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

[DanLewis]

Like some others, I've had an engine cooling problem ever since I put the 1275 in my Bugeye. It's OK (read "marginal") when driving at speed, but if I idle in traffic on a warm (~75 degrees) day, the engine temp will climb. This is with a later model plastic fan, a brand new 2-row aluminum radiator, Water Wetter instead of antifreeze, wrapped headers, and timing set at 0 degrees at idle.

I tried replacing the mechanical fan with an electric fan, and although it brought the idle temp down, it raised the temp at speed - probably because it restricts the airflow. What I did notice, however, was that at idle with the electric fan on, the airflow through the radiator was MUCH greater than it had been with the mechanical fan. That got me thinking that maybe the problem was how far the mechanical fan was from the radiator core. I measured a full 3", which seems excessive for two reasons: (1) the fan shroud only covers the top half of the fan, thus pulling air from under the radiator instead of through it, and (2) I found the following statement on SummitRacing.com in the description of a fan spacer: "Belt-driven fans work best when they are 3/4 in. to 1 in. from the radiator's surface."

So I'm going to do two things: (1) add a bigger fan spacer between the water pump and the mechanical fan to move it from 3" away to 1" away, and (2) fabricate some sheet metal to try and close off some of the space below the fan that the fan shroud left open. When I'm all done, I'll report back, but just wondered if anyone else has ever thought about moving the fan closer to the radiator?

Dan

 

[smaceng]

Don't most people use a pusher fan and mount it in the bonnet?

 

[DanLewis]

Don't most people use a pusher fan and mount it in the bonnet?

When I installed an electric fan it cooled fine at idle, but restricted airflow and raised the engine temperature when driving at speed.

Dan

 

[Trevor Jessie]

On the 1275 Midgets with the crossflow the fan is certainly closer than 3 inches. Without looking I'd guess maybe less than an inch.

 

[BlueMax]

For more efficiency with cooling in a Bugeye use a puller fan mechanical or electric, there is about a 30% better cooling ability if fan is behind radiator. Always use the radiator shroud for street applications. A single row radiator will have greater capacity of coolant than a double row.


Also adding an oil cooler with no less than a 13 rows will add one quart of oil capacity which is like adding two to three quarts of water cooling ability.

 

[DanLewis]

BlueMax,

For more efficiency with cooling in a Bugeye use a puller fan mechanical or electric, there is about a 30% better cooling ability if fan is behind radiator. Always use the radiator shroud for street applications. A single row radiator will have greater capacity of coolant than a double row.

The electric fan I mentioned in the original post was a puller, and yes - it did cool very well at idle, but restricted airflow at speed, resulting in higher temps while driving.

Also adding an oil cooler with no less than a 13 rows will add one quart of oil capacity which is like adding two to three quarts of water cooling ability.

I have a 13 row oil cooler installed.

Dan

 

[DanLewis]

Trevor,

On the 1275 Midgets with the crossflow the fan is certainly closer than 3 inches. Without looking I'd guess maybe less than an inch.

Thanks for checking. That's more like what I would expect!

Dan

 

[BlueMax]

If you haven’t already installed high volume GWP-134 water pump with a 4.75” pump pulley, these can help too.

 

[DanLewis]

If you haven’t already installed high volume GWP-134 water pump with a 4.75” pump pulley, these can help too.

Where can I find the larger pump pulley?

Dan

 

[jlaird]

Seems that I remember a heavy card board stuff below the fan making up that part of a shroud. Might us something like that and duct tape to do a test thing.

Fan is preaty close on a bugeye, you can get a new fan belt through there but is close.

 

[DanLewis]

Hi Jack,

Seems that I remember a heavy card board stuff below the fan making up that part of a shroud. Might us something like that and duct tape to do a test thing.

'Never seen or heard of that before. Was that OE, or something someone added?

Fan is preaty close on a bugeye, you can get a new fan belt through there but is close.

Do you mean close to the radiator, or close to the shroud?

Thanks!

Dan

 

[BlueMax]

You will find it here!! https://www.minimania.com/part/CAM6408A/Water-Pump-Pulley---472---Cnc-Aluminum

Also you can find it here!! https://www.minispares.com/product/...search/classic/water pump.aspx|Back to search

HTH

 

[DanLewis]

You will find it here!! https://www.minimania.com/part/CAM6408A/Water-Pump-Pulley---472---Cnc-Aluminum

Also you can find it here!! https://www.minispares.com/product/...search/classic/water pump.aspx|Back to search

HTH

Thanks, but (correct me if I'm wrong here) doesn't slowing down the water pump only help at high rpms to prevent cavitation? At idle speed, I'm guessing that there's actually minimal water movement, and it's at idle that I have my overheating problem. In fact, isn't that the motivation for an electric water pump - to insure adequate water flow, even at low rpms?

Dan

 

[SaxMan]

I was under the hood of my '69 Sprite this evening. I didn't get an exact measurement, but it is less than an inch, probably closer to 3/4 of an inch. My water temperature climbs at idle on warm days, too. This particular motor runs unusually cool for a 1275 with the crossflow radiator. My temperature needle seldom passes the right of the "N" at idle, and usually once at speed, it plants itself halfway between "C" and "N".

 

[DanLewis]

Saxman,

I was under the hood of my '69 Sprite this evening. I didn't get an exact measurement, but it is less than an inch, probably closer to 3/4 of an inch. My water temperature climbs at idle on warm days, too. This particular motor runs unusually cool for a 1275 with the crossflow radiator. My temperature needle seldom passes the right of the "N" at idle, and usually once at speed, it plants itself halfway between "C" and "N".

Thanks for the feedback! That's the second person who has a later model Sprite (not the Bugeye) and said that the fan was within about an inch of the radiator. So the nagging question for me is what's the distance in other Bugeyes - i.e., is there something odd about mine, or do all MK-I's have 3" between the fan and the radiator?

Dan

 

[jlaird]

Oh yea, that is the spare fan belt you carry under the drivers seat. Did I ever tell you about needing a new fan belt on sunday morning when I was out with wife and kids long ago. Spare under the seat.

 

[DanLewis]

Well, now I know why the mechanical fan on a Bugeye sits 3" away from the radiator core! If it is any closer, the top edge of the fan hits the upper radiator tank, which extends far beyond the rear edge of the core! I'm still working on fabricating some sheet metal to better direct the airflow near the bottom of the radiator. I'll update this post with my results when it's done.

Dan

 

[DanLewis]

Well, now I know why the mechanical fan on a Bugeye sits 3" away from the radiator core! If it is any closer, the top edge of the fan hits the upper radiator tank, which extends far beyond the rear edge of the core! I'm still working on fabricating some sheet metal to better direct the airflow near the bottom of the radiator. I'll update this post with my results when it's done.

OK, I have some results to share: It's been 90 degrees here for the last two days, and both days I drove my Bugeye to work and back - about 12 miles one way, all at 65 mph on the freeway. FYI: I have a 160 degree thermostat with a blanking sleeve, and the temperature sending unit is installed in the head, not in the radiator. Both days, the engine temp never got above 185 degrees on the freeway, and was usually sitting at 180. Only when I exited from the freeway and came to a stop did the temperature climb, and then only up to 190.

Here's what I did: As mentioned in the quote above, I was unable to move the fan any closer to the radiator core. The only thing I did was to fabricate a piece of sheet metal that I attached to the top of the front cross member just in front of the steering rack. The metal extends forward, coming within about 1/8" of the radiator core, thus closing the largest open area that is not enclosed at the bottom of the shroud. There are still some smaller open areas on the sides at the bottom of the shroud.

I'll let you draw your own conclusions, but I think it cools a bit better. Jack Laird had mentioned that "Seems that I remember a heavy card board stuff below the fan making up that part of a shroud." Maybe what I fashioned is like that.

Dan

 

[mikephillips]

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.

 

[jlaird]

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.