RichardS

So it could be the speedo head that is wrong rather than the pinion? I'm very unfamiliar with speedometer technicalities but if someone could tell me what the correct TPM is for a GT6 with overdrive and a 3.89 differential it would be very helpful. Assuming that the error I have is directly related to the TPM then I would have thought that I needed a speedo head which needs about 1180 turns for every mile? Although the rim sizes are now 14 inch, the tyre circumference is only 5 turns per mile larger than standard. Many thanks for all the ideas so far. Richard

I hope someone can tell me if I'm on the right track and whether there is a simple solution to this? My 1973 GT6 Overdrive has a standard 3.89 differential but has, at some point, been fitted with a recondition gearbox and overdrive unit. It all works well but the problem is that the speedometer and odometer and trip all read around 20% too high. The speedo head fitted is a Smiths 6211/00S 980. Is this the same speedo head fitted to all GT6's, overdrive and non-overdrive? The actual vehicle speed at 2500 rpm is 44mph in top gear and and 54mph with overdrive engaged. I believe these figures confirm that the problem here is that my overdrive and speedo drive must have been specified to work with a differential which is around 20% higher geared than mine. As my diff is 3.89:1, I suspect that my overdrive/speedo drive is designed to work with a diff which is around 3.2:1 Is there a Triumph model which has a gearbox and overdrive unit which is interchangeable with the GT6 but uses a 3.2 diff rather than a 3.9 diff? Looking at the Rimmers site, there is a speedo pinion part number 119100 for the non-overdrive car whereas the part number for the overdrive car is part number 506199. Does anyone know if I can simply buy the 506199 drive and swap out the drive pinion from my overdrive? All advice appreciated. Richard

Right, having received the post this morning, I think that we can finally put this thread to rest. 🙂 The photo below shows the yellow 1/8" BSP nipple on the left from Namrick and the silver 1/4" BSP from Rimmer on the right. It is obvious that these are both the same major diameter and thread pitch and are both, therefore, 1/8" BSP - 28 tpi as measured from the blanking plug. The Rimmer one is therefore mis-labelled both on their website and on the invoice. However, neither nipple is labelled totally correctly as the Namrick one is actually BSPT and the Rimmer one is actually BSPP. Both will fit, of course. 🙂

I dismantled the old bendix before I ordered the new one. With the press it's a two minute job, thankfully. There are so many different types that fit the Lucas M35J. 9 teeth, 10 teeth, clockwise, anticlockwise. I just hope I've ordered the right one, 9 teeth, clockwise, but we'll know in a couple of days. What is the Bosch recommended plug? This is another area where I haven't even started my research yet so I'll definitely start with this forum Richard

Thanks Pete I'm not sure what has been done over the years as there is a huge file of documents which I have only quickly scanned through. One interesting thing is a detailed valuation certificate from the TSSC dated January 1994. The valuation then was £2500 but, unfortunately, I paid a little more than that. ☹️ I whipped out the 1 and 6 plugs this afternoon and it's definitely running a bit rich, assuming that BPR6ES are the right plugs. However, I would expect it to be rich as it was on choke when I drove it onto the lift from cold a few days ago but at least the two were identical. I'll do a proper plug chop once I'm back on the road. The new fuel pump arrived today so I fitted it. It's completely different to the one that was fitted. 50% larger so needed some fuel pipe re-routing. I suspect that the original one was some kind of cheap rubbish where you couldn't even get a socket on the nuts because of the poor design. The new one from Rimmers, although cheap, is much more substantial and does have the inlet port integral with the cap which was the source of the fuel leak on the original. I also stripped down the starter motor today and have now ordered a new bendix as, although the flywheel looks new (I think that is in the paperwork) the teeth on the bendix were very worn such that there was no longer any ramp left on the leading edge. That's another postage charge! 🙁 So much to do .... so little time. 😉 Richard

That's very interesting Rob. I could certainly plumb my engine like that as it would not interfere with the brake booster. I wonder whether mine has been modified and the carb breathers blanked off because my engine has been fitted with a hotter cam and had the ports polished etc and blanking off the breather ports has been done to provide a richer mixture which would presumably be required to deliver the extra power? Does that sound plausible? Richard

Really helpful post David. I've ordered a 1/8 BSP from your link. I can see that I'm going to have quite a nipple collection in due course. Still, can't have too many, eh? 😕 Thanks Richard

Indeed Rob I've ordered the Rimmer one now in a much bigger order with some other stuff, so I'll report back once it arrives as that might help someone else. Richard

That's very true Doug. I could probably just jam the end of the grease gun in the hole and get a pretty good fill even without the nipple but I'll order it anyway and see. Richard

Thanks Pete .... but my engine appears to be newer than KE10000, in the 20000's in fact. The spigot in the top of my intake manifold is plumbed directly into the brake servo. I'm not sure where else it could go? I could presumably remove the blue bungs and pipe the carbs with a Y-piece into the rocker box if that is now it is meant to be, but the carbs will presumably have been set up with the current plumbing? It doesn't appear to be running rich but I haven't done much running yet. Richard

Thanks Pete I looked at the Rimmer fitting but I can't see how it can be 1/4 BSP as that has a larger diameter of around 13mm and a much coarser thread of 19 tpi. The blanking plug has a very fine thread which my thread gauge says is 27 or 28 tpi, although it's difficult to tell when it's this fine, and a major diameter of 3/8 inch or 10mm. This would suggest a 1/8 BSP fitting which has a major diameter of 9.7mm and 28 tpi but I cannot find a grease nipple which looks like that. Richard

I'm still in my first week of GT6 ownership so hope that someone will be able to help with this? Whilst I was changing the track rod ends yesterday I decided to grease the steering rack. It has a blanking plug but no grease nipple. I removed the plug and it definitely has been grease filled in the past. Possibly someone has switched from oil to grease like I did with my leaky Land Rovers? 🙁 Anyway, the blanking plug appears to be an imperial 3/8 diameter with 27 tpi. Can anyone give me a part number or web link for such an unusual size? The manual does refer to replacing the blanking plug with a grease nipple for greasing/oiling purposes so presumably one was available at some time? If there is no such part I can always drill and tap the blanking plug to take a more standard nipple but I'd prefer to source the correct part if possible. Many thanks Richard

Thanks Pete. I assume that the blue bungs on each carb are plugging the breather inlets? My engine has a rubber tube connected to a spigot on the side of the rocker box cover and that just runs down close to the bulkhead and vents to air low down. The open end is not particularly oily or dirty so I guess that there is little blow-by? I can't see any sign of a PCV valve or similar. Is there supposed to be something like that on late Mk 3's? Richard

Many thanks. I've only had the car for a couple of days and it's already up on the lift with lots of bits removed, which was not that easy as the narrow chassis rails and bolt-on body make it rather like Series Land Rovers which are also tricky to lift, but Strombergs are clearly something I will be learning about. I've already ordered the "adjusting tool" but I'm sure I'll need to make further appearances on here. 😊 First encounter yesterday with the drain-plug-free diff was also interesting. I managed to pump out all the old oil with the pump eventually but that will definitely be drilled and tapped in due course. Also found that the fuel pump looks exactly like the Rimmer replacement so that will be rebuilt with a new gasket. Both track rod ball joints were removed yesterday and replacements ordered and the threads re-cut. It looks as if someone had been gripping the thread with pliers to lock the rod in place. 🙁 The sump also appears to have been used to jack up the car so it is now leaking badly, as have the chassis outriggers just behind the front wheels, although not on the strong point where the crush tube/box lies but on the plate sections either side. ☹️ Are GT6 owners always this cavalier? 😕 Richard

Thanks Paul ..... I was thinking that there had to be a mechanical connection between the carbs in order for a choke flap on the inner carb to be closed. Maybe Strombergs don't work like that but enrich the mixture increasing fuel flow rather than by reducing air flow? I haven't stripped one down but I'll do some reading to fill in the gaps. Richard

After 40 years of being Spitfire and GT6 free, I've just re-invested in a 1973 Mk3 GT6. It runs and drives well but two things are immediately apparent to me. The first is that the engine smells of petrol and the second is that, although she starts immediately, the idle seems rather rough until she warms up. After some investigation this weekend, the petrol small clearly comes from the fuel pump which is weeping fuel. I assume that the fuel pump is the standard GT6 item, if there is such a thing, although it appears to be fairly new and does not have any markings on it. Please can anyone confirm exactly what model this is so I can determine which gasket kit I need? Secondly, it appears that the choke control only operates on the front 150 CDSE 3432 carb as can be seen in the photo, which presumably explains why the cold-running is rather rough until the back three cylinders get up to temperature. From reading other posts it appears that this single-choke arrangement is correct but I wonder whether there is an established practice of changing to twin choke operation? Many thanks for any help Richard