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Oil pump differences - 3-main vs 5-main

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larrym Avatar
larrym Silver Member Larry M
near Sacramento, CA, USA   USA
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1963 MG MGB "Racer"
1968 Volkswagen 1600 "Manx"
OK - so why the differences & is either one better?

picture

looks to me that the later pump was simply cheaper to make - the inlet port does not match to anything on the block
(or did they use this later pump in some tractor that had a block inlet?)

.



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fast-MG.com Dave Headley
Cortez, 4 corners, Colorado, USA   USA
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Larry, compare the spindle gear extension length. The 5-main is longer and the block mounting surface is at a different depth. Both pumps draw oil in from the sump in the same way. The 3-main suction port is fully machined and you will find a plugged hole in the side. The 5-main pump replaces this plug by sealing off the die cast port against the block surface. Good question BTW.cool smiley

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Be Coming Kelvin Dodd
So. Calif., USA   USA
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Larry.

The 5 main pump is a bit longer because the extra main bearing was in the way of the machining for the pump.

The 5 main engine was designed to be more rigid for the Front Wheel Drive Austin/Morris 1800 application where the transmission was mated to the bottom of the block in a similar manner to the Mini/Austin 1100, 1300.

The Austin/Morris 1800 was available as an automatic and the extra port you see on the oil pump fed the transmission hydraulic system.

It's important to take a step back from the sports cars and understand that many upgrades and modifications were a result of the domestic saloon car program that really was the bread and butter.

Kelvin.

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fast-MG.com Dave Headley
Cortez, 4 corners, Colorado, USA   USA
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Kelvin????? The extra port on the 5-main pump is on the suction side so it couldn't be feeding oil.confused smiley

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