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MG MGB GT V8 Factory Originals Technical - Bonnet louvres


Does anyone know where i can get some bonnet louvres here in the UK, i am going to have to get rid of some of heat in the engine bay.

Graham Lavis

Hi, I had my Louvres done in Kent by a company called Protomotive. Details as follows. Mine was done about 7 years ago. PROTOMOTIVE ENGINEERING UNIT 1 PATTENDEN LANE MARDEN TONBRIDGE TN129QS

Ian Sanders

Hi Sports car metal works are regularly at classic shows. They will louvre your bonnet while you wait by appointment. Duttons Farm. Bangors Road South. IVERS Bucks. SL0 0AY 01753 654144. I have no connection with tjhis company. Just seen their stand and exhibits. Jim
j soutar

You are better off making RV8 holes in the inner guards. Making those holes for the RV8 was a stroke of genius.
The large area around the wheels is a low pressure zone and the hot air just rushes out of there. Even if you don't have RV8 headers the air still blows past your block huggers increasing the cooling effect.
The easiest way to cut them is from the wheel side. The metal is quite soft and a hacksaw blade does the job easily.

Nothing ever splashes up through there (I've tested this out on muddy roads). The flow of air is too strong.
Cutting the holes does not in any way weaken the car. The RV8 uses a weld on surround that is more cosmetic than anything. You can buy these from Clive wheatley

I went around the edge of the hole a few times and turned the lip down a little which looks quite good. Many don't bother and some just use some door edge trim.
I've seen a couple of cars with block huggers that have put vents there. One of them had put in some stainless wire mesh and a stainless surround just for the look of it. Some sort of bathroom fitting I believe.

The area in front of your windscreen is a high pressure zone so vents in the back half of the bonnet aren't going to do much at anything except very low speed. However many people just like the look of it so thats as good a reason as any!

When you are out on the open road at a nice speed, you will [generally] not have any cooling problems.

The problems will kick in during the one day summer we have, sitting in a gridlocked city where you will sit and watch the needle creep up near and into the red. The RV8 seemed to cope, but we hear very little of high mileage ones, and I wonder if they coped after a decade of crud build up in engine and rad.
The idea of louvres is to cope with the stationary idle situation, to allow the hot air which will rise, out into atmosphere.

Cool Louvres are the best. They press them while you wait at a fiver per louvre. There are many opinions on exactly where louvres are positioned.

It depends also on what you are cooling. An engine on its own might not be a problem. I have the engine, airconditioning and an automatic gearbox to cool, and all that with a PAS pump blocking a good portion of my rad!

If you are worried about stationary cooling and your body is in a raw state - an idea I had after painting the wretched car was to have two computer rack fans up at the back of the inner wings, ducted out to atmosphere through the lower rear of the wing, with the outlet dressed with a chrome grille. I do not know if this will interfere with the louvre flow or not. Until it is done, I will not know!
H Adams

I've never had the remotest problem with over heating.
Even on 45 degree summer days in heavy traffic. The car that is, personally I usually feel allot like a fried egg.

The electric fan switches on and off a little more often mind.You can sometimes actually see shimmering heat plumes coming out of the top of the wheel arches. This is a large close coupled/ducted fan, not those fairly pointless MGBGTV8 fans. You might consider fitting two close coupled fans, one on the front and one on the back, opposite corners. It is amazing how resistant air is to crossing the heat gradient of the radiator. A while back a bit of the ducting at the top came away leaving a small one by 20 cm gap. The fan was on roughly twice as often and for far longer.


Hi Guys

Thanks for your input, does anyone have a template drawing for these RV8 inner wing exhaust cut outs? or a drawing or picture of what they put in for letting out the heat, the idea of a mesh cover sounds the way forward. I am trying to keep the outside pretty standard, mind you the exhaust does give it away a bit!!

Graham Lavis

Here's a look at the holes I have. From the top side.

Kelly Combes

And, from the bottom. I welded a 3/16" rod around the edge to form a rolled lip.

Kelly Combes

Clive Wheatley can sell you the original part surrounds (that link above) thereís a photo of them. So expensive that many make their own.

If you arenít using the original surrounds then anything will do.

These next look a lot like mine except I belled or turned down the lip of the hole to make it very stiff. I used a small shifting spanner with a bit of rubber in it so as not to put creases in the metal. There is probably a special tool you can buy.

There are lots of variations on that britishV8 site. Look in the how it was done area,
Peter Sherman

Here's one of my answers to overheating. The louvers are from old discarded school lockers. As well, I'm using a high capacity radiator and large electric puller fan. All incoming air is ducted through the radiator as well.

Phil O

If you look at my car on the V8 list you can see I made very large holes because my headers are big and long 1-3/4 in diam, no restrictions on engine breathing.I did this so I can remove the headers without removing the engine.I have put close to 40K miles on this car and between the louvers, ceramic coated headers, big alum rad, 2800 cfm pusher fan and large cooling holes the car will run in any weather or traffic without heating up.
Gil Price

Graham, you my not be aware that unless you've got the later rubber bumper /V8 inner guards, the Clive Wheatley RV8 surrounds aren't going to fit very well. You can see the shape with Simons car very clearly because of that very nice shiny paintwork. By the way, as far as I can tell these RV8 surrounds appear to be only about 2mm thick, you can see the edge of one on that RV8. cosmetic.
I think that Gil has proved pretty conclusively that no strengthening is required!
Peter Sherman

How do you guys with hood (bonnet) louvers deal with water getting into the engine bay?
Dan Masters


I have got the later rubber bumper car, i don't intend paying £70 for RV8 exhaust surrounds, i have got a hugger exhaust fitted, so there is a reasonable ammount of space to utilise. I intend to fabricate something.

For those that have done this, did you completly remove the under wing cowl, or did you just cut out some of the cowl where required?

Graham Lavis

I just took off the front wheel, drew the shape I wanted, made a starter cut with an angle grinder (drilling a large hole would have done), then continued it with a hacksaw blade. With one of those cheap plastic handles. There's plenty of room to work from the wheel side.

Since you are free to make whatever hole you like, you'll notice that there is already a pressed oval shape in that panel. Just above the rear crossmember bolt. You can see it particularly well in Phil's photo. I had forgotten about it. With some careful cutting & filing you might be able to take advantage of that neat already "belled" shape. Just a little paint on the raw edge and you'll be done.
It might be a bit small, but there's an easy answer to that!

Heres one where Barrie's just made some neat round holes
Peter Sherman

If it rains --and it does --the water collects wherever, just on start up you get clouds of steam for a minute or two and then it dries up quickly. I have had no ill effects from rain --splashing up is not an issue to me as it has never caused problems. You have seen my car Dan and no ill effects to your wiring kit either :-).
Gil Price

I forgot to add my cutouts were done with a plasma cutter free hand to a rough sketch made on the panels.
Gil Price

water entering compartment is probably not a concern due to air exiting while under way. the purpose of the hole is to exit hot air, water should not enter due to negative pressure in wheel well. my holes are not as large (3/8 to 1/2") but do allow some air to escape. my temp. runs rather high (210+) when in traffic, but cools down under way.
BTY, Gil, soak up some sun for all us experiencing winter. hope to see you in Wisc.
kelly stevenson

"Cool Louvres are the best. They press them while you wait at a fiver per louvre. There are many opinions on exactly where louvres are positioned."

They can press them wherever you want with out removing body parts?

I wonder if anybody here in the States offer this service?
Carl Floyd

......a couple of points.....
Be prepared to fork out money for a complete paint respray of the hood/bonnet in the event of adding louvres to one already painted - been there, done that!
From personal experience, water ingestion has been really minimal (w/hood louvres) and has not been an issue.
Adding louvres is more than just elimination of engine heat - it also allows venting of high pressure engine bay air which really helps cooling fan performance.
....and finally, anybody that chooses to spend Winter in Manila, rather than enjoying the cold and snow in upstate New York, is a coward (but a smart one!)
Graham Creswick

Is that pressed squarish oval shape (just above the rear crossmember bolt, Phil's photo) present on Chrome bumper bumper cars?
It is placed exactly where a vent should be and the inner fender of the rubber bumper was reshaped because of the V8.
Peter Sherman

hey Graham
I just wanted to witness a few coup attempts here as it seems to be a national sport! Actually Im not in Manila but away from the crowds in a northern area LaUnion where the beaches are nice and grass skirts in abundance.
Good to see Kelly back at it too !!
Enjoy the winter see you in the summer
Happy Holidays
Gil Price

Re the picture of my car. The cooling holes are the ones at the rear of the engine bay. RH side ones not visible. The prominent holes in the centre are to get access to the Spax damper mounting bolts.I dished the inner fender walls a little too much to gain access from the wheelarch. Barrie Egerton
Barrie Egerton
scroll down a ways. he's done exactly as you intend Graham.

and to answer my own question, yes they were
Peter Sherman


Thats just what i want to do, thanks for that. Wonder if they were custom made or off the shelf somewhere?

Graham Lavis

Almost certainly adapted from something. Looks a little like a drain cover.
Possible donor candidates could be found from,
Cooking utensils, Bathroom fittings, speaker grill, ventilator cover (as in household heater). some sort of toy. Caravan vents etc
Certainly yacht fitting chandlers will have something suitable in 316 grade stainless, cockpit drains for example. It would look great, however boat bits aren't cheap.

I'd go for a bit of a prowl around a big hardware/plumbing shop, or shopping center, home ware for example.

You may even be able to get something in an auto shop.
Peter Sherman

Peter wrote: "I think that Gil has proved pretty conclusively that no strengthening is required!"

It may be true that no strengthening is required, but it's a Monday morning and I'm feeling ornery. Please forgive me for pointing out that little things like crashworthiness may (or may not) be compromised.

Graham wrote: "Adding louvres is more than just elimination of engine heat - it also allows venting of high pressure engine bay air which really helps cooling fan performance"

I think this is true at moderate speeds (40 or 45mph?), but when I tested at 60mph I found that hood louvers need to be pretty far forward on the bonnet to work in the way described. Air pressure gets rather high in front of the windshield at speed. If the louvers are back toward the cowl end of the bonnet, they'll cause decreased airflow through the radiator. Happily, few of us have cooling issues at highway speeds. If someone does... venting the inner fenders or venting the hood right behind the radiator would be more effective.

Some of the measurements I made are buried in this article:

I am with Curtis, tests on aerodynamics have prooved it but louvres look very sporty althoug opening up the inner wings to the low presure area behind the front wheels is a more effective solution.
When driving in normal stop&go traffic, louvres help to control the temperature of the engine compartment but they spoil the look of a B for my opinion. If the fuel line is routed with care, there will be no problems on most of the cars using 4 bbl carbs, otherwise an engine room blower (as even used on x1/9 Fiats) would help to keep the temperature in a reasonable range.
As most conversions have upgraded power outputs, compared to the works cars, it helps a lot to use a ram air box in front of the radiator and also to direct fresh air to the air cleaner. The radiator can be mounted that way, fresh air is passing its sides and then directed to the carb.
On my V8 conversion (finished in 1984) i fabricated the now so called RV8 header and also an air cleaner as used on the Chrysler Hemi cars. Later i changed to a 3" Pancake K&N Filter as to get rit of the large air pipes on each side of the radiator.
Crusing temp is ~84 C, driving through heavy traffic it does not exeed ~95 C.
On my car, i use two puller vents behind the radiator, a 78C thermostate and a Kenlow type switch set to ~85C.
There are no louvres stamped into the bonnet and the engine is good for 184 RWHP.
So think twice, has anything (not noticable from outside) been done to control the temperatur around the engine? Do not rely upon the way Abingdon fitted the Radiator to the works V8, this Stock BGTV8 engine was running at a very low CR, far off it's potential!
Their solution was the best for production, not for conversion!
BTW, when Sunbeam was on the way of pre production test of the Tigre, they also tried louvres on the bonnet, it did not solve the Problem of overheating the engine compartementthat as much as right gearing did.


This thread was discussed between 26/11/2007 and 03/12/2007

MG MGB GT V8 Factory Originals Technical index

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