. I cleaned the thread with the tap, cut a slot in the top, applied Locktite 577 and screwed it in. For info the thread is 1" UNF 12 tpi, and if anyone else needs to do the same job I have a tap to lend/sell! Thanks, Brian Thank You Brian. For your, and other's, information - I've just been through this with my TR4A < here > that's fitted with, I believe, a TR4 cylinder head. And after a lot of back n' forth - I've got a bolt which fits . . . ^ Naturally this will need to be cut a little shorter ! ..but the important thing is that the thread fits the TR4 cylinder head (..this head was exchanged by the prior owner for unleaded ). And this bolt's thread is 1" x 14 tpi ..and not the 1" x 12 tpi of the aluminium core plug I had supplied. Although Brian also has a TR4A, the engine he was working on is a TR2, ..so presumably the specification of these core plugs changed inbetween times. I will chop this bolt to 1/2" in length and use that as the core plug. Btw it cost £4 from Suffolk Fasteners, Ipswich (who also post fasteners out), and it has enough thread to make three or four core plugs from, which are less prone to corrode through in just 55 years ! Or if the threaded hole in the head is difficult to clean out, then simply a hacksaw vertical slot in the side of this bolt, and that ought to clean out the oxidised aluminium very easily. Hope that helps other readers. Pete Edited April 21, 2022 by Bfg Quote Link to post Share on other sites
RogerH Posted April 21, 2022 Report Share Posted April 21, 2022 Hi Pete, The SAE thread form was used before the unification of UK, USA & Canada. The 1" SAE is indeed 14tpi 1" UNF - 12tpi 1" UNC = 8 tpi. Could your TR4 head actually be something in the age frame of an Vanguard Roger Quote Link to post Share on other sites
Bfg Posted April 21, 2022 Report Share Posted April 21, 2022 (edited) Hi Roger, As far as I 'guess' it's a TR4 high port head. The only external difference between it and the TR4A ..that I am aware of, is that the flat with head number stamped on it, by #1 exhaust port, is absent and the push-rod tubes are ferrous steel rather than aluminum. . . ^ Katie's cylinder head with its new (1/2"-deep steel) core plug fitted. There was no indication that the thread had been re-cut, and the old plug, if I recall correctly, had STAN 31 stamped into it. ^ as far as I can ascertain, the stamped head number reads 3151. I don't know if the casting numbers T276 and the capital letter 'M' (by the distributor) offer any further clues. Pete Edited April 21, 2022 by Bfg Quote Link to post Share on other sites
Drewmotty Posted April 21, 2022 Report Share Posted April 21, 2022 2 hours ago, Bfg said: And this bolt's thread is 1" x 14 tpi ..and not the 1" x 12 tpi of the aluminium core plug I had supplied. I had this problem recently when rebuilding my TR4 engine. The “stick” of plugs I had didn’t fit the head. I ended up machining up a plug on my baby Myford. Quote Link to post Share on other sites
Bfg Posted April 21, 2022 Report Share Posted April 21, 2022 And the thread you cut was also 14 tpi ? Quote Link to post Share on other sites
RobH Posted April 21, 2022 Report Share Posted April 21, 2022 Perhaps it could be 3/4 BSP? Major diameter 1.04 ins x 14 tpi so slightly over-size but not much. Quote Link to post Share on other sites
Bfg Posted April 21, 2022 Report Share Posted April 21, 2022 7 minutes ago, RobH said: Perhaps it could be 3/4 BSP? Major diameter 1.04 ins x 14 tpi so slightly over-size but not much. Nope tried that, I bought new fittings including a 3/4" BSP capping plug ..and it don't go in (to this cylinder head). This bolt's thread is definitely 1" x 14 tpi and that finger screwed in. It's a bit sloppy to be honest, but then I have been brutally power-wire-brushing that inside thread to try and get it clean enough for the supplied core plug (with 12 tpi) to get further than two turns in. Quote Link to post Share on other sites
ntc Posted April 21, 2022 Report Share Posted April 21, 2022 Call me old school but oil and water don’t mix and unless you rebuild the engine the damage is already done. Quote Link to post Share on other sites
Lebro Posted April 21, 2022 Report Share Posted April 21, 2022 Looks like a TR3 head to me Triumph TR2-3B FAQ _ Triumph heads.html Bob Quote Link to post Share on other sites
Bfg Posted April 21, 2022 Report Share Posted April 21, 2022 As far as i am aware the TR4 also had no flat there, and that was introduced with the 4A head. see also < here > Pete Quote Link to post Share on other sites
RogerH Posted April 22, 2022 Report Share Posted April 22, 2022 Hi Pete, Pete Wigglesworth has posted (today) to say that the thread SHOULD be 1" x 14tpi The SAE rating is for a NF thread. Apparently MOSS got this wrong and have been informed - quite some time ago. Roger Quote Link to post Share on other sites
BlueTR3A-5EKT Posted April 22, 2022 Report Share Posted April 22, 2022 2 hours ago, RogerH said: Hi Pete, Pete Wigglesworth has posted (today) to say that the thread SHOULD be 1" x 14tpi The SAE rating is for a NF thread. Apparently MOSS got this wrong and have been informed - quite some time ago. Roger 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
Bfg Posted April 22, 2022 Report Share Posted April 22, 2022 Is this a spec change from the earlier cars ? ie., Brian Eldred's TR2 Quote Link to post Share on other sites
Bfg Posted April 22, 2022 Report Share Posted April 22, 2022 20 minutes ago, BlueTR3A-5EKT said: Pete(BFG) has been sold a plug that is 1” UNF x 12 tpi that will not screw into his head. it wouldn't go into Katie's either ! Quote Link to post Share on other sites
Drewmotty Posted April 22, 2022 Report Share Posted April 22, 2022 (edited) .. Edited April 22, 2022 by Drewmotty Double post Quote Link to post Share on other sites
iain Posted April 22, 2022 Report Share Posted April 22, 2022 Revington sell the correct version……well,it certainly fitted my engine with no issue at all. Iain Quote Link to post Share on other sites
Brian Eldred Posted April 27, 2022 Author Report Share Posted April 27, 2022 I just found the tap I used. The plug came from Revington. Just to add to the confusion Brian Quote Link to post Share on other sites
Bfg Posted April 27, 2022 Report Share Posted April 27, 2022 I never doubted you, we might only presume the spec changed inbetween the build of your TR2 and my TR4 (cylinder head). When or why is another matter all together Quote Link to post Share on other sites
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