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MG TD TF 1500 - MGB Fan

Gentlemen, I have a bit of a conundrum that I could use some advice on! I have seen the results of an original fan blade breaking at speed and it was a mess. The chap has a TD in Tucson and he solved the problem by putting a weld bead along a new set of fan blades.
I elected to go for the seven bladed MGB plastic fan that per Dave B's , and others, should be fitted with the blade curve facing the engine; however this poses my TF configuration a problem in that it moves the blades close enough to the radiator so that the blades just clip the lip of the bottom tank. Thus that means I have to do something to solve the issue! The two most lickely solutions for me are 1) take 1/2" of the spacer via a lathe or 2) turn the fan around and mount it backwards, this moves the leading edge of the fans inwards away from the radiator by about an inch and would mean that I wouldn't need to have any machining done.
My question is, can anyone tell me the possible impact on cooling with the fan mounted backwards?
Thanks for the help!
Best regards
Rod Murray 54 TF
Rodney G Murray

As you would be trying to blow air forward through the radiator I think it would greatly reduces the effectiveness of your cooling system...
Geoffrey M Baker

I beg to differ. If you turn the fan around it still blows the same way. Maybe less efficient but still the same way. I tried it with a little desk fan and confirmed the results. Jud.
J. K. Chapin

Jud has it right. Rod, is there any chance that your motor mount is tired and your engine is sitting slightly low? I use the MGB fan in my TD and am delighted with the results TFs can be snug, but they're pretty. Bud
Bud Krueger

Well, I definitely differ. I've never heard of a fan that works in both directions. Every fan blade is designed to push air in one direction only. Reversing a fan blade pushesair the opposite way.
In the engine bay, the effect would be to negate incoming air through the radiator when driving, by pushing air in the opposite direction. I can only imagine that this will reduce cooling efficiency in all situations except when at rest, when the fan could successfully push air through the radiator and have some cooling effect - but still the opposite that was designed for.
We do talk about pusher and puller fans, but typically this is handled by putting a pusher fan in front of the radiator, thus pushing air through the radiator. A puller fan sits behind the radiator and pulls it through.
Geoffrey M Baker

The blade will still pull the air through the Rad Geoffrey. It Does have a slight arc in the blade but it's pretty marginal. Many people think if you turn the fan over it will send the air in the opposite direction.....not true...if you turn one over it still has the same pitch as it did in the other direction. Sometimes the logic of the mind will play tricks on you. Don't believe me? Just take a fan and do the test yourself.

The B fan on a TF is very tight...very tight. Maybe it will fit in the reverse position as it would be normally mounted on the TD. The only way to know is to have a go at it. I did mount the one on the TD I had here that way first but I found that the blades would just touch the upper radiator hose so I had to turn it around.
MG LaVerne

Think airplanes. Motor in front and the fan (aka propeller) pulls air from the front and pushes it to the rear. Turn that motor around and stick it in the tail. You've turned the fan around but you've also reversed the rotation of the motor shaft. The fan pulls air from the tail and pushes it forward - she won't fly. To use that motor in the rear you need a fan (propeller) with reversed pitch blades. So...

Turning the propeller around while leaving the motor mounted in the front (same shaft rotation direction) still pulls air from the front and pushes it back, maybe just not as efficiently. Jud
J. K. Chapin

Geoffrey;
See attached drawing.

I drew and approximate fan blade.
I rotated it twice. I did not flip it.

I think you can see that if it rotates in the same direction the air flow is the same.

Jim B.

Jim B in NJ

OK I'll buy it. :)
The fact that the blades do have a curve means there is some loss in performance, though...
Geoffrey M Baker

Geof,
I took the spacer to a machine shop and had it shaved...fan fit fine & Bob's your uncle!
Bob Dougherty

I elected to put the fan in backwards as I found that the spacer is a casting and to cut the 1/2",off, that I would like for flexing blade potential, means that I would be cutting into the center of the casting void Thus what I will do is accept the degraded fan performance ( although performance of 7 inefficient blades shouldn't be to far off the 4 bladed original). Later when the car is done I'll make a new thinner spacer out of aluminum.
I do like the look of the MGB 6 blade fan, has anyone modified one for use on "T"'s? It looks much sturdier than the 7 blade, and doesn't seem to protrude forward as much!
Best regards
Rod 54 TF
Rodney G Murray

I'm puzzled (not unusual). Perhaps it's one of these TF issues that I get into trouble over. The MGB 7 blade fan that I have on Lazarus (my TD) was given to me by Jim Merz. I've done nothing to the fan Distance Piece, some call the spacer, to have a solidly mounted fan. I think Jim changed the washers in the mounting holes of the fan. I don't understand what all this hullabaloo is about. What am I missing? Bud
Bud Krueger

I've got an extra 6 blade steel MGB fan Rod. I looked at it as a possibility but the mounting holes are not anywhere close.


Fan sits closer to the rad in the TF as compared to the TD...at least in the two examples I had here Bud.

MG LaVerne

another view

MG LaVerne

I have a new MGB plastic fan to switch out my stock steel X blades as I don't want a catastrophic failure to occur. I didn't realize these were not a direct replacement. Does any have a source or spares of the bushings to take up the bolt size difference for a XPAG configuration. What did you use ?

Bill Chasser Jr
TD4834
W. A. Chasser Jr

Bill,
The holes in the MGB 7 Blade fan are not uniform in size due to the pressing but average 6.95mm in diameter.
The best way to do it is to ream them to 7H7mm and using 7mm brass stock make ferules/sleeves which are 6.65mm long and drill a 5.2 ... 5.3mm hole using a lathe.
Regards
Declan


D Burns

Reversing the fan will severely reduce its efficiency to the point that air will barely blow. It MUST be mounted in the correct orientation or it will do little good at all. Run a desk fan in reverse and see. You can barely feel any air movement.

An alternative to the MGB fan is a metal flex fan. No clearance issues and a modern, more efficient blade design. Neither one will look period correct though.
Steve Simmons

Installing an MGB fan or any modern designed fan blade should increase efficiency and thus cooling. However, it won't save you from "catastrophic failure".
If you are getting high temperature readings and have a functioning water pump and a decent radiator, I strongly suggest you start by looking at the heart of the problem... gunk buildup in the water passages of your engine.
Mine was so severely occluded that it led to engine failure with a melted center camshaft bearing.
If you have not had your engine checked, and have high temp readings, it's time to do so.
I had to have my block boiled TWICE before I felt it was clean enough (and I spent hours with brushes and rods checking every hole). I paid particular attention to cleaning out the hole where the engine drain tap fits, that was completely blocked with oily residue and junk that the boiling did not get out.
Then I did the mod listed on the board of drilling an extra hole.
Then I took a long neck die grinder and improved the entrance and exit areas of the engine passages, removing rough stock and smoothing the metal.
I now have an engine that, with a functioning radiator and water pump, should operate at factory spec or better - and last another 60 years.
Seriously, if you haven't addressed this problem, any cooling improvement - improved impellers, new water pumps, rebuilt radiators, better fans - are nothing more than a Bandaid slapped onto a much, much bigger problem.
Sorry to harp on the subject, but I too was planning various cooling modifications to handle my cooling problem - until the engine failed. I was very lucky in that (because I was driving at 1/2 mph) the overheating that melted the camshaft bearing did not proceed to melt the main bearings, and result in broken crankshaft, conrods, camshaft, pistons and more...
Geoffrey M Baker

Thanks Declan for the specs re the bushings. Do you have any of these made up. Machining cost are astronomical here in Ca.?

Geoffrey my comment re catastrophic failure was in relation to an exploding fan blade due to fatigue not a cooling issue. But your comment is well taken and discussed at length in other recent threads

Cheers

Bill Chasser jr
TD4834



W. A. Chasser Jr

Geoff, it's a shame that that catastrophic failure happened to you. I'd be willing to bet that, by far, the majority of owner's cars have had their engines hot-tanked before a rebuild. It's a shame that yours never received that process. Was your engine never rebuilt by a reliable shop? Bud
Bud Krueger

Bud, we don't know. My father thought that the car had low mileage. He had never had any engine work done, and thought that the previous owner, a good friend of his, had never had it done, either. However, as I started to work through the car, I had my suspicions. Firstly, it had had a complete paint job. Secondly, the engine was painted a non-original color.
When the engine seized, we took it apart and found that while crank and cam were standard, pistons were +.040 which means it definitely had engine work done at some time. The head has been somewhat "ported" as well.
So clearly, the engine was taken out at some time (otherwise it would likely not have been painted, had the work been done leaving the engine in place.) If they took it out, did they hot tank it? Maybe. If we assume the engine work was done before either my dad or his friend owned it, that would take it back to the early seventies or sixties. I suppose with the right conditions, the block could fill up with solid gunk in the 40 years since....
Flip a coin. Maybe, maybe not.

Geoffrey M Baker

When I pulled the engine of 'the53' apart it was full of crud. It had sat for about 35 years, shortly after having been completely rebuilt. (Except for tightening ALL of the wrist pin bolts.) After hot-tanking it still took a lot of brushwork. Bud
Bud Krueger

Although Declans' solution is perfect, I think my solution is perfectly adequate; I used some plastic tubing to make spacers.
Looks messy but works a charm!

Willem van der Veer

When I installed my MGB fan, I had the same idea as Willem v d Veer but used metal bushings with OD that fit nicely into the plastic and the ID matched the original TD fan bolts. But, I considered that the fan may be able to somehow come loose from both the bushings and the small head on the bolts. So, I added oversize metal washers to each bolt so as to hold the fan, bolts and bushings in place. Just my way of overkill maybe but I'd rather be safe than sorry.

Jim Merz

W. A. Chasser Jr, California, USA
Thanks Declan for the specs re the bushings. Do you have any of these made up. Machining cost are astronomical here in Ca.?

Geoffrey my comment re catastrophic failure was in relation to an exploding fan blade due to fatigue not a cooling issue. But your comment is well taken and discussed at length in other recent threads

Cheers

Bill Chasser jr
TD4834




Bill,
I'm afraid I don't have any ready made up.

Regards
Declan
D Burns

This thread was discussed between 29/08/2015 and 05/09/2015

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