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MG MGB Technical - pulley diameters

I'm back on the pulley diameter issues. I know the crank pulley diameter was changed, increased, for later engines. I'm told that this was done to increase alternater output at lower engine speeds, but did the water pump pulley diameter change? One would assume that there was no need to paddle water faster and therefore run the risk of the pump cavitating at high engine revs.
Allan Reeling

There were at least seven pump pulleys over the years, although that includes ones suitable for short-nose and long-nose pumps, double and triple grooves, and late North American and Japanese engines apparently having twin pulleys. If they wanted the alternator to run faster why didn't they just reduce the size of that? Although that would have resulted in a smaller radius in the belt which may not have been good for it.
PaulH Solihull

I give in then! I'll stick with the smaller crank pulley, with the alternater and water pump pulleys off the old engine. Which, as a combination, seem to work quite adequately at the speeds they run at. As for the solutions Leyland/BMC arrived at, to solve their mechanical and other problems, deeper mysteries I have yet to find! Was the need to boost charging, an attempt to cope with all that modern equipment installed on later models? Apart from better headlamps and a rear screen heater on the GT, what were they? But you have to love em!
Allan Reeling

"all that modern equipment installed on later models"

Eh? What were they indeed! The HRW was available from the GTs inception in 1965, and whilst the headlamps did increase from 60/45 to 75/50 that was for the 1970 model. It's always amused me that later cars got multiple fused ignition circuits and ignition relays (which incidentally used to stick on and needed most of the load taken off them and put back onto the ignition switch!), and even circuit breakers because the fuses were getting too hot, but the V8 GT with HRW and twin electric cooling fans had everything hanging off a single fuse! Mind you, I've added a relay to my HRW and uprated the cooling fan circuitry, which has resulted in significantly better performance from both of them.
PaulH Solihull

I know you guys are flirting with a national legacy, one which I've enjoyed for over 40 years now ( Sept 1970), but for me and my DD 77 MGB, the 105 amp alt conversion just made obvious sense...particularly since upgrading to a Hayden puller, halogen headlights, and a 200 watt amp for my aging ears. That spud puts out 50 amps at 1000 rpms, and when all- in, about 140% more than the pitiful Lucas, fully lit, at 35 amps. I sourced a Saturn alternator, rotated the front mount, saved one wire on the connector clip to the brown/yellow "ignition" light and hung the 2 brown wires on the rear screw post capping them with a rubber boot for protection. EZ peesy and away you go. Sounds like more fun than messing with pulley diameters to me. Hey, just my hedonistic, dastardly Yankee opinion, donchaknow. Cheers, VEM
vem myers

This thread was discussed between 17/11/2011 and 27/11/2011

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