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MG MGA - Carb spacer blocks - needed?


I've got a manifold for HS6 carbs, but the studs are only long enough to alow the paper gasket, the heatshield and the carb and securing nut to fit. On the original A manifold, there was a spacer block, and on some HS6 fits I have seen spacer blocks (the black heatproof plastic bits).

Does fitting (or not fitting) add any performance advantage?


Grant :-)
G Hudson

They prevent fuel vapourizing in the carbs due to heat. Why not replace the studs with longer ones?
Art Pearse

Hi Art,

thanks for that. Makes sense to keep the carbs cool. replacing the studs sounds easier than it is - I'm trying to find studs that are 1/4 UNF and the same length (ish) as the A studs. Most studs seem to be 5/16, and I don't really want to drill the carbs and manifold to fit the wider diameter studs.


Grant :-)
G Hudson

All HS carbs have holes for 5/16 studs, and so all manifolds I've ever seen have 5/16 studs. If you have one with 1/4" studs, it is bizarro!

FR Millmore

The carb spacers and the heat shield are important to isolate and shield the carbs from the heat of the engine and exhaust manifold. A cooler mixture is denser and more consistent than a warmer mixture.

The cool air duct from the grill to the carburetors is also important in that regard.

The carb spacers also establish the distance from the front of the carbs to the valve, an important but not critical element in the design of the intake system. Changing the intake runner length changes the torque peak point of the power curve. Shorter raises the torque point, longer lowers the torque point. Same effect goes for the exhaust manifold.
Russ Carnes

This thread was discussed between 17/07/2009 and 18/07/2009

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