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MG MGB Technical - 67 Fan 3 blade vs 6 blade?

Is the use of the 6 blade metal fan used after 67 instead of the standard 3 blade a good idea and easy to mount up? My BGT is getting put back together and I have both fans here. I recall they both mount to the same water pump but I does the early pully work?
R Stegs

Works just super. I have a 67 GT that has the 6 blade metal fan. It is a perfect replacement for the three fan.

Never ran the car with the three blade, but it made the trip to Gattlinberg TN from Wisconsin without the temp gauge going above 90.
Bruce-C

The fan butts up against the pulley, and clamps it against the pump flange, so whatever fan you use doesn't change the pulley. All you have to think about is the hole spacing, and also the offset of the blades. Some fans need a spacer between the fan and pulley, and consequently longer bolts, or the blades hit the engine. They can be fitted the other way round which misses the engine, and in fact puts the blades very close to the standard distance from the radiator, but the blades are rotating the wrong way which reduces efficiency slightly. There are also long-nose pumps with a deeper pulley and these don't need the spacer or longer bolts. 6-blade metal should be a straight swap for a 3-blade metal, but do make sure it is the right way round and spacing to engine and radiator is correct.

This page http://www.mgb-stuff.org.uk/cf.htm shows a set of photos of 3 and 6 blade fans with and without spacers.
Paul Hunt

I,too,have a'67B and ran the 3 blade for 20 years. When I had access to a 6 blade I did the swap with no problems. It may be psychological but I think that it cools a bit better. RAY
RAY

It certainly should do, at the expense of more noise (Germany and Switzerland had to revert to the 3-blade for this reason) and some loss of power. A friend changed his UK 72 from 3 to 6 prior to a tour of Portugal (pretty hot) and had no problems at all. Since coming back to the UK it seems to be overcooling according to the gauge, even though in theory the thermostat should compensate for that.
Paul Hunt

Better still is to fit the 7 blade plastic fan - same issues over clearance but even more efficient & quieter.
Chris at Octarine Services

Hi Chris

I was under the impression that the plastic fans would not fit on the early B. What parts are needed for this?
Bruce-C

The MGA 6 blade steel fan will fit the 3 BRG MGB water pump & the % BRG pumpup to the 18GG motor. If you want to fit the 6 blade fan to the 5 BRG it will bolt straight on. Howerver the best bet for the 5 BRG 18GB/GD/GG you are best to fit the short water pump GWP130 & the 7 blade plastic fan. My 67 GT has always overheated in slow stop/start traffic or slow climbs up hill in traffic. The only way to stop it getting hot is to keep the revs over 1500 in traffic as the 3 blade fan does not suck enough air at low revs. It is all OK in winter.
I have a 70 Rdstr with the same pump. If I fit the GT rad to the 70 B it is all OK but the 70 B rad in the 67 overheates. Conclusion - the 70 B has a recessed grille and therefore gets better air flow.
Garth Bagnall

I considered switching to the 6-blade fan when I added air conditioning to my '67 GT, thinking that the 6-blade fan might cool better. I finally decided to continue using the 3-blade fan because it allows easier access to the front of the engine. This is especially helpful when I need to adjust the fanbelt-tensioning pulley near the bottom of the engine.

The 3-blade fan has continued to do an adequate job except when idling on very hot days. But I have an auxiliary electric fan to use then. I don't believe a 6-blade fan offers any advantage when the car is moving, as the breeze created by the car's motion will quickly outpace the cooling ability of any belt-driven fan. -G.
Glenn G

I considered switching to the 6-blade fan when I added air conditioning to my '67 GT, thinking that the 6-blade fan might cool better. I finally decided to continue using the 3-blade fan because it allows easier access to the front of the engine. This is especially helpful when I need to adjust the fanbelt-tensioning pulley near the bottom of the engine.

The 3-blade fan has continued to do an adequate job except when idling on very hot days. But I have an auxiliary electric fan to use then. I don't believe a 6-blade fan offers any advantage when the car is moving, as the breeze created by the car's motion will quickly outpace the cooling ability of any belt-driven fan. -G.
Glenn G

This thread was discussed between 17/09/2008 and 03/10/2008

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