Nigel Wilcox Posted March 9, 2008 Report Share Posted March 9, 2008 I need to buy a stainless system for my Doretti which may or may not include a tubular manifold. I am using a TR4 high port head and a fairly standard TR4a engine albeit with 87mm pistons. The original system used two in line 18inch oval silencer boxes. I will be using the car for long distance touring so I do not want intrusive noise, on the other hand I want plenty of go! Does anyone have any recommendations for a system which will fit? - Phoenix, Triumph tune, or possibly a late TR4a manifold (306378) which has a twin outlet - is there a system to mate to this with 2 silencers forward of rear axle? thanks. Nigel Quote Link to post Share on other sites
Alec Pringle Posted March 9, 2008 Report Share Posted March 9, 2008 Hi Nigel, When I bought a Doretti, back in '75, it came with a brace of TR2/3 'long' silencers in line - didn't exactly sound too sporty, and they were rotting anyway . . . Chucked 'em away and replaced with a brace of 'short' tail boxes, chopping up pipe to fit as necessary - great improvement in tone and tune ! Personally I'd forego the stainless option in favour of mild steel. OK, it rusts, but it has more silencing effect for the weight and without the horrible tinny resonance that so many cheaper stainless systems feature. I find it's the resonance effect that's fatiguing on long journeys, not the actual sound level. Cheers, Alec Quote Link to post Share on other sites
vivdownunder Posted March 10, 2008 Report Share Posted March 10, 2008 Hi Nigel, Regarding the power output of your engine, after your 87mm pistons, the next most gain comes from the camshaft grind and headwork. A good exhaust compliments these in the overall efficiency equation, rather than giving you bulk power on its own account. If you fit the 4A dual outlet exhaust manifold, you will need a "two into one" engine pipe to get through the chassis cross member. You would need to check if the standard Moss 4A engine pipe of this configuration (HRSU1358) fits through the cross member of your chassis. Hopefully it will be OK. Next comes the first muffler, and I suggest to beware some mainstream suppliers, as they have been using a first muffler that is far too big in diameter. It has to be cut down to fit at a front corner, doesn't match the level of the inlet pipe at the cross member, and puts a lot of heat into the floor of the car. What I recommend is a 20"x5"x3" straight through type muffler that will fit easily in front of the diff. (I use this size muffler alone with Triumphtune extractors and the note is just right for me) Finally, fit a plain tailpipe and test the car to see if you like it. If you want it quieter, then fit a 12"x5"x3" straight through muffler into the tailpipe behind the diff. Hence, after the engine pipe, I suggest using a local exhaust shop to make up the rest of the system. Regarding stainless, as Alec says, the note is often disappointing. It's the muffler rather than the pipes that rust out, but the coating on the mild steel mufflers is very good these days, and they generally last a lot longer. Much cheaper too, so more left for other things!. You can keep new pipes from rusting externally by spraying before fitting with heatproof ally paint from a can. To answer your question on the expected power difference between the 4A dual manifold and extractors, then you would expect the extractors to win out, but the cast manifold is quieter and generates less heat in the engine bay, so it's a trade off. Hope this helps, Viv. Quote Link to post Share on other sites
stuart Posted March 10, 2008 Report Share Posted March 10, 2008 If you want to extend the life of a new standard steel exhaust, tape over one end and pour some cold galvanising paint in and turn round and round until its all coated internally and then drain off the excess allow to dry and this will add 20 yrs to the life of it. Stuart. Quote Link to post Share on other sites
Nigel Wilcox Posted March 10, 2008 Author Report Share Posted March 10, 2008 (edited) Hi Nigel, When I bought a Doretti, back in '75, it came with a brace of TR2/3 'long' silencers in line - didn't exactly sound too sporty, and they were rotting anyway . . . Chucked 'em away and replaced with a brace of 'short' tail boxes, chopping up pipe to fit as necessary - great improvement in tone and tune ! Personally I'd forego the stainless option in favour of mild steel. OK, it rusts, but it has more silencing effect for the weight and without the horrible tinny resonance that so many cheaper stainless systems feature. I find it's the resonance effect that's fatiguing on long journeys, not the actual sound level. Cheers, Alec Thanks Alec I too have poor experiences of some stainless systems. I once resorted to wrapping an Elan tailbox with a B&Q fire blanket before wrapping that with exhaust wrap designed for manifolds. It certainly helped but I was never entirely happy with the outcome. On another occasion I had a Scimitar with twin stainless back boxes which sounded great for the first half mile but thereafter became intolerable. Regards Nigel Edited March 10, 2008 by Nigel Wilcox Quote Link to post Share on other sites
Nigel Wilcox Posted March 10, 2008 Author Report Share Posted March 10, 2008 Hi Nigel, Regarding the power output of your engine, after your 87mm pistons, the next most gain comes from the camshaft grind and headwork. A good exhaust compliments these in the overall efficiency equation, rather than giving you bulk power on its own account. If you fit the 4A dual outlet exhaust manifold, you will need a "two into one" engine pipe to get through the chassis cross member. You would need to check if the standard Moss 4A engine pipe of this configuration (HRSU1358) fits through the cross member of your chassis. Hopefully it will be OK. Next comes the first muffler, and I suggest to beware some mainstream suppliers, as they have been using a first muffler that is far too big in diameter. It has to be cut down to fit at a front corner, doesn't match the level of the inlet pipe at the cross member, and puts a lot of heat into the floor of the car. What I recommend is a 20"x5"x3" straight through type muffler that will fit easily in front of the diff. (I use this size muffler alone with Triumphtune extractors and the note is just right for me) Finally, fit a plain tailpipe and test the car to see if you like it. If you want it quieter, then fit a 12"x5"x3" straight through muffler into the tailpipe behind the diff. Hence, after the engine pipe, I suggest using a local exhaust shop to make up the rest of the system. Regarding stainless, as Alec says, the note is often disappointing. It's the muffler rather than the pipes that rust out, but the coating on the mild steel mufflers is very good these days, and they generally last a lot longer. Much cheaper too, so more left for other things!. You can keep new pipes from rusting externally by spraying before fitting with heatproof ally paint from a can. To answer your question on the expected power difference between the 4A dual manifold and extractors, then you would expect the extractors to win out, but the cast manifold is quieter and generates less heat in the engine bay, so it's a trade off. Hope this helps, Viv. Thanks Viv Looks like it's 3 votes for mild steel - at least for the silencers. As you say, I will probably have to suck it and see. Whichever way I go it looks like it's time to set up a direct debit with Messrs Moss! Regards Nigel Quote Link to post Share on other sites
Nigel Wilcox Posted March 10, 2008 Author Report Share Posted March 10, 2008 If you want to extend the life of a new standard steel exhaust, tape over one end and pour some cold galvanising paint in and turn round and round until its all coated internally and then drain off the excess allow to dry and this will add 20 yrs to the life of it.Stuart. Thanks Stuart 20 years - yes that should be enough, I'll be too old to do my own maintenance by then but I expect I'll still try. I imagine that it would be stove enamelled internally after about 20 minutes running. Regards Nigel Quote Link to post Share on other sites
stuart Posted March 11, 2008 Report Share Posted March 11, 2008 Thanks Stuart20 years - yes that should be enough, I'll be too old to do my own maintenance by then but I expect I'll still try. I imagine that it would be stove enamelled internally after about 20 minutes running. Regards Nigel Something like that! Thats an old trick learnt from Jaguar XK owners many years ago before the advent of stainless systems as the 120s would consume steel silencers for a pastime! Stuart. Quote Link to post Share on other sites
Menno van Rij Posted March 16, 2008 Report Share Posted March 16, 2008 (edited) Next comes the first muffler, and I suggest to beware some mainstream suppliers, as they have been using a first muffler that is far too big in diameter. It has to be cut down to fit at a front corner, doesn't match the level of the inlet pipe at the cross member, and puts a lot of heat into the floor of the car. ... just as I found out the hard way! Next time I'll turn to a local motor cycle shop and I'll buy one (or two) motor cycle mufflers: sleak and hard wearing. Not the bl**dy item I've fitted for now. I'm not going to make that mistake again! Just look at the homepage of my website, then you'll see for yourself! Menno Edited March 16, 2008 by Menno van Rij Quote Link to post Share on other sites
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