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Home-made ducting for BJ8 radiator?


Jedi Hopeful
I know several of you have made additional sheet metal ducting to keep the air into the radiator, question is did anyone do it and have templates of the pieces they fabricated? I would like to do this and can fabricate them as needed, just thought it might be faster to use ones already in the works on your car.


Jedi Knight
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Sorry Ed no template or design only photos
on my restoration I make a copy of the rally cars with some modification to host the oil radiator- I have eliminated the lateral erars

on the chassis during the rebuild I have welded a bracket for stiffness ( a very right intuition) and to support the Oil Rad- then utilized to support alsothe aluminium
From a cardboard mask based on Photos of the original rally duct I have cut the aluminium -- lateral holes aren't necessary if you avoid the lateral ears
Added a separation to maximize the air flow to the Oil radiator and reinforce the lateral face of aluminim - rivets are the better way to connect the pieces- i have utilized bolts for modification during the continuos test make to controll the interference with the front body, Added also two extension forward the lateral upper face
Added a aluminum pipe from the extremity of the lateral faces for stifnes and avoid vibration --Undesidered Hole was closed with aluminium adesive ribbon
I have maintained only the holes for oil radiator pipes
Added two air flow holes to the front body for correct air flow at Oil Radiator
The road test demonstrated the utility and efficiency added to the cooling of the car - also the interior cooling was increased from the separation BUT
heat in the summer days is still present as USUAL in AH


Jedi Warrior
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Here is my design, wangdango. I made part of it removable to allow access to the crank dog nut for turning the engine for valve adjustment.


  • Radiator Shroud.jpg
    Radiator Shroud.jpg
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Jedi Hopeful
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For clarification, you want to put additional ducting in front of the radiator to direct the air? or on the rear of the radiator (i.e. shroud) to enhance flow? or to keep the air from recycling during idle?


Jedi Hopeful
I am open to all. Realize the original design is ok, but not great, I would like to get more air flowing thru the grill and into the radiator.


Jedi Knight
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I agree wit Geoffrey Healey, Engine cooling conclusions and to explain my project beginning and conclusion
for avoid overheating problems at my AH in the Italian Summer sunny days

The original FAN was completely inadeguate and also dangerous to the air flush circulation
the first step to avoid HEAT was the acquisition of TEXAS plastic FAN , improved flush air, are incomparable to the oldest

I considered the internal front body of the AH , and the air flush at speed and a moderate speed

at stationary, or moderate speed, radiator flush friction are nearest to a brick wall with oldest fan -with Texas fan are again insufficient to cooling the engine completely- consideration are that this are the more recurring situation on the city traffic, the probability of engine cooling turn to critical in this situation are nearest to 80%

at medium and high speed the flush through the radiator are better and cooling is adeguate to the engine heat
BUT it can be increased
1) adding more surface to the radiator OR better installing the OIL Radiator (remember that air cooled, and water engines are il large part cooled by the oil (in my 911 13 Liters of oil in circulation ) NOTE: this require ALSO a THERMOSTATIC valve for controlled temperature
2) a Front ducting are one of the better step to increase the air pressure and efficiency of the FAN
3) FAN Ducting increase the efficiency of fan, and flush in the engine bay
4) one Electric fan pushing air from front radiator to the rear engine fan -can help in extreme heat condition slow traffic or queue better with a Thermostatic control
https://photos.app.goo.gl/ce5raV24VTw0w3oO2 NOTE the Duct also on oil radiator -for air flush optim.
5) No forget to control the water gauge reliability controlling it by a digital thermometer
Applying all to your AH and never you have overheat problems in summer or Stelvio high drop climb road, or evacuation queue

(Actually I haven't applied to my AH the 3 step- waiting to find a stainless ribbon -to make a compete circumference duct around the fan)

Consider also where the car is destined to circulation in Alaska have others problems than the cars in circulation in Texas or Italy

On my MG TD and TC shifting from the original Steel Fan to a six or seven blade Plastic Fan (MG B) solved permanently the overheat problems


Jedi Hopeful
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So, what are the details on your cooling system? You say you have an upgraded radiator, what number of rows of tubes, and how many tubes per row? serpentine fins, or flat finned and are they louvered? How deep is the radiator? What fan are you using, and do you have a shroud around it? I assume you are using original air deflectors in front of the radiator? anything below or above the radiator like aluminum sheet metal? Does it cool okay on a warm day at speed, but when in traffic it will heat up?

On my BJ8, it cools well when at speed even on warm days it won't get above 180 unless I have to slow down or stop. Then it will get up to 212 or so if I don't rev the motor up to increase water flow, air flow through the radiator and over the engine, and improve oil circulation. I can maintain 200F on a warm day if the engine is reved to 1500rpm or so. I have a 5 row copper radiator, flat louvered fins, 160 thermostat, flex a lite plastic 14 inch fan, and kilmartin shroud. The air coming in below the radiator is also blocked by an A/C condenser (it doesn't feed the air into the radiator for obvious reasons). I have measured air temp into the radiator at idle in the garage, and it does get up to 100F due to side infiltration/recirculation which is common with these cars apparently. I did make some custom aluminum sheetmetal to block the side infiltration, but have removed it due to aesthetic reasons since the new radiator seems to be adequate in my case (I live in Oregon).



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I know several of you have made additional sheet metal ducting to keep the air into the radiator, question is did anyone do it and have templates of the pieces they fabricated? I would like to do this and can fabricate them as needed, just thought it might be faster to use ones already in the works on your car.

I've assembled a lot of separate air control pieces on my car. They seem to work, as I made the Healey Week trip with the coolant temp never getting above 180 ish. Also the "cold air" input is no worse than ambient air temp if you prevent hot air from the exhaust pipes from circulating forward to the cool air intake.

See: https://www.pbase.com/stevegerow/healeyaircontrol

For me this was a "craft" project: I made pieces of cardboard then aluminum. The first iteration sometimes separate pieces scotch taped together to fit an opening, then use that to make a single piece of cardboard, then use that as a pattern for the aluminum piece. When you mount the aluminum, you may have to modify it further -- it's an "iterative" process.

If I was doing another car, I'd try to make a bulkhead on either side of the radiator and conforming to the curvature of the bonnet as the easiest way to separate the area in front of the radiator from the engine compartment.

Look at a '55 Chevy in a car show and you'll see a wall where the only opening is through the radiator. That would be desirable for our cars.

PS - I originally tried to save templates but there were too many versions to get it right.


Jedi Hopeful
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I think it depends on what you're trying to achieve. If your car only heats up when it's standing in traffic, which seems the most likely problem, then I think you have a circulation problem around the rad. I had the "standing in traffic" problem. I concluded that fitting a larger fan just pressurises the engine compartment and makes the air circulate around the rad faster. I adopted Steve's method and made card templates before cutting out sheet steel. Time consuming but not difficult. The result is not pretty and they "fit where they touch", but it seems to do the job although I haven't yet experienced a really hot day yet to see just how effective they are. Whereas I was getting temps of over 95C standing in traffic I rarely see over 90 now so I think it works. I've only boxed in 3 sides so far as the steering box side is a bit more of a challenge and I wanted to see if it worked before I went to any more trouble. I had the same problem with my 1954 MGTF. I fixed that by upgrading the rad. I have to say that I think that is the only way of really fixing this problem although I have talked to people who have electric fans fitted. I think the cost is about the same as upgrading the rad. It seems to me however that blocking the front of the rad with a fan is likely to lead to problems on the move, so I'm going to opt for upgrading the rad with another bank staggered so that the air doesn't pass straight through if I find I still have a problem. If you look in the archives there's an extensive post on this subject by 'shortsguy1' dated 26 May 2017. You'll find some images of my efforts to fix this problem amongst the posts.

Joe A

Freshman Member
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Tangential commentary . . .

I've owned my BJ8 since 1995, but have not used it as a daily driver having put about 6000 miles on it in 22 years. I plan on driving it a bit more now as I've put quite a lot of work into it the past couple of years.

According to the temp gauge, my car often exceeded 200 F and eventually I would turn on the electric fan located on the welded criss-cross member ahead of the radiator, installed by the previous owner, and I'd always be able to bring the temp down to 190-ish even on a hot summer day in New York. My car was missing the fan shroud and I have the standard four-blade metal fan mounted to the water pump.

Just recently I replaced the radiator with one I obtained from A-H Spares in the UK. This radiator is described as having 30% more cooling capacity in a package that looks just like the original, but without the manufacturer's plates. A fan shroud is attached to the radiator itself.

The original radiator was beat-up in appearance and there were some signs it may have begun to weep a bit. While I had the radiator out, I fell victim, as usual to "may as well syndrome." I figured I may as well replace the water pump, 180 thermostat, belt and hoses at the same time.

I've only about 50 miles on the car since changing out the radiator and here are a few related thoughts . . .

As anyone who has done it will know, it's a bit of a frustrating experience removing and reinstalling the radiator as clearances to various potentially interfering bits of metal are tight.

After placing it in and out twice for various reasons, I decided to remove the air director plates ahead of the radiator and cut them along the creases about mid-way fore and aft, removing the half that abuts the radiator and pre-drilling the portion that I put back with its bottom brace in place - with four potential mounting holes. I reckoned that I may as well bead-blast and repaint what I took out and put back in and treat the chassis areas that I could not normally see with the radiator in place. I have a habit of making a simple job turn into a major undertaking. ;-)

To the uninitiated, one would not visually miss the rear half of the air director plates. My intention is to fabricate a slightly adjustable extension using the original pieces I carefully cut off. This will facilitate pulling and replacing the radiator in future should it be necessary at some point.

Results, so far?

I ran the car at first for an hour in the driveway as I recharged the cooling system - ambient temperature 75 F, and the temperature never went above 190. This is without having replaced the missing portion of the air director nor using the electric fan.

On the road, my perception is that the car is running cooler as the gauge has not yet indicated above 195 F.

A-H spares ships the radiators with cardboard protecting the cooling fins. It's a good thing I left the cardboard in place until I was finished with the project or no doubt I'd have dinged the fins with either the fan blades or the air-director plates. I have saved and labeled the cardboard!

The A-H radiator was painted after construction and this unfortunately included the 6 internal threads of the captured mounting nuts. This is one reason I had to take the radiator back out after putting it in. I forget to check and clean out the threads. It is impossible to get the mounting bolts into painted internal threads. A 5/16 -24 tap did the trick and made reassembly more pleasant. (A-H Spares has indicated it may check and clean out the threads on future shipments as a service to future buyers.)

I'll like go ahead and fabricate the missing half of the air-director plates, but at the moment, it hardly seems necessary. I see no reason to add extra ducting, but then again, I do not live in a hot climate such as one would have in Texas or Florida.
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