GUIDE : Fitting GTO vents


SM Official Expert: Guide Author
SM Expert
May 26, 2009
Derbyshire, UK
I personally think GTOs are one of the best looking cars on the road. I also think the Supra would benefit from vents to relieve some of the heat build up (especially over the turbo) during a hard run and when the engine is switched off. Two birds with one stone and all that, here's a guide showing you how to fit GTO 'vents' (they aren't really vents on the GTO, purely cosmetic), to a mk3

Note : This isn't a mod for style, it serves a purpose - the positioning of the vents isn't where I'd have picked ideally but they are in the place that (in my opinion) was the best for cooling

Step 1 - Acquire some Mitsubishi GTO/3000GT 'vents'. I got some black ones off ebay for £33 including delivery and the colour match was absolutely fine for my black Supra (although no red flakes on the GTO I'm afraid!).

Picture 1 shows the back (note the four mounting screws), picture 2 shows the front-and the fact they aren't really vents, simply fibreglassed pieces. Picture 3 shows the profile of the vent, they don't interfere with your vision but you can see them when sat in the car.




Step 2 - Place them on the bonnet in a position that suits you. I chose practical usage over style although I would have liked to put them further forward and out to the sides more. Basically, assess whether you want to do this or not!


Step 3 - Remove the plastic retainers for the bonnet heat blanket/sound deadening. They simply pull out although require a bit of force and some will probably snap. Second picture shows you that there are a few (10 ish) to do



Step 4 - There are also two metal clips nearest the bulkhead, simply squeeze them with a pair of pliers and retract them. The second picture shows you the type of clip

Note : I left one of the black plastic retainers in at the front of the car until I'd removed the metal ones to stop it all falling on my head while I did them



Step 5 - The padding should now be free and you can remove it from the car. I didn't refit this but that's up to you

Removing the material under the bonnet for heat dispersion/sound deadening will increase engine noise slightly and there are rumours that it COULD lead to paint blistering/discolouration. I've done this twice and never had an issue but on your head be it. If you do replace it, you obviously will need to cut out a couple of holes to allow the hot air to escape through the vents


Step 6 - Close the bonnet, place the vents in position and start measuring. Do this by eye as well as with the tape measure - spend a lot of time on this bit, don't cock it up or they'll look sh*t!






Step 7 Get some masking tape and slide it under the edges of the vents (The vent will be sitting proud on the mounting screws)


Step 8 - Even though you should have been careful in step 7 not to disturb anything, measure it all again. Second picture shows me checking they were both in line - you get optical illusions where it looks like once is lower etc, the tape measure never lies



Step 9 - Mark out where the vent sits. Due to the fact it sits proud of the surface you could easily have your pencil (pen could dig in to the paintwork) at an angle so be careful to keep it perpendicular to the bonnet


Step 10 - This bit I did by eye rather than measuring. Look under the vent and see where the mounting screws sit. Slide a piece of tape under so it is over the area the screw hits then mark a cross on the tape precisely where it sits



SM Official Expert: Guide Author
SM Expert
May 26, 2009
Derbyshire, UK
Step 11 - Once you've marked out the holes for the front two mounting pillars, remove the vent and grab a drill. Your car should look something like picture 2



Step 12 - Find an appropriately sized drill bit (picture 1). I can't recommend highly enough how important the drill bit type is - get one for cutting metal or prepare to spend a LONG time getting through your thin bonnet. It really makes all the difference

Drill the two holes out and use a screwdriver/hammer to remove the lip which appears on the underside of the bonnet (picture 2)

Important : Make your holes bigger than you need, it will make fitting easier. You will then be able to slide the vent around slightly rather than trying to force it into place and stressing it.



Step 13 - USE WOOD! If you have a couple of people then remove the bonnet to prevent the risk of damagin anything in your engine bay. I was on my own and didn't want to remove it so put a piece of wood under where I was drilling - saved my car several times!


Step 14 - Once you've got your two front holes, use another piece of tape and by eye drop a mark for the third and final hole.

The GTO vents have four pillars and you are drilling three of them. Why? Because they are going to be real vents. By leaving in the pillar at the outermost edge, the vent will be angled upwards so air can escape up the side closest to the centre of the bonnet and at the rear of the vent


Step 15 - Do the same for both sides


Step 16 - Find some nuts (Or request they send the mounting nuts with the vents) and use them to hold the vents in place. If you have cut holes that are far too large then use a washer to hold them in place. Second picture shows mine held in place with 2 bolts (The third one is under the webbing which strengthens the bonnet)



Step 17 - Fit both vents in place (picture 1). You should have a reasonable amount of space at the rear/side of the vent for air to escape (picture 2)



Step 18 - Remove the vents so that you can mark/cut holes for the air to escape. You can either cut by eye or use more masking tape to layout the area you want to cut. I didn't worry about making the cuts neat because the vent will cover it anyway

Obviously you are limited by the area the vent covers (I was surprised how big they were which was good), you've also got to decide whether you want to cut through the webbing on the underside of the bonnet or cut around it. I decided to go for one large hole cutting through the webbing using an angle grinder.



Step 19 - File down the edges of your cuts and then hammerite all bare metal to prevent rust from appearing where you have cut/drilled the bonnet.

There is no wind noise from these at all for which you can thank the aerodynamic shape of the vent. They look good to me and they seem to allow a good amount of air to escape. Due to the fact that air can escape, nasties such as water (Rain/snow) is always going to be a concern. If you angle them like I have I don't think there will be a problem with this but I'll report back if I find any side effects/problems. I am also considering running a bead of sealant around the edges so air can escape but water cannot enter