Installation Of Snap Vents (Windows)

This mod is for the installation of “Snap Vents”. These vents were used on the 66 Le Mans cars as well as other years but they are best known on the #2 winning MKII of 1966. They are actually windows designed for use on experimental aircraft but can be found on many general aviation and helicopter aircraft. They are easy to install but you MUST have the right tools or you will destroy your windows. Also be very careful handling the windows. They are Lexan and can flex quite a bit but they can break if you are careless and they scratch VERY easily. Thanks to Mike Gelb for the use of the REMGRIT saw.

Snap Vents are available from the manufacturer or from aviation supply stores on the Web like Lockwood aviation Supply. The cost is about $15/pr with shipping extra.

The first order is to do the layout. This is somewhat subjective but after a fair amount of research I have determined where I “think” they should go.

With the window removed and on a soft clean cloth on the bench, measure 11 inches from the lower front corner and 4 inches up from the bottom. Where the two points intersect, make a mark with an awl or other sharp object.

It is a good idea to put masking tape all over the area where you will be making the hole to prevent scratches as the hole saw rotates. Use a 3 ¼ inch REMGRIT hole saw. These are not cheap but it is the ONLY way to get a clean cut in this material. DO NOT try to use a regular “tooth” type hole saw. The results will be disastrous and will likely ruin a very expensive window. It's best to cut part way through then finish it from the other side.

Also note that this MUST BE DONE ON A DRILL PRESS. There is no way to use a hand drill and get a clean smooth hole. I've included a lot of warnings here but take it from someone who has done all these things wrong in the past; you'll be sorry (like I was) if you don't heed my advice.

************************* YOU HAVE BEEN WARNED ************************

As shown below, use a large piece of wood to lay the window on. You may also place a cloth around the outside edge of the wood or put tape on the corners. This will prevent scratches as you press the window down with the hole saw. The window is not flat, but being Lexan, it will go flat as you bring the press down. DO NOT put a rag under where the hole saw will punch through. The saw will “pick it up” and get it spinning, horribly scratching the window. Again, use tape for this. Use as slow a cutting speed as you press will allow. When done, use fine sand paper to clean up the edge as necessary being very careful not to scratch around the edge of the hole.

Before you insert the vents, remove the wire bale. It makes it easier to install. I run the vents under warm water to “heat” them up a bit making them softer to get through the hole. Reinstall the bale and you are done.
 

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Pat

Supporter
A note of thanks to Lynn for posting this "How to" and appreciation for the forum's search feature.
I just finished installing a set of snap vents in the '40 following his instructions. It was (as they say) "a snap". The only variation I made was to install a ring of nylon grommet edging along inside of the hole in the window LEXAN just to be sure I don't get any leaks should our Florida weather turn into "liquid sunshine". It also makes for a snug fit for the vent's positioning options. The vent cools the car and really clears out the heat when it's been sitting in the sun.

Here is a photo of the complete installation and what the edging looks like.
 

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Pat

Supporter
Hi Scott,

I purchased the helicopter vents at Wicks Aircraft supply:

Item # SV-CC3251, Retractable Snap Vent On Wicks Aircraft Supply

And the grommet edge at Pegasus Racing:

https://www.pegasusautoracing.com/productselection.asp?Product=4309

To cover my bases, I bought both the 4309 medium and the 4345 large sizes for my 1/8 inch window thickness and found the 4309 a tighter and a better fit and used that.
Also note the Remgrit hole saw has an outer grit that's a few thousandths larger than 1/4inch which is fine if you're using the edging (I still had to do a little sanding to get it the right size) but if you are going without the edging, there will be some play when the vent is mounted. The instructions with the vents recommended a 3 1/4 metal cutting hole saw with 6 teeth per inch or better which if you didn't want to use the edging would be the way to go. However, in my opinion, it would leak.
If you are in the Orlando area traveling and want to borrow the hole saw or take a look at the scraps of the material, just send me a PM.
 
When I had CAV 082 I felt this was one of the best "mods" I made to the car. The extra air into the cabin was a God send. They look great Lynn and Pat.
 
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