[TR] Cylinder heads

[Rick]

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.

 

The 3A runs great, by the way, with this change, a 4A cam grind, and 4A
cylinder linings and pistons.

 

 Rick in Seattle

 

1960 TR3A

1970 BSA 441 Victor

1972 Norton 750 Commando Combat

1975 Norton 850 Commando Mk3

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