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</o:shapelayout></xml><![endif]--></head><body lang=EN-US link="#0563C1" vlink="#954F72"><div class=WordSection1><p class=MsoNormal>I fitted my TR3A with a TR4A exhaust manifold and exhaust, and can speak to the “interchangeability” of the manifolds. The TR4A exhaust manifold will interlace ONLY with a TR4A intake manifold. Because of the longer throat of the 4A intake manifold, it really requires HS6 carbs (short throat). Fitting the original carbs to the 4A manifold requires substantial “modification” to the wheel well sheetmetal to allow for the air boxes. In short, fitting a 4A exhaust manifold to a TR3A requires both a 4A intake manifold AND new carbs and linkages. Other than that, it’s an easy mod.<o:p></o:p></p><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal>The 3A runs great, by the way, with this change, a 4A cam grind, and 4A cylinder linings and pistons.<o:p></o:p></p><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal><span style='font-size:12.0pt;font-family:"Times New Roman",serif'> Rick in Seattle<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:12.0pt;font-family:"Times New Roman",serif'><o:p> </o:p></span></p><p class=MsoNormal><span style='font-size:12.0pt;font-family:"Times New Roman",serif'>1960 TR3A<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:12.0pt;font-family:"Times New Roman",serif'>1970 BSA 441 Victor<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:12.0pt;font-family:"Times New Roman",serif'>1972 Norton 750 Commando Combat<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:12.0pt;font-family:"Times New Roman",serif'>1975 Norton 850 Commando Mk3<o:p></o:p></span></p></div></body></html>