Bits and Pieces

Heat Shields for T-Types

The following explanation from Barrie Jones, TD/TF Technical Specialist for the T Register of the MGCC to an enquirer for a TD heat shield gives some useful background information about the development of his heat shields and the reasons for their lack of application to the TD.

I originally developed my heat shield for the TF. It fits and it works. Fortunately, the TF was originally fitted with spacers between the H4 carbs and inlet manifold. (MGA spacers are even better).

I then modified my heat shield to fit a TC, which uses smaller H2 carbs (same as a TD). It did not fit because the TC carbs fit closer to the manifold, so my shield fouls the manifold clamps and the accelerator lever. I then added some 12mm spacers between carbs and manifold, and now it fits and it works. This arrangement also fits a TB.

So far I have manufactured 100 of these kits and I only have 8 left, with no complaints and several complimentary e-mail reports.

I have tried to fit my TC system to several TDs, but I experienced the following problems:

  1. The original air intake system runs immediately above the inlet manifold, so the heat shield needed a big chunk cut out of it.

  1. With the heat shield fitted, you cannot access the nuts on the steady bar that supports the air intake tube above the inlet manifold.

  1. If your TD has a 5-speed gearbox conversion, this throws the engine forward and that does not leave enough room for the carbs plus my spacers.

    For a TD I therefore recommend the heat shield marketed by Brown & Gammons (see link below), but I must warn you that I have my doubts about using such a shield without spacers because the TD float chambers will still sit too close to the exhaust manifold.

    http://www.ukmgparts.com/product/td-midcat-8-td7-carburettors/heatshield-tc-td-tf-gac1036

    Ed’s note: I have a small stock of both TB/TC heat shields plus spacers and also a few TF heat shields which are on their way to me from Barrie. I supply these on a non-profit making basis as a service to TTT 2 readers. The TB/TC heat shields are £15 each plus £5 each for the spacers (two required) plus postage at cost. The TF heat shields are likely to be the same price but will be confirmed at time of ordering.

    Also on their way to me are several copies of Barrie’s Notes (see the T-Shop for details). The main print run of 1000 sold out, so a small batch has been printed. I have back orders on hand.

    Clocks in TDs and TFs (from Russell Dade)

    “Having owned my TD for 53 years and not worrying about the car clock very much I was suddenly reminded that it could be quite useful!; however my clock had not worked since I first purchased the car.

    Recently, whilst driving on a Social Run with the Austin 7 Essex Car club I needed to look at my watch for the time, as I had made a date for lunch with my wife. I discovered that with a buttoned shirt cuff and a Jacket I could not stretch my arm enough to look at my watch and steer the car, so I decided that the time had come to fix that tiny timepiece.

    On removing the rev counter I discovered that it did not have a lead? ie no power!

    “Easy” I thought, so I looked up the wiring diagrams for TD/TFs – Nothing!

    Checked various web sites and very soon realised that this little clock has been discussed by all and sundry and the wiring was a simple lead from the feed side of the Ammeter, or Inspection socket or a lead from the “A” terminal on the control box.

    So after sorting out the power lead to the “clock”- Nothing!

    Well, I have only owned the car for 53 years with the clock sitting there grinning at me knowing that it needed a power lead and also knowing that it was getting bunged up with dirt!

    This is where Totally T-Type 2 comes in – I remembered that an old edition of the mag. had mentioned David Ward as a useful man when it came to our little clocks and so emailed him and arranged for him to repair it.

    He explained that he does not carry spares for these clocks, but has the knowledge and ability to adjust, clean and get them running again and that’s exactly what he did with my superannuated time piece, he cleaned it and adjusted it and ran it for approximately a week on his work bench.

    I refitted the rev counter complete with its clock and refitted the battery lead, adjusted the time and gave the tiny control wheel a twist and the clock was a runner!!

    The ticking of the clock is rather satisfying on hearing it for the very first time, a simple pleasure, but after all those years rewarding.

    So after the 53 years rest, I expect the clock to outlast me, although time is running!

    David Ward is only interested in covering his costs so is generous with his time; I would recommend him as an MG ambassador.

    It may be that they are not connected??

    Thanks for your great little magazine”.

3 thoughts on “Bits and Pieces

  1. Peter Vielvoye says:

    Ed Biddle well respected carb expert told me when inquiring about the shield in my YT that the spacers should be kept to a bare minimum as the further away from the combustion chamber they are the more the vapourisation of the mixture breaks down. If you can get away with building up gaskets you are more likely to maintain performance.
    Peter

  2. JOHN JAMES says:

    Barrie Jones has commented as follows:

    Vaporisation is not the problem that I am addressing.

    The problem is that Ethanol has been added to modern petrol and it boils at 78 degrees C.

    The float chambers on the TB/TC/TD (and the YT) sit very close to the exhaust manifold.

    My spacers double the distance between exhaust manifold and float chamber.

    Radiated heat is proportional to the square of the distance.

    Therefore, using my spacers reduces the amount of heat received from the manifold by a factor of 4 and the heat shield adds a further improvement.

    You should also notice a small improvement on low speed torque due to the longer inlet tracts.

    Therefore, on balance, I prefer to add the spacers.

    • Ian McCulloch says:

      Re Barrie’s comment about ethanol, does using top grade petrol help – I gather that many of these do not contain ethanol? Also, does adding a lead substitute such as Castrol Valvemaster have any effect? I have been told that it does, but can’t immediately see why!

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