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Nick Jones

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Nick Jones last won the day on May 21 2020

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  • Location
    South Somerset
  • Cars Owned
    Vitesse Mk1 convertible with EFI, 5 speed and CV driveshafts
    GT6 Mk3 rotoflex - in restoration

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  1. What piston springs are fitted, if any? The mixture the engine sees is partly determined by the open jet area (in turn determined by the needle profile and piston position) and partly determined by the vacuum above the jet (determined my airflow and piston position). One of the most basic design calibrations of the CD carb design, SU or Stromberg, is to set the piston weighting (combination of actual weight and sometimes additional spring pressure) so that the piston is fully raised only at the engines maximum airflow demand. If the weight is insufficient, the main effect is that the piston will rise too much, vacuum above the jet will be low, and the mixture lean across the range. The secondary effect is that should you ever manage to find a rich enough needle that it appears to more or less work, you will then find that once you get to a certain rev/throttle combination, the carb piston is prematurely fully raised, and it looses its ability to control, the vacuum increases and the mixture goes uncontrollably rich. 150CD carbs are just big enough for a 2L @6000rpm, with not much margin for extra flow. They’ll support maybe 120bhp without resorting to “restricted inlet” type tuning tactics. This doesn’t automatically mean they are too small for any 2.5. If you are not expecting to rev your 2.5 much beyond 4.5 - 5k rpm they’ll be fine, provided they are correctly calibrated. Nick
  2. I’m guessing but a bare chassis is an easy two man lift so maybe 70kg? Nick
  3. I use them without washers which I’m fairly sure is how they are used on Minis but using proper hardened washers as well shouldn’t do any harm. Nick
  4. Given you’ve confirmed fuel to the carbs and there are two them…. Why are we not thinking this could be an ignition problem? Coil, condensor, rotor arm? I have had the latter give very similar symptoms. Nick
  5. What is real tight at 15 - 20C may be rather less tight when the pump body is warmed to 60C…… Just saying…. Pleasing to hear that the new valves bring an obvious improvement. I wonder how many cars there out there with vapour lock issues may far worse by marginal valves….. Nick
  6. Which is bang in the middle of the range I posted earlier from the FWD manual….. Thanks for confirmation Martin. Nick
  7. Your are trying to mimic the Spit Mk3 arrangement with the larger cam-way bore (50mm nominal) and smaller cam journals with wrapped bearing shells between them. There the block needs boring out to 4 cylinder block specs as shown below in this extract from a 1300 FWD O&M
  8. Is the shaft it came off still straight? Took a fair thump to do that damage…. Nick
  9. They usually have a magnetic plug with a 3/4” hex head. Though as already observed, that looks more like a case of cross threading. Nick
  10. Ok. So is this actually an FD small-crank on the first few hundred, using up stocks, or something more widespread? Or is it a big crank FH with the Mk3 cam. I’ve never seen one (not surprising) and I don’t know anyone who has. As it happens, our earlyish MkIV does have a full FD engine. But only because we created it specially. The car came with a large crank FH. Didn’t measure the cam but it had no cam bearings. Nick
  11. May well be right about Spit Mk2, but I think the early MkIV thing is a myth. Nick
  12. Nooooo! I had a machinist who thought that would be an ok approach and two of the bearings came out while I was fitting the cam. I can tell you that on the 4 cylinder 1300 & 1500 engines, all camways are bored to the same size so you can fit shells or not to suit your cam. Only the Spit Mk3 and 1300TC FWD had them from the factory though. Nick
  13. Sounds like the exhaust manifold is blowing at the head /manifold joint to me Nick
  14. RAL3016 or RAL2002 according to the internet….. the latter possibly on “more recent” product. Don't worry, I’m not sure the concours judges carry paint swatches 😜 Nick
  15. Hi Wim, I think we put the join at the bottom on both the Spitfire and GT6. It shows less there but I don’t think it makes any practical difference. Ni
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