Aitch Posted November 30, 2021 Report Share Posted November 30, 2021 I have a 1979 Spitfire 1500 with o/d. I have just replaced the clutch slave cylinder having accessed it through the Gearbox tunnel cover (no problems there). Underneath the tunnel was a plastic wrapped insulation. Looks like an original part. I cannot seem to find that this insulation is, (1) an OEM part? (2) An aftermarket part? (perhaps even something a previous owner(s) have fitted?). If I cannot replace it could I use something like a 6mm sound deadening material on the underside of the tunnel cover. Any suggestions much appreciated? Link to comment Share on other sites More sharing options...
Colin Lindsay Posted November 30, 2021 Report Share Posted November 30, 2021 The original soundproofing was plastic wrapped stuff that has probably deteriorated over the years. A good thermal coat such as Dodomat or Hexmat stuck onto the clean tunnel cover will work wonders with both heat and noise. I did it on my last Gt6 and it took about eight sheets, but saw an amazing drop in the heat given off. Link to comment Share on other sites More sharing options...
Aitch Posted November 30, 2021 Author Report Share Posted November 30, 2021 Thanks, Colin, that looks like a very suitable option. I shall do some recce. Link to comment Share on other sites More sharing options...
dougbgt6 Posted November 30, 2021 Report Share Posted November 30, 2021 A lot of us use SilentCoat, works very well. you'll only need 5-6 sheets for the tunnel, Doug Link to comment Share on other sites More sharing options...
Peter Truman Posted November 30, 2021 Report Share Posted November 30, 2021 Similarily I must do the Spitfire in it's upcoming overhaul, the Vitesse was done with Dynamat, fortunately I had the ultimate supply, free offcuts from an industrial plant upgrade, I overkilled it as I had plenty so did both the underside and top of the replacement fibreglass tunnel, a great improvement. Link to comment Share on other sites More sharing options...
JohnD Posted December 1, 2021 Report Share Posted December 1, 2021 It's worth repeating my experience with the Silverback. That had the radiator in the back and was a cold car to drive. All the unwanted heat comes in the form of hot air from a front radiator, leaking into the driving compartment. There are dozens of holes in the bulkhead, and the gearbox cover can be difficult to seal to the floor. Sort all those, and you may not need Insulation! John Link to comment Share on other sites More sharing options...
dougbgt6 Posted December 2, 2021 Report Share Posted December 2, 2021 On 01/12/2021 at 15:10, JohnD said: There are dozens of holes in the bulkhead, and the gearbox cover can be difficult to seal to the floor. Sort all those, and you may not need Insulation! Why go to all the trouble of patching up the bulk head and NOT insulate the tunnel? db Link to comment Share on other sites More sharing options...
Clive Posted December 3, 2021 Report Share Posted December 3, 2021 On my (ford engined/box) spit, I had to make a bespoke tunnel. The sheet steel was supplied by a filing cabinet, pretty thin, but powder coated. Strength comes from a few angles as I chose to make it out of flat sections. I lined the tunnel with 6mm thick closed cell foam, stuck on with PU adhesive (like tigerseal) and for simplicity, carpet is stuck with contact adhesive to the outside. I have a 65mm hole cut for checking the gearbox oil. First big trip was to Spa, all was well on teh way there, and the tracklaps (we surprised many many TR's, and got within a smidge of lapping our friend in his stag, not bad in a 20min session) However, on the way home the plastic cover for the oil filler hole disintergrated. This was a disaster, as the air coming out was VERY hot, akin to a hot air gun. It made the car unbearable, and we had to pull over. We looked for a solution, and my passenger dscvered his stainless flask cup/lid jammed in teh hole perfectly. Job done! But John is correct in that any holes/gaps will cause misery. Sort those first, and insulate after. In fact the old card tunnels are better than fibreglass or ABS for heat. And the old insulation works pretty well IF fixed correctly, which it usually isn't. The other issue I have is teh 2 1/4" exhaut runs close to the bodywork, and does warm the floor nicely. However, my latest "fiddle" has the pair of secondary pipes running under the front "cutout" of the sump, so there is about 20" extra pipe to get rid of some of the heat before it gets to my feet. Time will tell on that (it has perked the car up a tad getting the manifold dimensions correct, I just copied the Ford performance manifold lengths) Can you tell that I hve some time on my hands? sorry for wittering. Link to comment Share on other sites More sharing options...
JohnD Posted December 3, 2021 Report Share Posted December 3, 2021 Doug, I think Clive has shown better than I could the importance of a well sealed bulkhead, an gearbox cover! As to why insulate after you have sealed, cost and bother, neither of which may be necessary! Link to comment Share on other sites More sharing options...
dougbgt6 Posted December 3, 2021 Report Share Posted December 3, 2021 John, And I think, why spoil the ship for 1/2p worth of tar? Doug Link to comment Share on other sites More sharing options...
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