47-15 -> 20: Fitting the Snorkle / Alternate Air Door

Fitting of the snorkle was a little bit 'off piste' - the snorkle i purchased was designed for the IO-360 horizontal induction engines, and needed some modification to fit the SDS EFI throttle body, which essentially involved fibreglassing an 2.5" aluminium flange to the end of the snorkle, so it would interface with the SDS throttle body using a piece of supplied silicone hose. 

So I was basically able to follow the standard plans, however instead of drilling and bolting the flange of the snorkle to the throttle body, i needed to first work out the length of silicone hose required to place the throttle body end of the snorkle in the same position in space as it would have been had it been bolted to the FM150 throttle body. 

This was an interesting task, as at one end i had the snorkle floating in the air filter frame, and at the other, it was floating in space! 

I worked out that the FM150 throttle body is 5.5" long. So i figred that i could loosely place the snorkle into the throttle body at one end, then measure back 5.5" from the sump. This would then give me the required length of silicone hose. Easy! (edit: if doing this again, i would also need to allow the the thickness of the mounting gasket, which i forgot - luckily the hose is forgiving of measurement errors!)

A Problem

But then i ran into a little (albeit expected) problem - the lug on the starter was contacting the snorkle and not allowing it to align with the throttle body. 

It was expected that this lug would cause an issue. 

She no line up!

Fortunately, the Skytec Data Sheet for the 149NL starter says:

So i borrowed a high-power die grinder and a cut off wheel, which went through the boss like a boss. 

It's just a $2500 starter! All good!

I also discovered that Skytec had included a couple of extra shear (roll) pins glued to the underside of the starter with hot glue - I decided they were safe to leave there are 'in field' repair parts should the starter shear pin ever shear.

With the boss gone to the scrap bin, the snorkle aligned with the throttle body and i was able to align the snorkle at the 5.5" point back from the sump, then measure how long the silicone hose needed to be. 

'Boss B' did not need to be trimmed. 

I purchased these 66-76mm black hose clamps to secure the silicone hose to the throttle body and the snorkle. They unfortunately have a 10mm nut, but cheaper than buying an aviation part.

Drilling the Snorkle and setting the position

Once the lower end of the snorkle was in position, i could go back to the plans and match drill the snorkle to the air filter frame in the baffle. These holes are simply to keep things aligned during the glue up. 

Since the air filter needs to fit down into this frame, i marked a line and trimmed the snorkle so it did not protrude up too high. I used a light to trace where the bottom of the air filter sat, then transferred this to the snorkle for trimming. 

If left untrmmed, the snorkle would prevent the air filter from fitting all the way down into the filter frame.

The air filter depth was marked using a light.

The cut line was transferred to the snorkle.

At home, i trimmed the snorkle using my japanese thin kerf saw. I was then able to make up a mix of epoxy and flox, and join the snorkle to the air filter frame.

I cleaned up as much of the squeezed out flox as i could, as this stuff is pretty hard to sand.

Alternate Air Door

Next up was fitting the alternate air door. This started by cutting a hole in the side of the snorkle.

Chain-drilled a hole

I was thinking of trimming this flange down, but could not work out a safe way to to do - so left it was it was. 

The air door mounting plate was prepared as per the instructions, including dimpling for flush rivets. For some reason the plate is both glued and riveted on (??). The plans call for a -08D nutplate for the air door pivot point - i had left all my nutplates at the engine shop, so used a -10 nutplate (10-32) i had laying about (and upsized the pivot hole in the frame and the door to 3/16" accordingly). 

The plate was scuffed up on the underside ready to be glued on, as was the snorkle. One hole in the air filter frame was countersunk to accept the dimple in the plate. A larger hole was drilled in the snorkle at the hinge point for the nutplate body to sink into to - the other holes kind of 'float' above the snorkle (held up by the nutplate attach rivets of the hinge point) - these end up being bedded in flox. It's a weird way to do it, but thats the way Van's wanted it! 

I also covered the air door and attach screw in boe-lube wax, and mounted the door in in place to make sure the air door frame was glued on flat. 

The 'body' of this nutplte protrudes through the snorkle, while the nutplate rivets sit on the snorkle itself. This lends the frame to 'float' and it is bedded in place with flox. 

The top tab was bent over to accept the door - the door had to be slightly trimmed to clear this tab and work properly. 

Here you can see how the body of the nutplate protrudes through the snorkle and the nutplate attach rivets sit against the snorkle. This lets the air door frame 'float' and necessitates the flox.

The body of the nutplate showing through the snorkle (with the bolt). These were covered in boelube to stop the epoxy sticking to them.

Once prepared, the air door was glued on with flox. 

Once again, i cleaned off as much as i could to limit the sanding later.

Once cured, the rivet holes are drilled out and the dimples cleaned of any epoxy. The frame is then riveted on. My squeezer had no way of fitting into the hole, so i needed to use the gun and the bar - this was an awful way to do it. The pressure of the gun cracked some of the epoxy - i figured since the main strength here is the rivets, i could use some CA glue along the cracks. Hopefully this holds up ok. 

For anyone coming after me, i think a better solution would be to forego the rivets, and just glue the air door on. The dimples could have been filled with epoxy and flox, then sanded flush and i think it would have had sufficient strength. The dimples act like a sort of 'glued on rivet'. In any case, the rivets have been installed. 

A crack in the epoxy.

Painting

Once the air door was complete, i masked off the areas i didn't want painted including where the silicone hose attaches to the snorkle, around the air filter (so is any paint flakes or wears off it won't go through the engine), and also the mating surfaces between the alternate air door and it's frame plate.  I scuffed the whole snorkle with sandpaper until the sheen was gone. It was then blown off, cleaned with Iso and painted. I used some VHT Plastic Paint in silver as this can withstand up to 200F (93c) - silver was the closest color to match the blue-silver of the baffles (once they are finally painted). 

Expensive hearing aid

The air door was painted on the outside with VHT silver blue - the same as the baffles will be. Hardware was installed. Instead of the called out #8 screw, i am using an AN3 (10-32) bolt. 

The #2 intake tube was fairly close to the snorkle - we will check this is not touching after the engine runs - some tape may be in order here.

I actually installed the snorkle, before reading ahead and realising it needed a #19 drain hole. I didn't want to drill this hole in-situ (attached to the throttle body), so had to remove the snorkle once again, drill the hole, then put the snorkle back on. 

This shows the final fit of the snorkle.