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MG MGB GT V8 Factory Originals Technical - Radiators

Stock MG radiators cool stock MG engines adequately (if the rads are in good shape, which they often are not).

To ask them to also cool a V6 that is almost double the size (or a similar or larger V-8) is asking just a bit too much.

The decision was even easier in the case of my Jamaican conversion as we had removed all of the factory brackets anyway and while I could have simply built a new rad from MG bits (I use a double thickness core with mga top tank and MGB bottom tank on the Twincam race car), I decided to look further afield.

I researched what stock rads were a suitable size with outlets as I wanted them, but worried that most of the ones small enough to fit were meant to cool engines about the same size as the MG was originally. Finally I went to the racing specialty market and ended up with one I thought might be of use to some other MG conversions (if you didn't already find this one yourselves).

It is a 3" thick 21.5" wide 13.25" tall all alloy rad, with welded tanks, not the usual commercial pressed plastic tanks with gaskest that can leak. It has both inlet and outlet on the left where I wanted them and the filler on the right, although you can get other versions. It costs $230 and is available at the usual outlets (I got mine from Summit). It is made by Afco for drag racing and is part number 80105N


Hope that is of possible use to someone.
Bill Spohn

Bill, sounds like it will be great for your car. I have an early B radiator in my 2.8V6 midget and it cools fine for that combination with an electric fan. I can't remember what radiator Bill Guzman recommends for his V6 conversions, perhaps he'll add some information.
Bill Young

I though there was only aboyt 16 - 17 inches between the chassis rails and the one you quote is over 21" wide, does it sit above the rails?
Tony Bates

Tony--not sure about this rad Bill is talking about, but i have used a 1965 Mustang 4 core brass rad for the past few years with my Ford 5.0L V8. I bought an alloy (part # CR5064) same size this fall and will install it in the spring part--it was a deal at 349.00 from Not sure if they are still available at that price.Its a good rad with welded tanks etc and outlets were available at different locations to fit water pump setups for Fords.It fits nicely between the rails and has great capacity to cool the V8.
I never felt the brass rad was adequate while standing still as the heat accumulation under hood was a problem even after I ceramic coated my headers and louvered the hood (bonnet).This really only was a problem in very hot weather though.Hope this can help somebody
Gil Price

Ditto, Tony's statement. the max with between my frame rails were 18". my custom Griffin Rad.was 18'X 18" , side tanks and 2 rows of 1 1/4" tubes. how did or will you mount the 21" wide?. the 18" tall left the bottom even with the lower valence and i used a F/G MGC hood.
good luck
kelly stevenson

In my 67 GT with a 2.8 V6 I use the stock radiator with an electric fan.
The stock radiator water capacity is very close to that of a S-10 or Camaro.
The capacity is important but more important is how well the hot engine bay air is evacuated.

One of the big problems when swaping the engine on a B is the wiring use to power the fan. The wiring will show 12v and less when the engine is running and even less when the headlights are turn on. (some cases)
Always use a power relay to the fan and fuel pump, if possible use new wiring.

In our 74 RD I use a radiator from D&D is larger and is alum. I also I use an alum front closure to prevent hot air recirculating back through the radiator, this is worth about 15 degrees. This car is use to test at the track in temps of 105/115 with track temps of 140/150 it runs 210 and 220 at idle.

The 67 GT with stock radiator on a hot day 90 and mild traffic it runs 200 and at idle 220.

GM V6 normal temps for the engine on 95 temp is:
running 200 to 220 to a max temp of 240 with a 17lb cap
will start to boil at 245 this is a sea level. It should cool as the engine starts to get outside air through the radiator (driving)

If the V6 is going to see hard driving in hot weather then use a Mustang, Comet, Falcon radiator from Napa this fit with minor mods or just buy one from D&D.

If normal driving the stock radiator is good enough, just make sure the hot air is evacuated and the electric fan is getting over 12v with a new relay.
Bill Guzman

Like Gill, I have gone with an early Mustang/Falcon rad and like Kelly, used an MGC hood
Tony Bates

bill s, i ran my b rdstr with a stock 1978 mgb radiator for several years, my engine had several mods and produced quite a bit more hp than a stock 3.4. i ran with the stock fans for 2 years and than replaced them with a single pusher on the front a couple years ago, it came from a honda performance shop. the car never ran too hot or ever overheated, in fact i removed the oil cooler as it ran too cool during the first season. a properly cleaned and conditioned mgb radiator is more than enough for a v6 conversion, this is part of the beauty of this swap. jim
james madson

I agree with Bill that the stock radiator holds plenty of coolant and has a large enough core for most of our cars, if it's in good condition and if you're willing to systematically go through and optimize the rest of the cooling system (such as the fan wiring, etc.)

I've been using a stock MGB radiator core year-round in all driving conditions with my Buick 215 since '92 and it hasn't overheated yet...

Hardly anything else about my cooling system is stock. Here's a list of things I did, in case someone wants ideas. I:

* soldered oversize ports into the MGB rad, and removed the filler neck.
* fitted an overflow bottle (ex VW Jetta) high on the passenger-side firewall so it facilitates easy bleeding of air from the system and also keeps a column of water above the inlet to the water pump (so it won't cavitate.)
* changed the radiator mounting so the whole core is used, and so cool air can't bypass the radiator or recirculate back around the radiator.
* fitted two nine-inch Honda Civic fans (pushing) with close clearance to the radiator fins and with fan-rings. (These were cheap from the junkyard! I didn't fit an engine-driven fan.)
* used 12-gauge wire to assure plenty of current to the Honda fans. IMHO, electric thermostats add too many potential failure modes, so I use a toggle switch to turn on the fans.
* removed and threw away the MG oil cooler, and the car's original grille (in favor of a simple wire-mesh screen) and I further streamlined airflow in front of the radiator with simple sheet-metal ductwork. I also have an air dam fitted below the chrome bumper.
* removed the car's heating system, and I use the fresh-air from the cowl for engine intake (so the engine doesn't breath heated air.)

One thing I didn't do that would've dramatically improved cooling would've been taking the headers through the wings. I didn't find any need to wrap the headers, or buy any other expensive materials.

My MGA has 22" between rails - more than the MGB I guess. Good thing that the stock MGB rad does the trick.

The rad I am using could probably still be used in the MGB as it is fairly shallow - just cant it on an angle so the bottom tank mounts above the obstruction? I'd check it our but I only have the MGC handy and it is fairly full of rad on its own......
Bill Spohn

I am still running a stock radiator. As has been said it is airflow that is more important than capacity in our situations. I know once I am moving my car is actually bouncing off the thermostat just like a normal car, rock steady. when I stop it might creep up a little bit, but with the dual rad mounted 8" fans she stays right around 205 (stock temp is 195)

IT all comes down to airflow.
Larry Embrey

This thread was discussed between 28/12/2005 and 29/12/2005

MG MGB GT V8 Factory Originals Technical index

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