How to make your own designer Radiator Grill

How to make your own Radiator Grill
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To make your own grill you will need the following tools and bits and pieces.

A piece of aluminium the width and length of the mouth in the front bumper, 720mm x 130mm x 2.5 mm thick. (Too thin and it will be difficult to work with) Obtainable from any one who works with aluminium sheet, eg Caravan repairers, or horsebox and cattle trailer manufactures.

It should cost about £5.00 (try to get your supplier to sell you a piece without any or very few light scratches on it.)

An electric drill and drill bits 6mm and 2mm, 2” wide masking tape, a jig saw preferably with a saw blade for cutting aluminium, two 6mm x 50mm long hexagon headed bolts, two 6mm a 25mm hex bolts, two dozen 6mm washers, two 6mm dome headed nuts, Two pieces of 20mm x 50mm x 6mm aluminium or steel would do, a 6mm tap and wrench.

The drawing below will give you an idea of the shape of the grill for Mk1 cars and possibly for Mk2 cars too.


If you use the drawing for the two fixing brackets it would be a good idea to make these first, as they will determine the position of the grill. Mine is set quite a bit foreword of the original grill.


Initially it would be advisable to cut the grill outline shape from a piece of stiff card to make sure that it matches the mouth of your car. This can then be fitted onto the bolts attached to the two brackets. Make sure that the outside edge is clear of the mouth by about 4mm all the way round so that if it vibrates it will not scratch the paintwork of the mouth.



The above picture shows where the grill bolts and brackets fit. The lower bolt head may need grinding back a little to give just enough adjustment of the bracket to fit the two holes in the grill, as shown in the grill drawing. The bracket is fastened to the car using the existing tapped holes that were used to fasten an original grill to.
If you are satisfied with your card template you could use this to transfer the shape to the aluminium sheet. Before you do this, cover the best face of the aluminium with strips of the masking tape so that it is covered all over. Now you can transfer the shape onto the masking tape with a pencil. The two most important holes to drill are the two holes that are used to fit over the two bolts on the two brackets. These two holes want to be about 7mm dia, just enough to give a small amount of clearance for the 6mm bolts.

The next thing to do is to draw your design onto the central part of the grill. When you have done this you will then have to mark on horizontal pencil lines where all the holes are to be drilled that will allow air thro’ to your radiator. The holes I drilled were 6mm dia. and spaced at 11mm x 11mm horizontally and vertically. Try to make the lines of holes balanced on either side of your design and also above and below it. (Take a look at my grill to see what I mean.)
When all the above is done you then have to cut the design out with the jig saw and drill all the holes carefully. I found that using a new 2mm, gold coloured, drill it was quite easy, if using a drill stand, to just mark the centre of the holes sufficiently to act as a guide for the larger diameter drill. If you don’t mark the centre this way then you will need mark the centres with a small centre punch. You will also find that you should file the burred edge on the back of the grill where you have drilled the holes.

If you can, chamfer all the holes as it makes the grill look better.

The final cut is to cut the outside shape of the grill.

Then it is a case of filing and making smooth all sharp edges with files and P500 wet & dry papers.

When all this is completed remove all the masking tape, and check that the grill fits your brackets etc and doesn’t catch the paintwork.

If the front of the grill is not scratched at all you can use any aluminium polish to get a good finish on it.

If it is scratched you will need to use P1000 and P1500 wet & dry paper wrapped around a joiners cork-sanding block to improve the finish. 



This is one of many pictures of grills I have posted on the forums.




you need to get out more but another great idea!!!

You may be right but at my age and at this time of the year, all I want to do is keep warm and free from colds etc.[:D]

That’ll help me a lot with the fitting of my designer grille in a few weeks time

Hi -halli-, If you send me your address, again, I will make you a couple of the brackets for you so you can fit your grill at the Tech day. I have more time than you but, you will have to drill two holes in your grill to the dimensions given on the grill drawing for my brackets to work.

Send your address by normal Email as the PM on here messes my Outlook Express up.   

 Email sent
Thank you very, very much.

  -halli-   They are in the post today.  I have modified them a little from the drawing in this thread so the Hexagon headed bolt doesn’t have to be ground  at all. It isn’t there.


 Just a word of caution - virtually all of the cooling air which passes over the radiator has to enter through the 'mouth. It does seem to me that this particular design of grill may seriously restrict airflow. Whilst that may be fine in cold weather (maybe that’s all the time in the North East! [:D]), in warm weather I think you may be in trouble. Sometimes on long uphill autoroute climbs in France in hot (over 30 deg C) conditions I have had to flip the headlights up to get extra cooling. 
 So try this out by all means, but keep a close eye on your temperature guage and be aware that the guage may not move very much when your coolant (and engine) is getting dangerously warm - it is not a very sensitive instrument in standard form.
 And be aware too that overheating is nearly always fatal to the cylinder head gasket - sooner or later.
 I much prefer an open mesh type of grill.

 Perhaps I should just add - this particular ‘John’ is John Cookson, aka Dr Bob.
 And here’s the official bit:
John Cookson
ex -Technical Coordinator (now CMT member ‘Member Benefits’) , MX-5 Owners Club
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Any work you do, or have done, to your car or a car not owned by you as a result of reliance of this information is entirely your responsibility. You should check technical advice with an independent source, and take local specialist advice from a qualified person who has actually seen your car if in any doubt. The MX-5 OWNERS CLUB and its officers can accept NO RESPONSIBILITY for any damage caused to your person, car, property, or third party as a result of following or not following any procedure or advice given in this article.
* * * * * * * * * * * * * *

I don’t disagree with any of the above, I had to make adjustments when I made the first one as I found that the radiator was over heating  so I took it off and tried to see if I could get it to over heat on a long hill climb without the grill on, and yes it did. The fault was with the radiator, at about 15 years old, so I fitted a new radiator and tried to see if the new one would overheat with the first grill I ever made, that had the club twig logo cut out of it

It was fine after fitting the new radiator. The last design that I have is the Tyne Tees Club Logo cut out of the grill and it is fine also. A lot of course depends on the size of the logo, and any surrounding holes, that you would cut out of the grill.

The gaps caused by the design of the Tyne Tees bridge logo are quite large and will a lot of air thro’ and all the holes are quite large too. 

This is the one with the club logo on it, not anywhere near as large as the TT logo and it was fine.




My grille isn’t going to be on full time. It is envisaged it will be for photos, high days and holidays only. My home made mesh grille will be staying behind the new grille. 
The new one is only held on by two bolts, easy to put on and take off.