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Post by jonnyb on Sept 11, 2023 19:11:56 GMT
My car has a 4psi pressure cap and and runs fine and doesn't seem to lose any coolant. I have an official BMC WSM which suggests a 4 psi cap and also an Owners Workshop Manual by JRS Hall which suggests 7 psi. I think the MGA and early MGB used 7 psi caps. The club sells 4psi and 7psi caps. Interesting too that the Riley cooling system has a 13 pint capacity system while MGA/B were between 9.5 and 11.5 pints. What do all your cars have?
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Post by vue from the north on Sept 11, 2023 21:12:17 GMT
i recall a conversation with someone about this that went along the lines of the later 5 bearing crank engines had a higher pressure cap than the earlier 3 bearing cranked engines,
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Post by canuck on Sept 11, 2023 21:52:41 GMT
Hi John, The Riley does indeed call up a 4 psi radiator cap. These cap pressures are intended to provide a higher operating temperature in case of mega hot weather. If we use a 50/50 glycol to water mix in the cooling system then the boil over temperature is 220 0 F? The math is 3 0 F per psi? So with the standard cap we will see a higher range to +12 0 F, or boil over at 232 0 F My MK1 Riley has a 4 psi cap and never had an issue. My MGB has a 10 psi cap and no problems. I can't speak to the larger coolant capacity in the Riley. FWIW I did make and install a sheet metal 'deflector' at the front and between the top of the radiator tank and the grille. My thinking is I wanted to direct the flow of air through the radiator and prevent flowing above it. I was thinking this also may reduce air pressure in the engine bay. No science to prove this out. Bruce
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