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MG MGB Technical - uprated radiator?

When I rebuilt my car 5 years ago, I fairly comprehensively hotrodded the engine, at least for a street car. At the time, I had the rad out and had a local shop clean it out.

I've never been really comfortable that I had an overage of cooling capacity. On a hot day, running down the road at 70mph, the temp needle will slowly creep past the N. Idling for any extended period in traffic will cause the needle to go full hot.

I have a new oil cooler, good thermostat and an electric fan in front of the radiator. I'm running fresh 50% anti-freeze.

Amateur engineering analysis: an engine is a heat pump. I'm putting much more heat through the engine than design. It can't be removed with the stock radiator.

Is there a thicker or larger radiator available that is more or less a bolt-in installation that will provide additional cooling?
Art Dodge

Art,

When I put the blower on my TD, I took the radiator to a local shop and had him put in a heavy duty three row core. Based on the more modern core design and fin spacing he said I had more than doubled the cooling efficency of the radiator. I'd even bet that if you took it to a long-established shop he'd be able to tell on sight that it is an MG radiator.
Craig Cody

Craig is right, a good shop can tell that it is a MG radiator, but can get a OEM 4 row L type core from Modine that works very well or can even get one of the more exotic cores from Modine that will give you an excess of cooling capacity. Good luck - Dave
David DuBois

Back before My V8 days I uprated my radiator core with a modine unit that kept my car cool even on the most grueling days. I think I still have that radiator sitting around here somewhere too!

Upgrade the core and you'll be very happy with the improvement in cooling.
Justin

Im using an aluminum rad. (E-Bay) that is supposed to fit a 1965 mustang with manual trans.
but i have to modify the mounts and oulets.
now the temp. needle never gets to the middle of the gauge.
luis rodriguez

Art
Check your temparature with a thermometer. The engine is probably running at 180 f or less. If you search the archives you'll find a lot of stuff on temp, thermostats, etc.

I run a 195 thermostat year around with 1/3 antifreeze, and some watter wetter with my '67 gt.
A thermostat only keeps the engine from running too cool. An engine with a low temp thermostat will run just as hot on a hot day up a hill as one with a low temp thermostat.

Your engine will keep the oil cleaner and get better fuel mileage with a hi temp thermostat. Under hi rpm hi load conditions with a cast iron head, the head will get hot enough to cause detonation under continous hi loads. But a low temp thermostat will only help avoid detonation until the engine gets up to the hi load hi rpm temperatures.

With an overflow tank on my 67 MGB I virtually never add coolant winter or summer.

I am running the small early crank pulley with the late large diameter water pump pulley and the little 7 blade plastic fan with a stock '67 radiator which slows the water pump and fan down. I am using a 5 port alloy head.

The radiator on the 1975 and post smog control MGB is about 25% larger than the earlier radiator.

To verify the guage, I picked up an oven thermometer with a remote read out. It turned out the 38 year old mechanical guage was pretty close in it's temp readings.

Barry
Barry Parkinson

Something i picked up from Peter Burgess when i took my supercharged B to him for a tune up...

The original B rads had three cores arranged in a stagger, such that if you looked through the fins from the front of the rad towards the engine you should see all three rows.

The modern repros have those three rows but arranged in a one behind the other set up, such that the rear rows are directly behind the front ones. That is why the new rads are often noted as having a poorer capacity than the originals as the rear two rows are doing sweet FA for cooling....

FWIW I would think a supercharged engine should be worse at keeping its temp down than any state of normally inducted engine and in comparison you can boost my car into triple figures (VERY quickly! :-> ) and the needle won't shift. I have done nothing but flush out thoroughly the cooling system long before i ever fitted a supercharger unit.

So first off, just check the core arrangement on the rad. Next you might like to try running only 20% antifreeze. I can't remembr the better explanation i have seen on these pages before, but you can get slightly better thermal efficiency by running less than 50% antifreeze/coolant mix (i am assuming by antifreeze you mean /coolant too? If not then in the summer months you ought to run specifically a coolant instead of an antifreeze as they aren't the same)

After this you could consider water wetter - popular with v8 conversionists!

~PHIL
Phil

The issue on trade off of antifreeze vs water is an interesting one. A fluid ounce of Antifreeze will carry fewer btu's to the radiator than the same amount of water. On the other hand water will convert to steam (which has very low density, and will result in hot spots in critical spots - typically in the head) at a lower temperature than antifreeze.

The higher the coolant temperature, the greater the difference between it and the air temperature and the more effective the raditor becomes.

Modern cars get buy with relatively small radiators, even with an air condition condensor adding heat to the system, because they keep the engine heat hi, increasing the temperature differential between the ambient air temperature and the coolant temperature.

It's the difference in temperature that does the cooling.

With a higher temperature thermostat you reduce the likelihood of condensation in the crankcase and get less contaminants in the oil. The car will get better fuel mileage as there is less heat loss to the coolant.

Someone, no doubt has developed an algorithm to compute the trade off in heat transfer for various ratios of antifreeze to water.

Practically, if you have trouble with loosing coolant (i.e. it is boiling off)then increase the ratio of antifreeze to raise the boiling point. Raising the pressure of the cap will also incrase the boiling point. You should use the highest pressure cap your radiator will reliably tolerate. 1 lbs pressure increases the boiling point about 3 degrees f. A 15# cap increases the boiling point from 212 to 257 degrees f.

Typically the problem is not boiling at the radiator, but steam bubbles at hot spots in the head under hi loads. The higher you can increase the coolant pressure the less likely you will get a steam hotspot that can cause detonation and power loss.

Barry
Barry Parkinson

We went back and forth on the most efficient coolant question a year or two ago. Straight water will carry more heat than any antifreeze mix, but does boil earlier and doesn't have the anti-corrosive and water pump lubricating additives. My solution for several years has been to use distilled water and Water Wetter during the summer and change out to the recommended 50/50 antifreeze mix for the winter. I'm sure that the archives will show several different times this has come up.

Paul
Paul Briggs

Have any of you tried Evans npg waterless coolant? It has excellent heat transfer properties, will not cavitate and is waterless therefore no corrision. I know their tech guy runs it in his MGB. Probaly no great advantage for a well maintained stock engine cooling system but I plan to use it when I build up my B engine. http://www.evanscooling.com/catalog/C_npg1.htm
Charles O'Brien

The npg web site is very interesting. The boiling point is 369 degrees f vs 212 f. They do not tell you outright, but it is very obvious that while the fluid is not prone to boil, it also doesn't carry as much heat as water. You must increase the flow rate of the fluid through the engine by, among other things, removing the thermostat. A larger hi flow radiator is also recommended. For Nascar, where fuel economy and power win races, running your engine at 300 degrees f will save fuel while permitting hi horsepower.

I could get by with a very small radiator if I were running my engine at 300 f. However, it appears that the fluid carries 71% as much heat per oz. as water. I think you would find your engine "overheating" by usual standards if you changed your coolant to npg. On the other hand you wouldn't be "boiling" and producing steam, and provided you tuned for the hi temp, your engine would be running more efficiently.

Barry
Barry Parkinson

An issue that I have never seen addressed in all of the discussions regarding heat transfer characteristics of plain water vs water/anti freeze mix is, what is the heat transfer characteristics of a water/water wetter/water pump lube/anticorrosion package? Water wetter doesn't increase the heat carrying characteristics of water, it just reduces the surface tension so that the water makes a more complete contact with the walls of the water passages, which results in a more complete transfer of heat, but the ability of the mixture is never addressed in anything that I have seen. I would suspect that anything added to pure water is going to decrease it heat carrying capacity to some extent.

I still feel that the absolute best way to avoid overheating problems is to insure that the radiator is the correct type and is clean, along with all the water passages in the block, filled with a 25% anti freeze/water mixture. Then a correct thermostat (either 180°F or 190°F), well sealing radiator cap of the proper pressure and insuring that there is no dragging brakes or such. In the 25 years we have owned a MGB, I have religiously followed the above and have never had any overheating problems regardless of where we have driven or the temperature we have driven in. The worst that has befallen any of our cars is a leaking radiator, which didn't cause any overheating problems, just a puddle on the garage floor. Cheers - Dave
David DuBois

Barry take a look at NPG+. There are no changes nessasary in the cooling system that were needed for NPG coolant to work at its best. That is what I'll be using.
Charles O'Brien

Actually, David, I am in agreement with your prescription for cool operation, although running a 25% antifreeze solution would still make me change the concentration in the winter months to get more frezze protection. My prescription was for that car that just won't handle the 100+ F temps that we have around here. I have owned a 70 B that was cool when everyone else was raising the bonnet for cooling at every stop, and that was with a 50/50 mix, and a 71 BGT that couldn't handle 95 F even with water and Water Wetter.

Paul
Paul Briggs

Thanks for all the thoughts and suggestions, this is all interesting.

A little more detail; when I put the car together, in a boffin-like search for the last iota of horsepower, I deleted the belt-drive fan and installed an electric in front of the radiator. I wonder now if the spinning disc and the attendant safety cage presents an impediment to airflow through the rad. Certainly, but to what degree.

Also, what benefit would shrouding either in front, behind or under the radiator do to assist airflow moving through it?

This car has the oil cooler mounted straight in front of the radiator on the shelf, I think I recall the later cars had it mounted underneath. It makes sense that hot exit air from the o.c. shouldn't then go into the water rad, or is that negligible? On that subject, does anyone run an oil line thermostat so oil is shorted back to the engine until it warms up?

Thanks for reading. AD
Art Dodge

This thread was discussed between 10/06/2005 and 16/06/2005

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