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MG MGB GT V8 Factory Originals Technical - Vent Holes in Inner Fender/Wing

While my engine is out of the car for rebuild,
I'd like to install some air circulation holes into my inner fenderwell.

Does anyone have any pictures or can direct me to photos on the web that would give some ideas on how others have done this?

Thanks again for the help,


I would suggest that if you are going to vent your inner wing then you should put the holes where you would have to cut if you had decided to go ahead and install RV8 headers. As you are just fititng vents you might not wish to cut as large holes as you would for RV8 but at least if you decded to go the RV8 route at some time you wouldn't have to worry about weaking the inner wing anyfurther because of your vent elsewhere in the inner wing. On the other hand you might want to cut vents as large as RV8 ones and in that case the reinforcement frmaes are available ready made.
An added bonus to the cutting of vents at the RV8 header position is that access to your block huggers and your start motor becomes a breeze (pun intended).

I'm in process of doing exactly that...I have the holes for my RV8 headers but am also using the rectangular holes the factory put up in the top rear of the inner cutting holes in ther backside of the trumpets & then building vents in the top portion of my fiberglass fenders for the air to exit...
...then, just scroll down to the red square & click on 'garage' to go to the section where i'm talking about my V8'll find photos 7 write-up there as I go along...

...Mike Cook put louvers low in his inner fenders where the RV8 headers would've gone & built vents in the lower part of his outer fenders...
anthony barnhill

I also am in the process of trying to get rid of some that Rover 3.5 V8 heat from my 74 MGB
If you look on the drivers side inner fender up by the brake proportioning valve there is a fairly large flat area. (And a corresponding one on the passengers side of the car as well). I have made a template of this area and will get some louvers punched into a piece of sheet metal and then cut out the existing metal and weld the louvers in.

Marc speaks sense, also Anthonys site is pretty cool, lots of inovative ideas and you'll enjoy his style I think, however I blanch at cutting holes in the outer guards as wellas the inner. Cutting great big holes in the inner was traumatic enough for me. I've adopted more conservative approach (just call me "old Yella") and removed the tops of the splash guards that cover that dead space between the footwells and the outer guard. I then drilled lots of holes into that space at the top of the engine compartment. This gives you a hidden vent from the top of the engine compartment (where the heat is)into the wheel arches. Not my idea, appologies to the inovator, I read it on this site somewhere.
Mind you, although the day draws nearer, I have yet to get this thing on the road yet and how well this will work is all theory.

I'm having a difficult time visualizing where the holes are that are being discussed.

Is there any pictures out there?

I went to Tony's site and can see how the RV8 headers go through the fender well, but I'm having a difficult time with the other descriptions.

I'm using block-hugger headers and just had them coated so I probably won't be going to RV8 headers, but I like the idea of cutting the hole for them, using it for cooling and having them there for a future upgrade.

More detail with pictures?


Phil...go to my site & look at #3 on 14 the upper rear of the driver inner fender there are 2 rectangular holes that open to the 'trumpet' section; on the passenger side, there's only one...I'm cutting a second one on the passenger side to match the driver side...then, I'm cutting 2 3" holes in each of my 'trumpets' to allow air forced into the rectangular holes in the inner fenders to be pulled into the cavity between the inner & outer fenders....than, I'm putting louvers (vents) in my fiberglass fenders so that trapped air can be pulled out of the car....sorry, the URL didn't work
< 14 October 2002>
....Mike Cook made up a small vent down right to the rear of where the RV8 headers usually go to pull air out into the cavity between his inner & outer fenders; then he installed some vents in his fenders
....others are talking aobut making a small vent to go where the RV8 header hole would normally be located...that would pull air out into the wheel well opening...I'm concerned that the the difference in air flows in that space might not do what one wanted...i.e., it might push the hot air back into the engine compartment
anthony barnhill

The hidden vent approach,
These are vents at the top of and extreme back of the engine compartment, in addition to the usual RV8 style holes. They can't be seen because they are at the back of the small space to the side of the pedal box (and also passenger side). If you follow the Hood release cable you'll end up in the right area. They vent into what once was a dead space. I just drilled lots of half inch holes in a regular pattern
Visual aid:
If you were to imagine removing the front guard, Starting from the front of the car you would then be looking at the front bumper, the wheel with the wheel arch behind it (where I and others have cut RV8 style header holes) and just before the doors, the outside of the foot wells. With the guard on, there is a dead space between the guard and the outside of the foot wells, often the radio arial projects into this space.
Essentially I (and others) have made a vent from the top of the engine compartment into this space and then made a vent from this space into the wheel arch by removing the top of the splashguard. I prefer this approach because I rather like the idea of a V8 MGB that looks completely standard, rather like Clark Kent.....then... super car! (it's all very physiological I'm sure).
Also the wheel arches are low pressure areas.
Note though, I suspect that this will only have a marginal effect compared to the header exits, but it's very easy to do and can't be seen so I though, why not?
It should also keep this dead space (normally a rust trap) dryer than usual.

From what I can gather, (correct me if I'm wrong Automan) Anthony is going straight through the outside of the guards, not into the wheel arches. Going for the "James Bond Aston Martin" look I suspect, which does have a certain attraction I'll admit.


I don't understand what you guys are saying -- if you fill the cavity just outboard of your legs with 200 degree air ... your legs will just absolutely cook.

Peter...yep, you're right...007!
Savid...My plan dumps the hot air outside the car body at the high ends of the inner fenders & through the outher fenders...
...if you dump air low, you'll end up in the dead air space inside the wheel well....the air flowing along the side of the fender above the trim line will effectively pull the hotter air out of the fender through the vents (I hope!)
anthony barnhill

Your car is an,.....M......MG..... (base guitar goes crazy)

It is confusing unless you are looking at the car. We are not actually running the exhaust into the area hereafter known as the "Footwell/guard dead space". The headers/extractors go out through the inner guards regular RV8 style. We are looking at additional vents for the top of the engine compartment where warm air collects. Warm but not 200 deg!. There is insulation for the footwell in the form of trim pannels, and if temperature becomes an issue I can always easily add more insulation, or close over the vents.

Peter....funny you should mention the Aston Martin...I've been looking at the various fender vents available to determine the style I want to use...Cobra came to mind first, then Corvette, some Pontiacs, BMW, Ferrari...&, Aston Martin! A simple teardrop shaped hole cut into the outer fender with a small, elegant chrome spear through its center...hmmmm, that really looks nice &, because my vent will be up along where the side trim should go (yes, I'm removing that also) it might just fenders are fiberglass so I could contour the shape...several cars could lend the small pieces of chrome
anthony barnhill

Should look good,the only fault I can find with J.B.'s Aston Martin is the roof.
Ever noticed (if you ignore the chrome) that the front of an Aston Martin (DB6 ?)looks alot like an MG, which came first I wonder?

This thread was discussed between 19/10/2002 and 24/10/2002

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