• Hi Guest!
    If you appreciate British Car Forum and our 25 years of supporting British car enthusiasts with technical and anicdotal information, collected from our thousands of great members, please support us with a low-cost subscription. You can become a supporting member for less than the dues of most car clubs.
    There are some perks with a member upgrade!
    **Upgrade Now**
    (PS: Subscribers don't see this gawd-aweful banner
Tips
Tips

How far is your mechanical fan from the rear of your radiator?

Share this page

mikephillips said:
I recall reading an article on this issue where it was mentioned that when there isn't a full shroud the fan needs to be within an inch or so of the radiator. When it starts getting further away there is a tendency to draw air from the sides of the fan which then reduces what it will draw through the radiator since the air seems to flow easier from the sides since there's no restrictions. And since that flow from the sides isn't passing through the radiator, it's not capturing any heat from the coolant. With a full shroud it can be further back as long as it isn't outside the shroud.
Click to expand...

Hi Mike! Those were my exact thoughts. Unfortunately, there's no way to get the fan within an inch of the radiator core, so the effectiveness of the shroud is crucial.

jlaird said:
the cardboard stuff was not on a bugeye but a later model mg maybe a MGB even. Glad the shroud helped.

Oh, I assume you have the shroud that goes around the sides and over the top of the radiator and is attached to the radiator??

Just something you said, I bet it is missing.
Click to expand...

Hi Jack! That would have explained my cooling problems for sure, but I do have a shroud on my radiator that covers the top and about 2/3rds the way down on both sides. It's the open space below the shroud that concerns me. Maybe I should go find an MGB to look at and see how the cardboard was used.

Dan
 
DanLewis said:
Maybe I should go find an MGB to look at and see how the cardboard was used.
Click to expand...

No cardboard shroud on an MGB. Triumph TR3-4 had one in FRONT of the radiator to channel air from the grill to the radiator. MGB had a panel that the radiator sat in to keep air from flowing around it -- there was, however, no shroud around the mechanical fan.

Bugeye just has that metal shroud on the top and sides of the radiator.

Your fan is on correctly, and not backwards, right?
 
Hi Drew,

drooartz said:
No cardboard shroud on an MGB. Triumph TR3-4 had one in FRONT of the radiator to channel air from the grill to the radiator. MGB had a panel that the radiator sat in to keep air from flowing around it -- there was, however, no shroud around the mechanical fan.
Click to expand...

Thanks for the info!

Your fan is on correctly, and not backwards, right?
Click to expand...

Yes. And is pulling air through the radiator, but not much at idle - only barely perceptible.

Dan
 
At speeds of around 35 and up you don't need a fan. Natural air flow should be enough. At speeds around town all the British cars I have encountered needed a better shroud so I think your mods would be helpful. I have made shroud's before by just cutting a round hole for the fan out of sheet metal and then bending down the sides so that one end's up with a shallow box. Seems that something similar could be made up to fit inside the side shield's on the BE radiator quite easily.

Kurt.
 
Hi Kurt,

nomad said:
At speeds of around 35 and up you don't need a fan. Natural air flow should be enough. At speeds around town all the British cars I have encountered needed a better shroud so I think your mods would be helpful. I have made shroud's before by just cutting a round hole for the fan out of sheet metal and then bending down the sides so that one end's up with a shallow box. Seems that something similar could be made up to fit inside the side shield's on the BE radiator quite easily.
Click to expand...

Certainly the Bugeye needs a better shroud! :smile: But of course the problem is that the only way to install the radiator requires lowering it down over the fan. Since the shroud is attached to the radiator, then it has to have an opening at the bottom to clear the fan when the radiator is installed. That tells me that an effective shroud that surrounds all of the fan has to be in two pieces - the existing one that covers the top and most of the sides, and a second piece (that's missing in a Bugeye) that covers the bottom and the rest of the sides.

Thanks!
Dan
 
Dan, I was thinking more like build the box like I described to fit inside the existing shroud. Fit it over the fan and then lower the radiator down on to it and screw it to the existing shroud. Of course I don't have the situation right in front of me so I may be all wet with that suggestion!

Kurt
 
Hi Kurt,

nomad said:
Dan, I was thinking more like build the box like I described to fit inside the existing shroud. Fit it over the fan and then lower the radiator down on to it and screw it to the existing shroud. Of course I don't have the situation right in front of me so I may be all wet with that suggestion!
Click to expand...

I'm not sure there's enough clearance between the fan and the top of the existing shroud to do that, and it would probably be pretty difficult to screw it to the existing shroud once the radiator was in place. I'd rather find a way to attach the extra shrouding to the frame so that I can still simply lower the radiator into place and have the top and bottom halves of the shrouding meet.

I think my next step will be to use the sheet metal piece that I made and attached to the cross member as an initial template for a larger piece that extends upward on each side to block the remaining open areas. I'm still not feeling much airflow through the radiator at idle, so I don't think the shroud (even with my initial mod) is as effective as it could be.

Dan
 
WOW! I just fabricated a shroud extension for the bottom, rear and sides of my radiator and got a huge increase in airflow through the radiator at idle! I haven't had a chance to test it on the road yet, and it's not all that hot here today anyway, but I'm confident it will make a big difference in helping to keep the engine temperature from climbing at idle. Pictures below. It's held in place by three sheet metal screws that are screwed into three small holes drilled into the top of the cross member, just behind the steering rack. The sides of the extension go on the outside of the radiator, and I then used a little duct tape to tape those sides to the sides of the existing radiator shroud. As you can see, the area below the fan is now blocked as well. You might also notice that the fan is offset to the left relative to the shroud; that's because the existing radiator is also offset relative to the fan (or is it vice-versa?)

IMG_6531.jpg IMG_6533.JPG
 
I find all this most interesting, however. I just came in from the driveway where i let Miss Agatha idle for 20 min or so and the thermostat was rock steady at 180.

Now keep in mind this block was boiled twice during rebuild. Radiator was also professionally cleaned and is in like new condition.

What I am trying to say and not doing a good job of it is your engine and radiator is not to spec otherwise there would not be an overheating prob.

The only time I have ever had a bugeye overheat is when going over large mountains at speed, or trying to speed.

I think a shroud is an excellent solution to pulling an engine that is running just fine.
 
Hi Jack,

Interesting. I wish mine cooled as effectively as yours.

How hot was it outside when you let it idle? Tell me about your engine so we can compare: Are the displacement and compression ratio stock? Mine's a 1275 with 9:1 compression and a "street" cam. The block was boiled when it was rebuilt, and that was probably only about 3,000 miles ago and the radiator is essentially brand new. The cooling system is filled with water and one bottle of Water Wetter - no antifreeze (the Water Wetter provides the lubrication that would otherwise be provided by the antifreeze.)

Oh - One more thing: What kind of thermostat do you have? Is the bellows type or the more modern type? And do you use a blanking sleeve?

'Best,

Dan
 
BlueMax said:
Blanking sleeve would replace the thermostat wouldn't, not work in conjunction? :smile-new:
Click to expand...

My understanding is that if you don't have one of the older style "bellows" thermostats, then it's not blocking off the bypass when it comes up to temperature and thus doesn't direct as much water through the radiator. Using a blanking sleeve with a newer "pellet" style thermostat is supposed to be a fix.

See: https://www.britishcarforum.com/bobmuenchausen/12299.html

Dan
 
Last edited:
Think what I would do is order a correct thermostat from Moss and get rid of the blanking plate.
 
Engine is a 948 bored to 998 otherwise stock everything that counts.

Thermostat is what Moss sent. Yep about 50% anti-freeze. Will top out at about 6K, no balancing or porting or relieving or matching ports.

But had the second BE bored 30 over, alm three ring pistons. Road cam, balanced to 1/4 gram. Flywheel cut down, ported relieved, polished, matched. Carbs worked over as well. Would turn about 7500 before things started to float, came on cam about 4500 RPM, never overheated except when i was going over the mtns and pushing hard.
 
Well guess what, that is not what I have either then.

I do have page 18, item 9, 180 degree, price 4.95
 
Hi again, Jack! :smile:

jlaird said:
Engine is a 948 bored to 998 otherwise stock everything that counts.

Thermostat is what Moss sent. Yep about 50% anti-freeze. Will top out at about 6K, no balancing or porting or relieving or matching ports.

But had the second BE bored 30 over, alm three ring pistons. Road cam, balanced to 1/4 gram. Flywheel cut down, ported relieved, polished, matched. Carbs worked over as well. Would turn about 7500 before things started to float, came on cam about 4500 RPM, never overheated except when i was going over the mtns and pushing hard.
Click to expand...

That's a really nice rebuild! Before I put the 1275 in my Bugeye, I had a stock 948. It never overheated. The problem is that the radiator was designed for a 948, and a 1275 puts out quite a bit more heat.

Dan
 
Choice, put up with it or have another row of fins added to a bugeye top and bottom radiator. As i remember there are two in there and a core with three is available from a real radiator shop.

Or use an alum racing radiator from one of the likely sources.
 
Hi Jack,

Beginning to feel like old friends! :smile:

jlaird said:
Choice, put up with it or have another row of fins added to a bugeye top and bottom radiator. As i remember there are two in there and a core with three is available from a real radiator shop.
Click to expand...

I don't have a problem at speed when air is pushing itself through the radiator, only at idle. And now with better airflow through the radiator, I suspect the situation is much improved. Of course I won't know until the next hot day here. If not, then as you say, I may have to put up with it. :smile:

Or use an alum racing radiator from one of the likely sources.
Click to expand...

Well, actually that's kind of what I have. It's a two-row aluminum radiator. I say "kind of" because (and I know you won't like this) it's one of those Chinese one's from eBay. I will say, however, that it does a little better than the old stock radiator that I had before, even after it had been cleaned out by a radiator shop.

BTW, I saw in another post that you used to live in Atlanta. I grew up there until I got my BSEE from Ga Tech, then took a job in upstate New York. Left there in '75 when I got my PhD and have been in California ever since. I teach computer engineering at Santa Clara University. I haven't had my Bugeye nearly as far back as your history with them goes. I bought mine about two years ago. A friend of mine in high school (Briarcliff HS in NE Atlanta) had one as a senior (in 1964) and I had wanted one ever since. 'Just finally got around to buying one.

'Best,

Dan
 
Here is what i would suggest, along with your nice lower air diverter take the blanking plate out, leave the thermostat in. In my opinion the blanking plate is restricting the flow through the radiator and engine. Now, not that I have never been wrong but I have never heard of using one in conjunction with a thermostat. The blanking plate is really used to slow down the flow through the radiator so the fluid has time to cool, least that is how it was explained to me but this is also a function of the thermostat. Useing both at the same time is just plane overkill and not something I would do.
 
Back
Top