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MG MGB GT V8 Factory Originals Technical - How hot does your V8 run?

I wonder if we could take a simple poll: how hot does your V8 run on a fairly warm day (let's say 80 degrees, sunny, around-town type driving but not parked in a traffic jam)? I think my car is too hot ... water temp is 200-210 degrees F. I mean, it works just fine but I wonder if this is abnormally high. The gauge is always to the right of N, and sometimes fully halfway between N and H. Seems kinda hot.


Mine runs 185-190 degrees F. The fan comes on at about 190F.
bill jacobson


excellent idea.

Two points to clarify
First which engine size also what state of tune
When I was running a 3.5 stage 2,the guage sat on N - This was with new water pump but standard yellow fans and standard V8 Rad.
I'm now running 4.6 stage 2, the guage then started running towards hot. As I use the car everyday for work, over the weekend I had the Rad enlarged. The guage now sits just to right of N sometimes rising slightly but quickly coming back to N. Not perfect but coping with 90 degrees.

What is the optimum operating temp for the range of engines.

My conclusion in the conditions indicated is a 3.5 can use a standard cooling system if in good order especially with a better fan system.

The 4.6 probably needs an aluminium Rad and a better fan system.


Paul, what do you mean you had the rad "enlarged" -- how, specifically? One reason I'm a bit dubious about putting on an alu rad is that I have been told again and again that aluminum rads do not last nearly as long -- they are good for maybe two years or so -- then they encounter cracking problems. Cambridge Motorsports sells an alu MGBV8 rad but good heavens is it ever expensive. If it's short-lived to boot, seems like a lousy deal all around.


I was also informed the Alu rads have a short life.

Enlarging from 3 Core to 4 Core. Reading the Stewart site you may get say a 15% increase in Heat dissipation but because of the lower water velocity this is probably reduced or could make matters worse. All I can say is that it did cure my overheating problems and I have not yet changed from the twin yellow fans. Fitting a more powerful water pump would be the answer to the loss of water velocity.



I should also add I am using short nosed water pump.

I also understand Alu rad gives a 30% increase in cooling.


I was asking a company in Suffolk about ally rads and they reckon that they last longer because they are more flexible. They told me that the welds were ally whereas the welds or joints (whatever) on a coper rad are brittle and more likely to crack. That differs from what you have been told, Paul and so here we are again not knowing what to believe.

I measured my crank and water pulleys. The crank pulley is 6" and the water pump pulley is 7". This would partly explain the excellent performance of my car, I supose, and also help to explain the overheating as my pump is being underdriven by at least 14.3%. I reckon that a ratio of 1:1 would produce a significant improvement in cooling.
Paul what are the respective sizes of your pulley wheels?

I was told that they give you a 15 - 20% improvement!!

Paul there is a question from someone called Sandra up on the Stewarts Bulletin board about the diffrence between ally and copper rads. Should be answered tomorrow I expect.

Paul, by "short nose" do you mean one from a Buick 215? If so, do those have the water inlet angled back a couple of degrees, like the factory MGBGT V8 water pumps, so that the lower hose clears the fan belt?

That's pretty incredible that you've gotten away with using just the yellow fans! I have an engine-driven fan too (if you use a certain type of flex fan, I forget the brand, it fits even with the long-nose water pump even though it seems hard to believe that it will when you look at the motor) and I'm still running pretty hot; without it I think it would be hopeless. Hopefully synthetic motor oil isn't quite as sensitive as regular oil to the higher temps. The car runs absolutely perfectly, just hot! And it's going to be a really, really hot summer here ... fortunately there is not much traffic.


Yes, Buick which is available from Real Steel in UK.
The additional width of Rad may mean a puller cannot fit.


I was quoting from MG Owners Alu Rad - which I believe is a double pass which may give rise to velocity problems again.

I will have to take a look under bonnet to answer other questions.

I am using oil cooler and Valveline 20/50 with no probs on oil temp.

The info on Alu rads I think came from Doug Smith MG Motorsport, so it may make a difference whether you are selling or just advising.


I had my radiator work done by a local guy here. He is one of those old guys (older than dirt) that has been doing radiators since he was in high school (before I was born, and I am not a spring chicken) He took one lok at my stock MG radiator and said it could handle cooling my 302 without problem, just keep air moving acrost it and you will be fine. He backed this up by pulling out some stock stang radiators and showing me the difference and how they affect cooling. MG radiators are heavey 3 row units, and if they are in good repair they should be fine. Time will tell when I get it running and test it.....
Larry Embrey

Only Bill Jacobson has answered the original post. "how hot your v8 runs", the rest are going into radiators and water pumps which is fine, but, lets keep this subject to numbers 180 deg. F to 200. will be fine

Fair enough, Romney but Paul is quite right. If people are going to make any sense of it then we need to know a bit about the system which is producing that level of heat - after all, even Harry in the original posting introduced variables concerning the weather and the kind of driving and his criteria are much less specific than size of engine etc listed by Paul.

"Works", GT V8 3,900 cc John Eales Blueprinted engine on SUs giving over 216 bhp. Standard radiator, single Kenlowe pusher fan, normally 180 to 190 F.

Can exceed 210 F if standing still for a long time in high ambient conditions, IF not precluded by manually switching fan on in anticipation - fan switches in normally at about 185 F.

In practice cooling is not a problem.

Safety Fast

Nigel Steward

I fitted an uprated rad (same basic physical appearance but some 25% more tubes) to my factory V8 as I found that when stuck in traffic on a very hot day (90F +, it does happen in the UK sometimes) the needle got up into the red even with the fans running full time. The new rad helped, both in keeping temps down in traffic and how fast it got back to normal when underway again. I also fitted an SU fan switch in place of the Otter as the latter seemed to be drifting up before it would switch on, now the fans come on much sooner which also keeps the hot idle oil pressure higher. On a trip to Le Mans I and another V8 got stuck in traffic on a warm day and the fans were not able to reduce the temp, barely maintain it, so I turned on the heater fan too, but even with both on the needle still didn't drop below 1/3rd the way between N and the red. I was a bit concerned, but afterwards discovered that the other chap had to do the same thing too. However my system does seem to get hotter than his and run at a higher pressure, I have to change the rad cap every year as it tends to chuck some water out of the overflow after switch-off when the cap gets a bit tired.

Paul Hunt

Exellent, yes variables that affect temperature make alot of sence. can i sugest the following:
lets post temperature the car is running, ambient temperature, type of radiator, conditions when driving (slow,stuck in traffic, etc) and stage of tune of motor.


I'm trying to be as helpful as possible, but I only have a standard V8 guage. Anyone give a guide to temp around guage ie at 6,5,4 o,clock.

Also how about a few details of your own car.

I was running a 3.5 with approx 210bhp and did not have any cooling problems. I'm now running a blueprinted 4.6 with say 265bhp with symptoms described above by Paul H. The larger rad did cure the problem but I'm still waiting for traffic jam with 90+ temp to be totally convinced. I still consider it is running slightly hotter than optimum.


What size Kenlowe pusher are you using?


Five o'clock on the stock guage when held up in traffic at 82F ambient with both stock fans running.

(165BHP at the wheels - lucas fuel injected RV8 engine - five year old stock rad - 30% antifreeze/no water wetter - lagged block huggers and no extra holes pro tem ).

One could say that the car operates normally in any reasonable ambient temperature provided both fans are working - (this includes towing) however the temperature under the bonnet is high enough to make plastic deteriorate and the plug leads and coil need regular replacement. The looms will not be long life either) For me airflow is the single critical factor.

Roger Walker

my car is off the road for now, because of a full resto from top to bottom and from front to back, hopefully it will be on the road in the next 2 to 3 weeks this time with a 1980 Rover 3.5 litter fully blueprinted and balanced around 220 H.P.
The prior engine was a 3.8 litter buick stock tune with block hugger heathers, no louvers on hood, but had a ford falcon radiator, core size 17.5 x 16.5 i ran it in 102 deg up the mountais of Idaho temperature gauge showed half way between N and H but never boiled over nor i ever lost coolant.

I'm glad I started this thread. Coincidentally, I was disconsolate today to see for the first time ever, my temp gauge needle hit H. Super hot ambient air; bright sunshine; stuck in traffic near Washington. Didn't boil over (and no, I'm not goofing around with that 32# cap any more, back to a 15#-er) and it didn't run any differently than normal, but it seems pretty clear: there's no future in it. Gotta re-think the whole system. And here I thought I had been particularly manly for shoehorning a crank-driven fan in there, in addition to those silly yellow things. Other than that fan, my setup has all the things fly in the face of reasonable cooling: block hugger headers; 3.9 with heavily massaged heads; no hood vents; no fender well vents (NB for religious reasons I am opposed to them); no oil cooler; regular factory V8 rad. I s'pose my running lots of vac advance -- though it seems to save a little gas on the hwy -- doesn't help either.

It's time to turn over a new leaf.

I have a 1977 V8 conversion (rover 3,5L) with the V8 radiator from the V8 conversion compagny. After installing the V8 i converted the car from rubber to chrome bumper and this reduced the temperature a lot. Now it is at the 12 o'clock positon and in very hot wetter sometimes in the 1 o'clock position. I have the 2 standard fans but installed a kenlowe kit to get the fans on earlier.
With rubber bumper fitted, it used to be often in the 2 O'clock position.
peter van de velde

I have a 79 rubber bumper with a Buick 215, block hugger headers,new V-8 rad with stock pushers that run all the time.I also cut holes in the lower inner fenders.On an 80 degree day it runs about 200-210 degrees.I too think that is a little too hot for my liking.I would like to be around 180-190 degrees.Any suggestions on how to drop 20 degrees without spending a lot of money?
Ken Blough

Thanks Romney- Won't be long before you can test your cooling system.

Harry - pump is not angled back
Marc - Crank 6in Pump 7in

Ken- You could experiment with Water Wetter and let us know whether it does reduce temp.

I use Water Wetter but no idea whether it works.

I also use later front valence which has two inlet holes.

In addition because I use a steady bar, I've moved expansion tank to rear of engine bay and rad cap now sits above Rad.

Ken - With my limited understanding of cooling systems, I thought fans added nothing above 30mph and in fact it's better to lock the fans in place.


Paul, Stewart's site says that water wetter doesn't work and they explain why. They reckon that the best thing to use is pure water - distilled if you live in a high mineral area and to use as little anti-freeze as you can get away with. If there is no danger from freezing then they say use a corrosion inhibitor only.

Another site :-
says that you must choose your inhibitor to match your engine material - ferrous or aluminium. They also reckon that the inhibitors which protect aluminium breakdown quite quickly and that if you are using antifreeze which contains sillicates - which protect aluminium, then it needs to be changed fairly regularly.
Are most people relying on electrical temperature gauges which only give C N H readings? Even if the gauges are properly graduated, if cooling is really a serious issue then we should be upgrading to a proper mechanical capillary gauge which I understand is very much more accurate. These can come with adapters which fit into the sensor hole normally occupied by the electrical sensor.


Stock 3.5L Rover, federal injection, four row radiator extended down about 4" past stock, 1300 cfm pusher fan, no apron around radiator, no holes in fender wells, chrome bumpers, 60% antifreeze.....

Runs 185-190 on the thermostat for about the first 10-15 minutes of a trip, but will run up to 210 if allowed to idle in hot ambient. Getting moving doesn't seem to reduce it much once if comes off of the thermostat. (Suspect air just goes around the radiator instead of though it) The ambients around here will swamp the cooling capacity of my current system causing it to rise above the thermostat, but it has never boiled over.

I've got a capillary temp gauge installed that I calibrated with a pot of boiling water on the kitchen stove. While it is still hot here, I'm going to run some OFAT experiments and see what seems to work. I have a metal section in the suction line of my radiator return hose, and I think I'll weld a bung in it and put in another capillary gauge so I can measure the delta temperature across the radiator. Any suggestions on what factors to test?

Surely one of the things that contributes to overheating is all that heat radiating from the headers inside the engine compartment. I had mine jet-hot coated and that's made a significant difference, especially when I start working the engine hard. Coolant temperatures are lower now and lifting the hood on a hot day is no longer like opening the door to a furnace. With a V8 and block hugger headers you might want to consider it. Click on this:
Steve S.

Steve, I did have this done; no question, it helps a good deal. Still -- sigh -- she's running hot. It would just be antithetical to me to install hood vents, but I think I'm going to get a second hood and try just that. Reason being, when the hood's up it can idle for an hour in 100-degree noonday sun, and it won't go past N nor will the electric fans kick in -- and if you tried that with the hood closed the car would almost definitely overheat. So my primitive reasoning is (as many of you concluded long ago -- I'm a might slow) the limiting factor is getting that hot air flushed out. If I can figure out a way to build in drains under the hood vents, so rain doesn't just slosh all over the motor (the car lives outside), I think I can swallow hard and get vents.

I have an 80 LE with a 3.5L Rover, a new factory radiator & stock cooling fans.
I use the car for my daily commute from Bowie to Dallas & back (a round trip of about 170 miles).
In the morning the temp stays a needles width
below normal & comes up to normal during the city part of the drive with an outside temp of 80*F.
In the afternoon the temp hovers a needles width above normal during slow highway traffic then back to normal as speeds increase with an outside temp of 90*F.
My car doesn't seem to mind ticking over in traffic, but gets a bit warm during stop & go traffic with the temp indicating 3/4ths of the scale up to just shy of the red.
Today during stop & go traffic the needle got into the red, when I stopped & popped the hood (bonnet)to splash
water on the radiator,I saw one of the cooling fans wasn't running "duh!!!" After I fixed that & poured a half gallon of water on the radiator the temp was back to normal & off I went.
I don't think these cars running warmer than we would like is abnormal or cause for major concern "It's just the nature of the beast".
I can't wait until it's a 110*F outside I'll probably be eating those words.


Dwight McClain

I see that you cut holes into your wheel arches. I was considering the same move - maybe 3 1.5" holes on each side with shields to prevent entry of water and muck into the engine bay. I was thinking of putting the holes where I might want to run RV8 exhausts if I decide to go that way some day.
Did the holes you put make any difference? How big, how many? Any one else tried the same thing?

Hood vents: I'd like to try these- what fits easily from other cars?
I thought about the vents from a Datsun 280Z, they look OK on a Datsun but will they work a 'B hood- anyone tried them yet or have any better suggestions?
anthony morgan

Anthony, Check the archive for previous threads on bonnet ventilation - lots of material there. Frankly I'm trying to keep the outside of the car looking pretty original.
I've now cut two 2" holes adjacent to the manifolds inside each wheelarch. I have to say that there is no discernible difference on the temperature gauge or to the level of heat inside the car but you can feel a flow of hot air coming out into the wheel arches now so there must be some difference. I intend to cover shield the holes with aluminium louvres to prevent road muck gettingto the bay


I change water on a regular basis. I'm still waiting for a heatwave to test cooling system with Water Wetter and then flush and try without.

I checked think automotive web site - they have electric pump with a motor life of 2000hours-seams a bit of a short life.

I've never been happy with these holes in the shell and would probably need reinforcing. If going that route can a small fan be fitted to extract air.

The RV8 is reputed to have a much better airflow through the rad, are there some adaptions that can be made to B front end?


Sounds familiar - must be the stock fans we are using.


It occurs to me that the Rubber Bumper models have a slotted front apron in common with the original V8 models. I seem to recall that yours is a 1974 model. Some of the late production 1974 models had this slotted apron. Does yours? The slot was to increase airflow for cooling. Without it, the V8 radiator has a hard time doing its job. Then again, we may be looking for something complex when it's actually something quite simple. Are you using the strip of foam rubber to close the gap between the radiator and the body? I found that this is essential for allowing air no other passage but through the radiator, even on the four cylinder model. Without it the pressure of the air on the face of the radiator is decreased as it bleeds off through the open areas, thus decreasing cooling flow through the fins.
Steve S.

Marc, thanks for the reply to "hood vents".
So I went to the wrecking yard and bought a couple of bashed up Datsun 280-Z black, moulded plastic hood vents- I reckon if I enlongate the slots with a router and fix the vents to the hood just behind the lateral hood brace and then fabricate a drain tray under them, the underhood temperature will be reduced quite significantly. I like the look of these things too- used hoods are fairly cheap in my region so if it ends up not working too well, I'll get rid of the thing and try my next whacko idea which is a cam-operated device to raise the hinges at rear of the hood from a simple lever inside the cockpit. I stole the twin cabled hood release lever and mechanism from my Dad's old XJ6 for this caper, his car doesn't run so he won't be needing it for a while yet :-)
Anthony Morgan

Steve, I have the valance with the holes but I didn't know there was a foam rubber piece that you can use to seal the top of the rad against the hood. Seems like it would be a great idea. Do you know anywhere they sell such an item? ... is this a standard part from a RB 4-cyl car?

I have also heard, I think, that some people use a scoop or whatever you call it to get air up to the bottom of the rad(?) ... do you that would help and is that a standard part as well?

On removal of air: Realistically, the only place there is for the hot air to go is down, if a stock appearance is retained, and this is contrary to nature. At a slow speed or stopped this is a problem, especially if sealing around the radiator isn't up to snuff, as the same hot air will recirculate through the radiator even with a proper fan shroud. So sealing off the front is a big concern. See if you feel hot air on your feet standing beside the car with it running. To get the air out while moving, use of a decent front spoiler (or air dam) will help lower the air pressure under the car, and of course will be more effective the closer to the ground it rides. For surreptitious venting I have another suggestion which I haven't seen mentioned here. The body has stiffening members running from the firewall at the windshield corners to the inner fenders, and the inner fenders have fairly large openings into this area alongside the master cylinders and fuse block. Openings can be made in these reinforcing members without weakening them substantially, which would allow a considerable amount of hot air to flow into the wheelwells from high in the engine compartment. These openings would only be seen if one was looking for them. On my car I've gone a step further and mounted a 4-1/2" fan on each side further back, and these will blow air out through the rear of the fender and rocker, but there's no reason a "sleeper" couldn't use the idea.

On radiators: Copper/brass is somewhat more efficient than aluminum. It will resist the elements a bit better as well and is easier to repair. Also heavier. However, the single biggest factor affecting the life of any radiator is usually the quality of the water run in it. Pure distilled water is a non-conductor and will not support galvanic degradation of the system components. Almost any impurities will contain salt and will immediately reverse this. Rust inhibitors, water pump lubricant and anti-freeze are essentially the necessary evils. Incidentally, The radiators from most american cars have a less restricted airspace and airflow and this should also be taken into account.

Timing has been said to be one thing we can do with these engines to help regulate the heat. I believe there is relevant information in one of the earlier MG-V8 Newsletters but do not recall the specifics. Eventually I will look for it but maybe someone else remembers. However, beware retarding the timing too much, as fire in the headers will make gobs of heat too and spoil the headers in the process.

With a stock CB radiator lengthened 4", Buick high compression 215, racing cam, 600cfm 4bbl, 1-3/8" fenderwell headers (coated), no sealing around the radiator, ~14" electric puller fan, a good spoiler and low ride height, I could kick on the fan at about 180 and keep it below 210. If I let it get above 210 before kicking it on it wanted to run away given a fair chance and had gotten as high as 240 on one or two occasions.
With a (very) low compression Olds 215 and the same configuration overheating was never a problem.
With the Olds and a turbocharger sitting on the intake manifold, cooling was always a little iffy. After adding a new radiator (5 row brass/copper 4" longer than stock) and a crank driven fan matters were back in hand but it still got uncomfortable in the cockpit in traffic, and fuel in the carb bowl would boil.

My suggestion: put the largest radiator on it you can, and the largest overflow tank you can fit, seal it all up to the bodywork, make sure you have a good fan shroud and move as much air with the fan as possible, but then give that air as natural an escape route as you can live with. For a stock appearance the vent holes mentioned above should be just the trick.
Jim Blackwood

You can make your own foam rubber sealing strips by getting the stuff from any Home Depot and trimming it to suit your needs. As Jim Blackwood suggested, seal the front of the car as well as you can. However, Jim's suggestion about allowing the hot air to exit through the wheelwell area is a real eyebrow raiser. I'm not sure that it would be practical as described on wet roads, though. Perhaps using the fans he mentioned and with the simple addition of fender well liners it could be made practical. Another thing that you might consider is the exhaust system. Sometimes a too-restrictive exhaust system will cause an engine to run hot. Just exactly what exhaust system are you running on that modified engine?

Do you have a reasonably detailed picture of the set up you describe? It might be the answer to a lot of people's problems.
Steve S.

Marc,I cut one hole on each side as large as i could.The holes are against the firewall and above the frame rails so they are out of sight and aren't even noticeable.The holes are rectangular shape but larger on one end.If you look at your B in this location,you will understand how I cut them.I plan on covering them with a stainless louver so it will keep the water out of the engine bay.Jack Emery from the MG Guys told me about this little trick.I haven't really noticed any difference on the temperature gauge but it's gotta help the under hood temperatures.I'm going to install a crank driven fan which Jack also recommended so they should help to exhaust the heat that the extra fan will be pushing.
Ken Blough

Looing at an R V8 yesterday, I say that instead of the mesh fan guard which I have in front of my radiator on top of the fans, they have a solid shield made in some black coloured synthetic material. In addition to guarding the fans, I imagine that a solid guard must also contribute to directing air through the radiator. Standing over my fans I feel a certain amount of air is simply coming upwards and not being pushed through the rad. Off course shrouded fans will help; too but why bother to have a mesh guard when an aluminium one, say, should also help cooling.

Jim, I'm intrigued because you are the first person that I have come accross who says that copper is more efficient than ally. I had always thought that it was the other way round and that's what all of the radiator-related web sites say


Mine runs between 180 and 200 degrees F. The 14" puller fan turns on at 190F. I have a V8 radiator with homemade RV8 style headers. In the middle of May I drove in 95F tempatures through Nebraska to southern Iowa and the tempature guage registered close to 200. On the return trip it was cooler, about 80 to 85, and the car ran between 180 and 190F. In the mountains just west of where I live it goes up to 200 plus when climbing and them cools to 180 when I coast. Going up Loveland Pass it will sometimes go to 210, but cools as I go downhill.

I glued some foam to the hood (bonnet) to block the air flow over the radiator. Tomorrow afternoon I will start driving to Minnesota. I hope it help with the cooling.

See you there.

Al Wulf

Conduction of heat in metals is very similar to conduction of electricity, therefore the most efficient material would be gold, (I'd like to see *that*!) then silver, copper, aluminum, steel, and so on, various alloys falling in between. I would think there could be some combination of alloys that are exceptions but a physicist could answer that question better. I don't know what they would be, but considering there are aluminum/copper based alloys who knows? Manufacturers of aluminum radiators have a vested interest in showing that their product is better, however the facts usually demonstrate that they are lighter, the welded or furnace brazed construction is less prone to leakage at elevated pressures, the materials are less expensive and they are generally preferable for racing applications, but that they are less efficient at conducting heat to the air and less durable long term in street applications. Many claims are made that advanced tube/fin layouts etc give greater efficiencies and this may be so, but advances have been made in brass radiator design as well.

I don't have the photo requested, primarily because my car has evolved beyond stock to the point where my configuration would not be much help. However as for the concern about rain, note that any rain that got in would be trapped inside the chambers formed by the reinforcements and a suitable drain hole would allow an exit. The plastic liners might work just fine with this arrangement, but I think since we are mostly concerned with low speed conditions it is important to allow the air to exit as high in the wheel arch as possible, and not to require it to flow downwards to do so any more than can be avoided.

I will try to look at the car this evening and suggest a more definitive layout, and maybe post a link to a shot of my setup.
Jim Blackwood

Harry, on a chilly 80° day my gauge reads past the mid point of the temperature gauge as long as I keep moving. In stop and go traffic it will get close to the hot mark. On toaster days of about 100° the gauge will rapidly climb to the ¾ mark and go into the red zone at idle. Today it will be over 115° and I know better than to drive it. My four cylinder MGB never went past the N no matter how hot the ambient temperature was.

Jim and Marc, I checked to see which radiator metal transfers heat best and here are some good conductors and some insulators.

Silver 4.173
Copper 3.937
Aluminum 2.165
Brass 70% copper, 30% zinc 1.220

Glass .008
Styrofoam 0.01

As you can see the bigger the number the better the heat transfer ability. You can also see that adding a little zinc to the copper drags the heat transfer ability below aluminum. I couldn’t find anything indicating which metal absorbs or releases heat from water and to air better.
I was surprised by that because the web sites giving information about aluminum radiators stated that brass was better than aluminum in every way except that brass core tubes can only be ½ inch deep and aluminum tubes can be over an inch deep which allows more surface contact area between the core tubes and the fins per inch of radiator thickness (over 1/2 inch of course!) Either way, the final result is that an aluminum radiator has a greater ability to transfer heat from the coolant to the air passing through it.
I really believe my brass radiator could handle the heat produced by the motor because it maintains the temperature at speed, but not at idle. On the other hand, I want to be the first guy on my block with a silver radiator!
George Champion


Good point about vested interests, this may apply to Steward website on Water Wetter- worthwhile checking out redline site.

A high efficiency brass radiator would be ideal but where to get one.

Hood vents seam to be the ideal way to get heat out, but your way does keep the stock look.


Before i did my convercion the first time, cooling was at the top of my reading, every book and manual sugested that at least try to match the size of the radiator that the donnor car had. I have a 1963 Buick Skylark Convertible with the lovely aluminium v8 the size of it's radiator core is 12.5 x 23 giving a surface area of 287.5 in. sq. With this in hand I consulted several radiator catalogs and i found that the ford falcon/ aerly mustang had almost the same dimention in width as the MGB only deeper by about 3in
this dimentios are 16.5 deep x 17.5 width giving a surface area of 288.75 in. sq. now how closer can you get? and this is only a 2 row radiator. I could get a 3 row radiator if need be, but, so far i am pleased with it, that is why i am useing this again in my MGB/Rover. I have RV8 heathers ceramic coated, 2 rows of louvers on hood 11 each 5" wide. I know this is not everybody cup of tea, but, works for me and I love those louvers.

Me again, forgot to tell you guys. my car is a '76 converted to chrome bumpers, ST spoiler, I fabricated an Aluminium scoop or duct that directs all air throug the radiator, mechanical fan, 50/50 solution of coolant, I have used water wetter,but, to be honest i can't tell the difference with or without. I have a little A/c thermometer that i use across the fins of the rad, when tempeture in gauge reads just about 5/8ths of the way to hot the thermometer reads 190 in 80 deg ambient temp in really hot days 95 or better it climbs to 200 or 210, but never boils over, maybe i think we are worring too much about it?

I've had cooling problems (sounds like something from Alco Anon) ever since I fitted a 4.6 unit. Stage 2 with a 214 cam and pushes out around 280bhp. The rear of each head is tapped and take water from here forward into the overflow line and hence into the rad, bypassing the thermostat. Normal out of town driving the temp is about 130-140f even on track days, but hit traffic and the fan holds the temp at 200f but won't cool it down from there until we're on the move again. I.e. an hour in a jam equals a full hour of fan on. Long spells like this make the idle lumpy, possibly due to fuel evaporation. It's got an uprated rad, 14" x 7 blade pusher fan, 20% antifreeze plus water wetter. Bonnet louvres made no noticeable difference though I can see the heat haze pouring out of them when stationary.

I tried the exhaust wrap which seemed to make things worse. Can't see the point of having even hotter metal pressed up against the relatively cooler block. Surely extra heat must be going into the block?

Anyway, since the system appears to be in equilibrium as it is I'm off to have an alu rad made. Will report back on any changes (apart from a lighter wallet obviously).



I must admit running without a thermostat does not sound like a good idea as two low temp can damage engine and warm up is not as quick. My thermostat opens at 180f (I've tried 190f) and I assume optimum operating temp is above this, can anyone confirm as I may be totally wrong.

I agree that exhaust wrap is not a good idea but coating sounds interesting.

Marc's electric WP also seams a good way to go with traffic problems, have you fitted it yet Marc?

The place making up your Alu rad - Can they also make up high efficiency Brass rads?


Good info George. I'm sure the fin/tube makers take it into account. Wonder what tin instead of zinc does?

Anyway, 1/2" is definitely not the limit on brass tube width. The catalogs show sizes well in excess of that, although as the size goes up the wall thickness and tube thickness does too. I think I've seen sizes up to 1-1/4" but don't quote me on that. Any competent radiator shop will have the catalogs for the cores with any tube/fin layout you might want, including folded/louvered fins, flat fins, etc. A little research will go a long way in finding the optimum configuration, and the catalogs should have all the info in the front or back on the merits of each style. Top and bottom tanks can be fabricated from brass stock, or the old tanks can be used.

Getting back to the vents, the brace we were discussing is shaped like an elongated pyramid laid on it's side with the base against the footwell. This junction, on the bottom, makes an excellent location for a couple of drain holes, and about a 1" holesaw should make quick work of it. The top surface is near ideal for a vent if the fenders will be off, but cannot be easily accessed otherwise. Optimally, one hole on top and two on the side sized so as to retain the strength of the brace should work well. I didn't have time to do any layout, but believe the top hole could be 2-1/2 to 3" and the rear side hole could be near that, while the front one was held near 2". If reinforcement is desired, various means are possible, but a 1/4" steel tube such as brake or fuel line bent to fit and welded or brazed into the opening should be quite adequate. Slitting the outside with a .040" abrasive disc would allow the tube to slip over the edge of the sheetmetal first. Of course this presumes that the paint is not completed or that touch-up is acceptable. Otherwise, a formed angle matching the top bend of about .050" sheetmetal could be attached to the top outside corner running front to back.
Jim Blackwood

Jim, I'm having difficulty visualising your vents (if you don't mind me saying so). If there is any chance of a photo or drawing it would be helpful.

George, Thanks for the very informative posting. However, I've alreeady ordered and part paid my ally rad so I suppose, like David, I'll fit it and report back.

Paul, I haven't fitted the pump yet. Frankly I'm having difficulty finding space for it. Talking to some guys who built a succesful racing MGB V8, it's been suggested that the oil filter could but fixed under the front right wheel-arch close to the headlight housing. They also reckon use a Cosworth filter - half the size and very efficient.
If I go down this route then there will be a good space and the pump will go in easily. I'm very curious as to the effect.

On thermostat removal, the same MGB racing guys told me that proper cooling of a V8 depends on some restriction to increase the water pressure so that the coolant is forced round all the cylinders. Apparently the rear cylinders always run hotter than the front ones unless there is some special plumbing which involves running the water route through the core plugs. The thermostat provides the constriction necessary to create the required pressure increase otherwise the lwater takes the lazy route and very little gets to the rear cylinders. Take the thermostat out and you must replace it with a restrictor - typically a metal blanking plate drilled with a 5/8" hole.
This is all new to me. Anyone know anything about this?

Jim, I just found the definition of brass to be 1: an alloy consisting essentially of copper and zinc in variable proportions. Before that I was thinking it was copper and tin. We can only get radiators made from the materials that are available.

What I have read agrees with what you said, brass core tubes can be made deeper than ½ inch, but the additional thickness required becomes impractical.

I have also thought of venting those support wedges you speak of, and even using a heater fan to pump air out through there at idle.

Marc, here’s a picture of the part without the front wing (fender) blocking the view.

Every little bit helps and the aluminum radiator should cool better than brass so it’s good you are getting one. I’ll be glad to hear what you have to say about it. I’m becoming reluctant to spend additional hundreds of dollars to gain a bit here and there.

My oil filter is where you describe near the right headlight and sharing a bolt with the horn on the other side of the panel. It’s a very good place for it, easy to get to, doesn’t drip oil during changes and is one less thing cluttering uyp the engine bay.

George Champion


Perhaps I wasn't clear enough re tapping water from the back of the heads. The usual thermostat remains in place and operates normally. In practice the system takes a small amount of water from an area that would otherwise become very hot due to it being an area of lower flow. The cooling effect is small but results in a more even temperature along the heads. I'm considering using a tube clamp in cool weather to avoid overcooling.

Re engine operating temp, I always thought that should be less then the opening value of the thermostat. Can anyone confirm or deny?

Re brass radiators, I will ask my alu rad guy.

Copper+zinc=yellow brass Copper+tin=red brass, at least basically. All kinds of alloys in between with lots of other metals added in depending on the application. It's surprisingly easy to get a specialized composition. Can't claim to be an expert (ex=has been, spurt=little drip under heavy pressure) but *my* radiator man claims brass radiator cores are more efficient. Starting to sound like a pissing match to me. Go with what you like. Personally I like that polished brass top tank. It goes well with the rest of the brass in my engine bay. Guess I'm just a brassy sort of guy ;) Incidentally, I understand those larger brass tubes are used regularly in truck radiators, so I don't know how impractical they are.

Anyway, I shot some photos just to convey the idea of the vent holes. In the first one you can see the fans I installed, but as they are in what is normally the dead space inside the root of the fender it's not real helpful. In the second shot I've shown some possible hole placements. In the third I've shown some possible drain placements. I don't consider the bottom the best place for vent holes, but if the fenders are staying on it would be the easiest. Lastly, is a shot from the inside showing how the air is to get out, as well as the joint where the drains would be. Now hopefully these links will work right, I'm still a little amazed when they do.
Jim Blackwood

The engine temp is always *higher* than the stat temp because of the time lag in getting heat from the cylinder, through the walls, into the water. It is for this reason that your temp gauge goes up when you switch off because thermo-syphonic circulation, whilst still present to a degree, circulates the water much slower than the pump does. IMHO.

Paul Hunt

This thread was discussed between 26/06/2001 and 05/07/2001

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