Step 7: Baffles & Plenum

Sam provides drawings with his plenum for the aluminum baffles that go along the sides of the engine. I opted to use Van's baffling kit. It was an extra $200 but a big time saver I think. Sam's drawings don't appear to be exact and even have some errors on them. The baffles are essentially the same but Van's comes pre-formed. The following assumes you have Van's baffles and aren't making your own.

First step is to fit the side and rear baffles to the engine per Van's instructions. Do not trim the top edges at this point! Just get the baffles installed along the sides and back. (On the back baffles, you do not need to install the support bracket at the top center.) The tops of the baffles will have to be trimmed, so just cleco the baffles together until after they are trimmed, then rivet as necessary. (Do not install the scat connections yet)

With the sides and back baffles installed, you can start playing with the plenum itself. Sand around the outside edges of the plenum to remove any excess flash material where it will rest against the aluminum baffles. Make sure your plug wires are in place.

Place the plenum in place. I think the object here is to get the plenum as low and close as possible to the engine without interfering with the spark plugs. I think there are some comments in the instructions about removing the ferrel on the spark plug wires to help clear. This doesn't sound like a good idea to me. There is plenty of room to leave the plenum sit high enough to provide adequate clearance for the plugs/wires.

I spent a good 3 hours trimming the plenum along the front edge where it goes around the engine case. My D2J has some large pads on it that required some major surgery on the front left side to get to fit.

Once the plenum has been trimmed as necessary, put it in place and get it level. You should put the lower cowl in place so you can line up the inlet holes with the cowl cutouts. Once you have the plenum positioned, use a marker to draw around the plenum on the inside of the aluminum baffles.

Remove the plenum and baffles. Trim baffles on the line you marked. I recommend leaving the baffles stick up just a bit above the plenum to give plenty of edge clearance for the holes you drill for the screws. (DO NOT USE the template provided to trim the baffles, it will not leave you enough material to work with.)

Position the baffles back in place on the engine.

Locate and mark the location for the 2" scat tube connection on the back right baffle for the cabin heat muff. Make sure it doesn't interfere with your oil dipstick.

Decide whether you want to mount the oil cooler on the back baffle or on the firewall. The firewall option might be better and easier, however, rumor has it that it doesn't perform as well on the firewall. Jury is still out on this as I haven't flown with the setup yet. (I chose firewall) Once you make your choice, install either the 3" scat connection or mount the oil cooler on the back baffle.

Place the plenum back in position. Drill holes for #8 screws/nutplates around the perimeter. I put 4 on each side and 6 along the back edge.

Remove baffles/plenum, install nutplates and scat connections.

Next is the front inlet ramps. I also spent a lot of time trying to figure out the front inlet ramps and how they tie to the plenum. The pictures in the instructions aren't quite detailed enough to show how the baffles/plenum tie together on the front.

Make up and install the inlet ramps along the front of the cylinders per Van's instructions. You will have to rebend/reshape/trim the inlet ramps themselves to match the plenum. I also trimmed some of the lower angled portion of the plenum. This area is challenging.

I have uploaded some photo's to the image gallery here.