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MG MGB GT V8 Factory Originals Technical - Kenlowe fans!

After consulting Kenlowe i have ended up with dual cooling fans, a 10 inch and 8 inch. Had a look at fitting them today, the 8 inch has come with 4 extra clips to fit to the fan, but no clips with the 10 inch.


1. should there also be 4 clips with the 10 inch fan?
2. They will have to be offset horizontally to cover as much as possible of the surface area of the rad?
3. Has anyone used the plastic rods which go through the radiator fins? Does this cause any damage?
4. Does anyone have a picture of these fans fitted?
5. Is there a better way of fitting these fans?

GLG Lavis

I would not mount the fan directly to the radiator core. Over time the weight of the fan and bumps in the road will work a hole in the radiator.

For a cooling fan you should install a single 16 inch with about 3000 cfm of air flow. Mount the fan to the radiator frame or where the radiator attaches to the car. If you need to move the radiator forward to allow the fan to fit it's well worth it.

Ebay has several fans available

I installed a 2700 cfm fan a year ago and now have excellent cooling performance.

Jim Miller

There is a heat gradient across the radiator to overcome. Which means any air you blow at the radiator will effectivly want to go around, not through. The fans should be close coupled to the radiator with some sort of ducting/surround so that the cool air has no chance of not going through. Most modern electric fans have this plastic surround intrinsic to the construction. I have one very large electric fan behind the radiator pulling air through. I am thinking of changing to two fans, one on the top LHS and front of the radiator and the other on the bottom RHS and back of the radiator. This will ensure best coverage with minimal interference with engine parts water pump etc. The reason why I'm thinking of doing this is that although the large fan works very well, it is quite noisy and there is no redundancy, if it breaks down I'm sunk. Also you can buy two stage thermostats (one of the VW's had them) .One for each fan.
I personaly don't like the "through the core" bolting approach. Brass or alumminium is very soft. If you do take this approach (many do) then make sure that you use a thick plastic surround for the bolts so that their much harder metal doesn't rub a hole in the pressure part of the radiator core. Perhaps cut a long bit off a polyethyene cutting board and drill a hole though?
Much better (I think) is to attach a couple of horrizontal lengths of thin formed aluminium across the radiator and mount the fans on those. My radiator has sides on it that would take a rivet.

PS make sure that the fan is turning in the right direction!. You can wire them to either suck or blow depending on which way you connect the two wires.

Some suck some blow if you run a fan backwards it looses a lot of efficiency. Most fan blades are cambered like a propeller and don't work well going backwards. I have one on the front left blowing and one on the back right sucking to cool my Mazda rotary MGA. Remember a fan sets the flow of the air so one running backwards could actually limit flow and cause overheating. Sorry Peter you can make a fan go backwards but you don't want to.
The nylon tie through straps are used all the time for fans and transmission coolers. Mounted with a foam pad front and rear I have never seen any wear through.
If your radiator is cross flow mount one up in a corner and the other down in the opposite corner so they will cool different tubes. If the radiator is down flow just mounting left and right is fine.
Jim have you ever seen a hole worn in a radiator or are you speculating? I agree it looks like it could but my experience says that it really isn't a problem. I am looking for negative feedback if you have it.
R J Brown

Thanks Guys
I am a bit more confident on fitting the fans now,I have spoken to Kenlowe and they are sending me another 8 inch fan as the 10/8 configuration means that a lot of the fans are over the edge of the radiator which is not to good.

If i feel that the fans can move (which they shouldn't with the foam pads) i will make a support bracket.

Once again Thanks.

GLG Lavis

And of course unfasten the spring clip and turn the blades over, if you don't want to be a sucker!. A good quality fan will let you do this.

As a follow on to this, i am not what you would call electrically minded, What sort of relay would i need to fit with these fans?, and i take it that i fit it between the fans and fuse box?

GLG Lavis

Any off the shelf, local autoshop/Kmart 12V positive relay will do. The fans usually come with one.
The control (switching on/off) two wires of the relay go one to ignition, the other to the (electric) thermostat. When the thermostat gets hot enought it becomes an earth & the relay operates. I'm using the air con' thermostat (92degC) that goes on the RR mechanical thermostat housing.
The other two wires go; one to the power supply and one to the fan. I have put a fuse between the relay and the power supply. I used a 30AMP fuse.
Do take care to use high amperage connectors for the fan wire conection. I got a packet of these high amperage connectors for $4 from Target, there are the "single twist the wires together and clamp with a screw" variety. Initially I tried to use a couple of crimp style bullet connectors, which got so hot they melted the insulation.

Rather than using a fuse, use a circuit breaker. If you blow a fuse, you are funbling around, trying to get out of 4 lanes of parking lot that was supposed to be a freeway to a shoulder before you overheat.

A circuit breaker will re-set in a minute or so.

Refer this to Dan Masters for comments.
Jim stuart

I mounted my fans (2 - 8") to aluminum bars and then mounted the bars to the edge of the radiator. I drilled holes in the side rails and tapped the holes and mounted fine tread screws to hold the fans in place with locktite.

I had to mount the fans on the front of the radiator in a pusher configuration as I did not have clearance behind the radiator.

I have a picture I can send you if you would like to see how they are mounted.

Jeff Howell
63B 215

Jeff Howell

For awhile in my former career I was responsible for electrical circuit protection for an automotive OEM that used literally hundreds of thousands of circuit breakers per year, (specifically: Volvo Truck's US division) so I know entirely too much about 12V circuit breakers that plug into fuse blocks in lieu of regular fuses.

Circuit breakers are very, very popular on tractor trailers and have been for years. Most truck OEM's still offer them as a factory option. You probably won't have any problem finding them at any truck stop or (preferably) heavy truck dealer's parts counter. If you must use breakers, I prefer Fasco brand. (I wouldn't touch a third-world import breaker with a ten foot pole.)

But should you use them? I have to honestly say I wouldn't recommend it. If you do use them, you should make sure to buy the right kind.

Please let me volunteer some background information. This is important stuff. If your circuit protection system fails your car could burn to the ground.

Automotive circuit breakers come in three basic types. All automotive circuit breakers should be labeled (on the breaker) with both type and current rating.

"SAE Type 1" are fully "automatic". They work a little like a thermostat switch. A conductive bi-metallic strip heats up when there's too much current. When it gets hot, it warps in such a way as to break the connection. Then it cools down, and automatically resets. Obviously, if there's a short circuit, it will cycle over-and-over-and-over. Depending on the circuit and failure, it may cycle quite quickly.

Please accept this advice: NEVER use an SAE Type 1 circuit breaker on any vehicle you care about. Reputable OEM's refuse to install them, period. They have several bad failure modes. One if the most common failure modes is that the contacts tend to weld together, at which point you no longer have circuit protection, and your wiring may burn-up with catastrophic results. This happens much more often than you might think - it's been the doom of many nice tractor trailers. (There are lawyers who've made their living from this issue.) Some brands of type-1 breaker exhibit other mechanical failures with disturbing frequency.

Type-1 breakers are dirt cheap.

"SAE Type 2" circuit breakers are called "remote reset" or "modified reset" in the trade. Type 2 breakers are opened by over-current and then remain open as long as the power is "on" or until the load is removed. How do they do this? They utilize resistance wire wrapped around the bi-metallic element and wired in parallel with the element. When the circuit breaker trips, the resistance wire heats up and keeps the breaker in an open position. Think of them as "semi-automatic". Your fan will stay off until you turn the ignition switch off for a moment, and then back on. (If your fan is only wired through a thermostatic switch, you'll have to wait for the engine to cool down, or you could disconnect the battery...) Anyway, if the resistance wire itself fails, the breaker becomes a de facto type-1 breaker.

Type-2 breakers aren't much more expensive than type-1 breakers, and IMHO they're much safer.

"SAE Type 3" circuit breakers are "manual reset". They usually have a little push-button right on them. They come in many brands, some are much, much more reliable than others... but all of them are also much more expensive and mechanically complicated than type-2 breakers, so they aren't anywhere near as popular as they once were. Most of the heavy truck OEM's removed manual breakers from their product offering when they began offering type-2 breakers.

Now for the kicker. The circuit-protection performance of commercially available breakers is orders of magnitude less consistent than fuses. They are ALL less reliable and predictable than fuses. If you aren't sure what to use, I recommend using a fuse. If you must use a breaker, your best choice is probably a type-2.

I'm going to stop here. Another time I'll climb back on my high horse and preach about fuses and/or relays.

Nutshell version: Glass fuses aren't good. "Blade" fuses are better. NO automotive electrical part should EVER be purchased from Walmart or Target. (Ever heard of Chinese counterfeit parts?) There are huge quality differences between brands of relays. (Bosch and Omron are better.) Sometimes you really do get more when you pay more.


Very enlightening, thankyou. I think i will probably start with a fuse and see if it blows a lot, but i will keep my hand near to the battery breaker switch for a while.

GLG Lavis

You obviously know what you are talking(typing) about and I never miss a chance of learning something new. Why are blade better than glass?. I stayed with glass because you can see the fuse which (sometimes) helps. Is it worth replacing my fuse box with blade type?

Hi Peter,

I knew I'd put my foot in my mouth! I'd prefer to give you a well-written answer on the "glass versus blade" question... but that kind of answer takes time to write. Watch the British V8 newsletter (it's free at !!!) and I'll try to put an article together on 12V wiring and circuit protection for an upcoming issue. Maybe I can recruit help, since I have rather narrow experience wiring actual British cars (just mine!), and zero experience with available wiring kits.

In the meantime, I'll direct you here: for a good introduction to "fuseology".

A few quick comments about this article:
1. blade fuses come in more different amperage ratings over a wider amperage range, so designers can better tune them to circuit requirements. The definite trend in automotive wiring has been to divide circuit protection over more and more circuits/fuses and to tier the protection as the article describes under the heading "3. Selective Coordination." Frankly, this is probably the biggest single reason why someone might want to replace the original MGB fuseblock.
2. in section IV the article talks about how a poor connection at fuse terminals effects fuse performance. This implies another reason to replace a 35 year old fuse block...
3. Section V talks about the importance of tight process control in manufacturing and particularly the skiving process... blade fuses are a newer technology and associated manufacturing processes are better controlled by design.
4. Section VII doesn't help answer your questions, but I think it's very interesting. On the Maximum Recommended Continuous Current graph you'll see that wire insulation derates dramatically differently depending on composition. The back-story here is that most automotive-spec wire you can easily purchase is PVC insulated. PVC isn't "bad"... it's what MG and most other car manufacturers use, but it falls into the "GPT" category. This chart makes the case for cross-link insulation as an upgrade, particularly if the wiring will be exposed to higher temperatures (like in the engine compartment!) Cross-link insulation is used on the wiring for pretty much all American-made heavy duty trucks. (There are other variables to consider: cost, ease of marking, abrasion resistance, fuel/solvent resistance, etc.)

About replacing your original fuse block... it depends on skill, budget, time, and tools available. To get the full benefit you have to change the schematic and harness, which takes some significant design work (by someone... like Dan Masters.) I can only say that generally I prefer newer technologies if it's feasible to implement them. That said, my own wiring isn't exactly state-of-the-art.

I hope that helps!

This thread was discussed between 29/05/2006 and 09/06/2006

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