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MG MGB GT V8 Factory Originals Technical - Radiators and cooling

Well, my trial with a stock MGB radiator proved for naught. After 3 sessions to run in cam it is obvious that it is not up to the task, though barely so. Sitting in garage running 2000RPM to run in cam, she overheats after a max of 10min. She never boiled over, but the aftermarket temp guage was hitting 240 so I shut down. MAYBE it would work if I was always running at freeway speed, but I am not that unrealistic.. SO I am looking for options.

Falcon radiator: $174+tax locally. Will require $25-40 alteration to get bottom outlet moved to left side of rad to meet Ford water pump.

Recore MGB: $200-400 Also increase overall hieght by a few inches, maintian already modified top and bottom tanks and stock MGB look.

Alum Rad: mortgage on house, kiscked out by wife. most likely require mods to bottom outlet.

Let me know all your various opinions, what you used, what was required to fit the unit etc.. I am thinking that recoring my rad with a good 3row would be best solution, but would like your input.
Larry Embrey

Hey Larry,
Mortgage the house, kick the wife out and go for the aluminium radiator!! It may be a bit expensive initially but I think and by reading a lot of material on this site and other sources, it seems the most efficient system.............And the "Wife/Boss" will get over it eventually!!

Kim Porter

2000 rpm stationary in a garage is pretty demanding, you know. You might think the engine is doing nothing when it is not pushing the car but in fact it is running a massive vacuum pump. You can see the effect of this by introducing an inlet manifold vacuum leak, the revs for a given throttle opening will increase significantly. Not because combustion is any more efficient but by destroying the vacuum the engine is having to do less work. The factory had problems with the midget 1500, I think it was, overheating at idle until they reduced the recommended idle speed by 100 rpm or so.
Paul Hunt

On Saturday I was talking to Dave at the Rover center about just this subject and he seemed to think that a Deisel Discovery radiator might fit, I haven't followed up on it yet. If this turns out to be a dud I was going to recore the MG radiator, however the Falcone Idea seems worth a look. The first I've heard of it. Which model/year?, 6 or 8 cylinder?, what are the dimentions?, capacity?, 3 core 4 core?, anything you can tell me would be good. I'm ashamed to say I know nothing of Fords at all.
Kim is quite right about the Aluminum radiator being the very best, I was looking at one in action on Saturday and as well as being beautiful to behold it performed faultlessly but.. THE COST OF IT!!.
Actualy anything anyone can tell me about anything to do with local (Australia) knowledge about V8 conversions would be wonderful, I'm just about to start. The extent of my progress currently consists of a 1975 MGB parked next to a '86 Rover motor and a Subra box in a Garage 40 miles away.

There are a number of Australian V8 converters (convertors?) posting regularly on this board so you are most definitely not alone.
Hang in there, it will happen.
Cheers, Pete, Queensland.
Peter Thomas


On the basis that my recored V8 Rad only just copes with UK Hot weather and traffic jams, I would go Ali route and save some weight.


Larry, Larry, Larry,

Have you forgotten the lessons of Dale Spooner so soon? :)

Your 302 will need more radiator than my little 215. Bite the bullet. Dale uses a Griffin.

The falcon rad is for a 1963 Ford Falcon. Modine part number 2301. There are a couple versions, one with oil cooler, one with a high perfoemance 3 core and no oil cooler. In US Napa and Schucks are close pricing $169 & 173 respectively.

CARL - No in fact I emailed Dan yesterday and he told me to get griffin, just the $$ is a bit steep for me so I wanted to hear some other peoples experience.

My radiator is CLOSE to handling it, I mean she can run 6-8 min with just MGB stock fans and radiator @ 2000RPM. Like mentioned above that has the engine working hard. I am also wondering if my high flo water pump is pumping to fast for the rad to effectively cool it down?

Now I need to fix my idle problems as she does not want to run below 1500.
Larry Embrey

There is a four row core that is the same size of the mgb core that fits in with minimal fuss. I think I paid $180.00 to have mine recored with that core and DOUBLED the cooling capacity of my system. Can't knock that....



Justin, you have any more info on that core?? $180 is a great price for recoring, what company did the work? Have you run the car and did it help allot?? Capacity double is nice, but did it really help the cooling on actuall running?
Larry Embrey

Right now I still have the 4 cylinder motor in there albeit a built up 4 cylinder -- overbored, better cam, webber downdraft, better distributor, pertronix ignition, and I regularly run it on the highway w/o any cooling problems. Rare is the day that the needle goes more then one needle width above the C and when it does (sitting in traffic for 30 mins or so) it has never gotten above half way. Once I get it driving again for about 10 minutes it drops right back down into the C. Maybe it's kind of freakish how cool the car runs but it's nice to have one less thing to worry about. Here's the shop that recored it for me:

Radiator Hospital
22455 Farmington Road.
Farmington, MI 48336
(248) 478-7900

I told them "I have a 1977 mgb radiator and I want it recored to the heavy duty 4 row model core with the more dense fins" and they said "ok" and off they went. No probs at all. They even reversed my two outlets for the V8 while they were at it! One thing to keep in mind, doubling the capacity of the radiator does make it 1/2" more thick then stock. So if you don't have 1/2" to spare, I wouldn't consider this.

Let me know if you have any questions, maybe I can even help mediate for anyone looking to get their radiator recored.


Bit of an off the wall idea, but for those desperate to get rid of heat, could try placing a modern type heater matrix in each of the front inner wing cavities behind the splashguard. These can be routed into the heater set-up through one-inch grommeted holes in the inner wings.

The cavity has a high leak rate around the door pillar and slash panel so should naturally disperse heat and dry out the wing cavity in the process, which is a water trap and prone to rusting.

I found my last conversion did not overheat if I ran the heater, which is obviously not practical in the summer. The extra matrixes could be plumed in series and have there own cable operated off/on valve.

I may try this option myself, but first I want to see if an uprated standard B radiator can cope.


Nick Smallwood

Justin, so your new core is flush wiht the front and back of the MG top and bottom tanks? I think I can swing that. I got about 1/2" between my water pump bolts and the rad core, so if that extra 1/2" is equal front/rear I will be ok... and can always tilt rad a touch..

Thanks for the info. It is a bit far for me to have them do the work, but I can call them and see what I can find in terms of part number etc.. then see what locals want to charge.. Did you say you had it made taller too?? I will probably do that, 2" or more if possible..

Larry Embrey

I hate to say it, but its time to buck up for an aluminum radiator. The last thing you want to worry about, when your stuck in that "wonderful Seattle traffic" is over heating sitting on the ship canal bridge with no place to pull over. Been there, done that, now that I have the alloy radiator, I don't worry about overheating at all. Its nice to be able to enjoy the drive without having one eye on the temp gauge and the other on the road!
I got a flier from Dan at D+D, he is selling alloy radiators that should bolt right in. They are $400 I believe. Another plus with alloy's, they are lighter, any time you can reduce the weight ahead of the front wheels, improved handling is the result. Best $400 you can spend on your conversion. OK I'll get off the soap box now!!!

bill jacobson

Larry, get your radiator rebuilder to show you his catalogs and to explain the different core types to you. It makes a big difference. Just getting a four row core doesn't guarantee the radiator will cool any better than the stock one. Spacing between tubes, tube size, tube wall thickness, fin count, and fin type and construction all make a big difference. Louvered fins, fin to tube attachment method, folded or flat fins, etc. If you want a seriously efficient radiator you should make a study of these factors and design the core yourself using the options available in the catalogs. You will have to pay a little more than for a "standard" core and will have to wait for it to be made for you, but it will be worth it. For instance, I had the radiator on my truck recored with a standard core and the results were marginal. As (bad) luck would have it subsequently the fan took out the new core and I went back and did as I now suggest you do. The new core had the same number of rows, but I selected elements to maximize it's cooling capacity. The result is like night and day. Since then the truck always runs cool no matter what. The special core cost me an extra hundred dollars and a week's wait, and I'd do it over without even a thought.

The radiator I have in the MG is a 5 row using very small tubes, which was suggested to me by a radiator shop several years ago. The top and bottom tanks are custom made from sheet brass, and it is a bit thicker than a stock tank as well as longer. It was very expensive but it seems to do OK. If I was doing it over though I would select a somewhat different core I believe, due to some of the limitations of the small tube and because I think I could actually get more cooling density using somewhat larger tubes. One thing to look at there is tube offset. It is not necessary for all of the tubes to line up in each row. That is to say the rows can be staggered. This area is a science in and of itself and if you want good results you really have to look at the core manufacturer's recommendations. Most of them make all or most of the more common configurations and can easily provide specials on request.

Jim Blackwood

I have been dealing with cooling a V8 MGB for about 15 years, driving the beltway & D.C. traffic, using the car(s) as daily drivers, & for the last 5 or 6 years, have compounded the problem by adding A/C.

I will share a little of what I have learned. The stock 1977-80 MGB radiator with modified tanks, 4 row high efficiency core 2" longer than stock, louvered fins, will cool most V8's without A/C, & mild engines with, IF,IF you add a 16" puller electric fan with a capacity between 2700-3000 cfm & you do what you can to enclose, or duct the radiator so all the air passes throught it, rather than go around it. Ideal cooling mixture is 25% antifreeze, or straight water without A/C, & the proper additives for anti corosion. Run a 15 lb cap, 180' thermostat.

The Falcon or Mustang radiators are an acceptable substitute for the modified MGB unit, but are over 2" longer than stock, & may cause ground (debris) clearance problems. I mounted mine at an angle. You need to move one hose connection, as they are both on the same side & may (will) short cycle the coolant.

More than 4 rows in a copper/brass radiator is diminished returns. The wonderful 6 row radiators have the tubes more widely spaced than the 4 row units, & nothing is really gained except you can say you have 6 rows.

The biggest cooling problem is getting hot air out, not cool air in. The MGB engine bay is a high pressure area, & you have to fight to get air to pass through the radiator. No radiator is efficient unless air moves through it. Use RV8 style headers & lager than necessary holes in the fender, add louvers in the inner fenders, or the hood. Anything to improve airflow. Timing & air/fuel mixture affect engine temps.

Aluminum radiators are not all equal. Require a minimum of 1" tube size, 1 1/4" is much better. A OEM aluminum replacement radiator is little better than copper/brass, a performance model can be a big improvement.

Add an oil temp gauge to your dash & watch the thing. If you see oil temps 30' higher than water temps, you need an oil cooler. Add a thermostat to shut off oil flow untill warm up & in cold weather.

I run the hell out of a warmed up 4.2 with A/C, using a Be Cool 1965 Mustang Aluminum radiator with 1 1/4" tubes, 16" 3000 cfm fan, & it keeps me out of the red. I did have to add an oil cooler, but I live with 95' temps, 80-95% humidity, & 4.2's are known to run hot.

Each engine has an ideal idle speed that moves the water fast enough without generating undue engine heat. Start with 850 RPM's & find you ideal speed, it will help a lot. Too low, you build up heat by not passing enough water through the cooling air.

Mike Moor cools a 300 Buick with an aluminum rad from Summit, 22" x 19", I believe, but he had to notch the frame rails to get it in. He has also louvered the hood to let the hot air out.

Your experience may vary.

Jim Stuart

If you have a look at the thread - "heating mytery ..." you'll see that others have experienced better cooling with the heater running. However, the improvement seems not be be a function of the extra cooling provided by the heater matrix but rather the result of better circulation of water and dislodging a steam trap.

Hi Marc

That would make sense as the difference between heater off and heater on seemed greater than the effect of such a small radiator.

So maybe a single heater matrix hidden in the wing cavity would work allowing someone to benifit from better flow and bleeding in the summer without cooking themselves in the cockpit.
Nick Smallwood

Nick, It wasn't a question of how much flow, only that some flow will avoid whatever the problem is - probably a steam trap. Having another matrix won't make any difference and it seems that you should be able to introduce flow by using a waterhose to some outlet at the pump somewhere. I haven't sussed it all out as I have just emerged from NHS hospital after an emrgency appendix operation and won't be able to get stuck in again for about 3 weeks.
Ask Paul Hunt, He has the necessary plumbing on his V8 and has no cooling problems, heater on or off.

I would like to know about this steam trap. How about it Paul?
Jim Blackwood

Whoops. I didn't mean to drop Paul in it. His car has this hose but he is almost as mystified as I am - but he'll probably make his own contributon here quite soon.

"... if I ran the heater, which is obviously not practical in the summer..." but sometimes essential...

Jim - the factory V8 has this 'steam pipe' running from a small-bore extra pipe on the thermostat elbow to another one about mid-way along the inlet manifold on the LH side. Some years ago I read about it causing a really wild temp gauge when it gets blocked. Some time after that I started getting said really wild temp gauge - like 60psi on the oil scale of the dual gauge! This was shortly after starting up but it continued to cycle madly from time to time after that. Got home and checked and found the pipe into the manifold blocked. Cleaned both out with a twist-drill and confirmed I could pump clean water out, and replaced the hose, and it was as right as ninepence. Driving Marc's car with the heater off was very similar. I reckon a similar small-bore pipe bypassing the heater core would do much the same job without sapping too much heat when the heater is required.

If your electric fans *don't* cut in when the gauge is reading high, as neither Marc's nor mine did, is a good indicator of this problem and cure, I think. Why they don't is a mystery to me, since the two sensors on a factory V8 are only a couple of inches apart.
Paul Hunt

Interesting. I'd like to get a close look at one of those intakes some day. The US intakes have the two rearmost water ports blocked off by the manifold, and of course there are no water ports in the center of the head, leaving only the front ones to connect to the thermostat housing. Normally a water jacket under the intake runners lead back to a connection for the heater hose at the rear of the intake. One wouldn't think that there would be anything you could do to that water jacket which would affect engine cooling very much. But apparently there is. How curious.
Jim Blackwood

Paul. How about putting pictures of this set up on your website? I'm sure that everyone would appreciate it. I'll check mine when I get home now to see if I've got this pipe.

Ian T.
ian thomson

Picture posted - - it is the pipe in the foreground with the dashed white line.

As far as the rest of the circuit goes, a short hose about 1" dia comes off the back of the water pump and goes into the inlet manifold. On the back of the manifold is the heater tap and inlet to the heater. The return from the heater goes to a metal pipe that runs under the inlet manifold for its full length, with another short hose about 1" dia from that to the top of the water pump.
Paul Hunt

Interesting. Are the rear water passages from the heads blocked off as well? Otherwise it looks very similar to a 215 2 barrel intake, except for the hose of course. The turbo intake had an extra hose barb for cooling the turbo, but it came off the elbow for the heater.

That hose would act as a thermostat bypass, since it crosses the thermostat, and I have heard of instances where thermostats were drilled with a small hole to allow steam to pass through. In fact it used to be pretty common. As I recall (btw, what does IIRC mean?) some thermostats had a sort of ball check of some kind in the plate. Of course with a vertical mount you'd have to be sure to get it to the top.

That may suggest a simple modification which could help with cooling on some of these engines. A 1/16 to 1/8" hole could be drilled in the thermostat plate just inside the sealing edge and positioned to the top. That size hole would not flow much liquid at the pressure drop it would see, but it would vent any steam quite nicely. Hat's off to you fellas for putting us onto something that may prove quite useful.

Jim Blackwood

HEY "Good" news! I had problems with the carb and the car would not run below 1400RPM. after a quick tear down clean and rebuild it ran like a top. I also adjusted timing. I then ran the car at Idle for 20min, nothing but stock MGB rad and stock fans. SHE NEVER WENT OVER 195*!! YAHOO!! Time will still tell, but wanted ot let you guys know, there is a glimmer of hope..
Larry Embrey

Not aware of any ports on the back of the heads. I have seen the thermostats you mention, certainly the ones with the ball valve, possibly the ones with the hole. AFAIK the V8 uses an off-the-shelf thermostat, nothing special, even though it is mounted vertically instead of horizontally like the 4-cyl.
Paul Hunt

Paul, I think Jim's talking about the rear water passages on the heads blocked off by the intake manifold. The passages (in the heads) are necessarily there to allow the head to be used on either side of the engine. Typically, U.S. engines block these off so the coolant flow is water pump-front to rear of block-rear to front of heads-thermostat-radiator...
From pictures I've seen, it appears to me that at least some Rover intakes have a rear crossover in the intake manifold with a heater tap. While this doesn't seem to be the best place for hot coolant (that would be in the front of the engine) you can't argue with success.

Wayne Pearson

Right, I did wonder if there was a passage from the manifold to the heads, otherwise manifold heating would be dependant on the heater control.
Paul Hunt


I just ran the car outside in sun with the hood on and closed, heater flow turned off. She ran 20min and never hit 200*F! YEAH!!

I will let you guys know, carb tune and Ignition timing make a HUGE difference!! I found that my car was lean and that timing was way off. That is all that has changed on the car to have it go from overheating to running like a charm..
Larry Embrey

I've heard varying the timing from stock can affect overheating dramatically, though I don't remeber if the advice was to advance or retard.

Paul, yes I was referring to the coolant ports in the head that connect to the intake manifold as Wayne suggests. I was wondering if the rear openings in the heads are blocked off or connect to the water jacket. in the intake. I do not know how much coolant circulates in the intake water jacket without them, I suppose there may be some eddy currents.

Jim Blackwood

Had the opportunity to look at at factory V8 inlet manifold off-engine this morning. There are ports from the manifold to both heads, but these are right at the front of the engine not the back. The manifold does extend to the back of the head, but the last few inches is solid. However from marks on the manifold it looks as if the solid area could have lined up with ports in the gasket and hence possibly the head, but there would have been no flow, of course.
Paul Hunt

Then that is consistent with the 215. It sounds as if that steam vent may be relevant.

Jim Blackwood

This thread was discussed between 22/04/2002 and 27/04/2002

MG MGB GT V8 Factory Originals Technical index

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