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MG MGB GT V8 Factory Originals Technical - Factory V8 rad OK w/big Rover V8?

Will a factory V8 rad cool a big Rover (4.6)? I have looked around and it seems to me that the cheapest and most straightforward solution (as well as the most "correct" looking) is just to use a factory V8 rad (they're about 88 quid at Moss UK). Or is that not up to the job? There's also a unit marketed by Clive Wheatley that's the same exact thing except the core is 4" taller ... so it hangs down lower and holds more water and I guess you have to improvise for the lower hose. Kinda costly though ... worth it?

Anywhere in the USA sell V8 rads at a reasonable price? ... BTW, is a factory V8 unit the same thing as a RB 4-banger's radiator?

In either case - cooling will be critically dependent on airflow so your choice of fans will be more important.

There is more info in archives - the consensus being that one big puller fan is best (if you can get it to fit)

The other related issue is how to keep the engine compartment temperature at an acceptable level - there are lots of answers to this one.

Roger Walker


As soon as I changed to a 4.6 cooling became an issue ,which was not the case with a 3.5. I've had the V8 Rad enlarged by a local firm.(I did consider Aluminium but they are expensive) This has worked even in 2 Hour traffic jams but the final test will be a jam on a hot day.

I'm still using the two yellow fans, but would go with Roger's suggestion if overheating becomes an issue again.

The MG Owners are now selling uprated Rads.


I don't understand the benefit of the Wheatley-style V8 rad that has been vertically extended. I have seen lots of V8s with such a setup, but the bottom just kind of hangs down there in the breeze, and without fans, ducting, etc., I can't see how it would be effective at all. I mean, assuming you're going to run a front sway bar, you're not going to be able to fit a big puller fan over the back anyway ... the sway bar goes right across the rear of the rad ... best you can maybe do is a 13-14" crank-driven fan, which doesn't do squat for the bottom several inches. I was just wondering what the benefit of the vertically extended rads could possibly be ... is it simply that they hold more water?

Like Paul I changed from a 3.5 to a 4.6 and immediately found overheating in traffic a problem. Despite a powerful 14" electric fan and an uprated rad the temp would just keep on climbing. Only the addition of water wetter combined with just 20% antifreeze concentration enabled the temp to top out at around 195. However the fans remain on constantly until the car is moving sufficiently to cool it back to normal.

So, despite the cost, I am having an ally rad made to my spec and should finally give me the luxury of my fans switching off occasionally when stuck in a jam. Marvellous!


The science of water cooling leaves me cold, but there is a very good tech info thread in the the archieves. Certainly volume of water must make a difference and I do know of a chap with a 4.6 Cobra who put such a large Rad in that in now runs too cold. I like David also have Water Wetter in the system but only as a knee jerk reaction when I was using standard V8 Rad. I am also using Block huggers which add to heat under bonnet but the standard fans do switch off in jams.

In case of Global warming, David can you let me know which fan you are using.


The whole "uprated" radiator thing needs, I think, to be taken with a grain of salt. The V8 rad is a brass 3-tube non-offset setup; about the only "uprating" (what a much-abused MG term!) you can do is go to a thicker 4-tube core. Problem is, that exacerbates the difficulty of getting cool air successfully through the rad (cf. misc. hot rodder mags; much discussed), and depending how your car is rigged you may have very little ability to have the backside of the rad moved aft to accommodate a 4-tube core ... you mayn't be able to fit the unit into the car. About all you can easily do is go to a core with offset tubes, but air throughput is a bit harder with that too. Should probably scrap those useless OE yellow fans anyhow, since they seem to have such a devil of a time actually persuading air to go _through_ the rad rather than simply bouncing off it! IME those fans are an un-funny joke!

As per Harry's inquiry above, it does very, very little good to simply have more core area unless there is air passing through it. If it's just hanging down in somewhat calm air below the car, it's not going to do any material, good, and even if the air is moving, it's just going to go around it. It won't hold more than a trifle more water, because the vertical tubes are so slender to begin with.

The key is the fans, and the way the cowling is set up. There are many ways to do it, but the goal is exactly the same: force air to travel _through_ the core. You can use crank-driven fans or electric fans ... or anything else you can think of to force cool air through there.

I have only a crank-driven fan at the moment, but because I don't trust that flex fan behind my rad (seen too many cases of where they have 'flexed' right into the core), I am converting the car to a setup using four 8" electric fans (each of which is 800 cfm, in theory: two pushers on the front (mounted slightly higher than the OE yellow fans' centers) and two pullers in back (mounted down low, just above the anti-roll bar). The back of the rad will be cowled with sheet metal such that the only open area is the fans. The two pullers will stay on all the time; the two pushers will be thermostatically controlled with manual override. The pair of pullers fits on the rear even though my water pump pulley is close to the backside of the rad (standard motor position, w/long-nose water pump) -- each puller fan sits below the c-l of the pulley, and off to the side, so it easily clears. The pushers and pullers will be on independent circuits (relayed, obviously), so that an electrical snafu on either won't cause a meltdown. Additionally, having four fans gives you a good margin of fault tolerance ... I would seriously worry with just one electric fan on there (even if I could get it to fit, which I cannot) because if it goes kaput, that's all she wrote. The only thing I don't like about this system is that when all four are on, the whole thing will draw 22 amps; the car only has a 55A alternator and we'll see if that provides enough oomph with everything else running.

Note that some of the Japanese cars with very, very hot little motors have absolutely diminutive radiators -- almost laughable in some cases -- this is because the designers have ensured that air is forced through every single part.

Clive also sells (or sold, I have one) a 25% uprated rad that is the same physical size. It is better than the standard but the fans still struggle to get the temp down to N when stuck in traffic on a warm day. As always the problem is more about getting the hot air out of the engine bay, but the factory (dual) pusher fans are also chronically inefficient.

Paul Hunt

Paul, do you think that replacing those yellow OE fans with modern 8" electric pusher fans would help? (I realize you have a factory car and so might not be so quick to change out stock equipment ... but I don't have any similar qualms to speak of.) I feel that the yellow fans, without a shroud or anything, basically just spray air in every direction rather than forcing it through the rad. Here in the US, Jeg's sells 8" fans that I believe are each rated as 680cfm when configured as pushers. They have a close-fitting rim/cowl which should work to force air through the rad. The only thing about them that might be questionable is that the motor is about a 4" disk in the middle, and that would absolutely stop airflow. I'm kind of wondering whether it's worth $130 and an hour or so ... do you think they would be an improvement?

(Also, in your other posts you often use the word "pukka" and each time I wonder, what in the devil is he talking about? Please advise!)

from the Oxford Dictionary site
puk-ka ['pVk@] adj. (also pukkah, pucka) Anglo-Ind. 1 genuine. 2 of good quality; reliable (did a pukka job). 3 of full weight. [Hindi pakka cooked, ripe, substantial]

Terry - I think even fans with the 'shroud' attached to the fan tips would be better, the stock fans do indeed pump air all round the outside of the rad, probably becsuse there is as much likelyhood of air being thrown sideways off the tips as forward. I'm still pondering the metalwork and fitting required for a fixed shroud. A single large puller fan would be even better, of course, as used on the RV8.

Note not 'pucker', which refers to something else altogether ...

Paul Hunt

This thread was discussed between 14/06/2001 and 29/06/2001

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