Which parts should I delete from my Van’s order if I order your kit?

You may delete all items related to the cowl, plenum/baffles. Useful items in common will be the rivets or fasteners used to join the hinges to the cowl, and the hinges or fasteners used to join the cowl to the firewall.

When ordering the extended cowls, you may also delete the filter air box if planning to use our ram air filtration system.

All “standard length” cowls (RV-4 and short version 6,7,9) use Vans FAB filter system.

We recommend a different mil spec hinge along the cowl sides: 1-1/4” hinge (MS20257P5-3) on the bottom and 3/4” hinge (MS20257P4-3) on the top half of cowl. Hinge required is one three foot section of each type. The lower hinge is riveted to the cowl with the flat section exposed above the fiberglass side edge. This allows the top cowl half to overlap the bottom hinge, thereby eliminating the “saw tooth” gap.

How much work is it to install your cowling/plenum as compared to a Van’s installation?

For the cowling, the work necessary is same as the Van’s installation except for the additional time required to mount the aluminum rings.
For the plenum, flat stock aluminum pieces must be cut and bent. Directions, diagrams and photos are included.

I may be building an RV-8 using the engine from my Mustang II. Can I also use the plenum?

The same plenum is used for all aircraft, they only vary with engine size. For more information about the plenums please contact Will James 850-342-9929.

Will the wheel pants fit on other aircraft?

We have wheel pant sizes for use with 600×5, 500×5, 500×4 and 340/300×500 tires. For more information please contact Sam.

Can I use your plenum with my Van’s cowling?

Our plenum will fit under the stock Van’s cowl. The issue is connecting and sealing
Vans inlets to the plenum. We can provide fiberglass inlets and rings that may be “grafted in” for some of Vans cowls. Difficulty and results depend upon skill and enthusiasm.

Is the protrusion seen in the middle of the middle of the 200 hp plenum photo a mod done by the owner for the spider?

Associated Items

What are the dimensions on the rings?

X-Large Ring OD “6.00 ID: 5-7/16

Large Ring: OD 5-1/4 ID 4-5/8

Medium Ring: OD 4-3/8 ID 3-3/4

Small Ring: OD 3-3/4 ID 2-7/8


Which size rings do I need?

Cowlings are designed top use specific rings that area provided with each cowl design. For separate ring purchase, call / email for casual advice, will : 850-342-9929

What is included with cowl kit?

2 Cowl halves
Oil inspection door
3 Aluminum inlet rings
Neoprene Rubber
Seal Cement
Fiberglass cloth
Cotton flock thickener

What other items will I need?

Flat stock aluminum (alternate air system) approximate size 5″x8″ – 0.032” thick
Flat stock aluminum (engine plenum) approximate size 3’x3′ – 0.035″ thick
Aluminum duct tape
Mill Spec 20257-5 piano hinge for lower half of cowl, (1) 3’ lengths (on 4 cyl. engines)
Mill Spec 20257-4 piano hinge for upper half of cowl, (1) 3’ lengths (on 4 cyl. engines)
Hinges for firewall attachment (as per Van’s instructions)
Rivets (as per Van’s Instructions)
Skybolt Fasteners (if used)
Mold release wax (good quality car wax will do)
West System Epoxy or equivalent (Do Not Use 1:1 mixtures)
K&N model E-0995 air filter (available at Advance Auto Parts, Autozone, CarQuest)
2” scat tube (for alternate air inlet nozzle connection to heat muff)
12” length of 3” scat hose

What kind of air filter do I need?

K&N Filter E-0995 or KA-1000 (available from James Aircraft for $55 or local auto parts stores)

What kind of fasteners should I use?

If you plan to use fasteners to attach the cowl, we prefer Skybolt Fasteners. These have a very nice appearance and are micro adjustable. They are of the finest quality and many feel are worth the extra expense.

Where can I get the fairing filler material you recommend?

We recommend AwlFair. Follow the links at their website to find distributors in your area. For pinholes, be certain to use an epoxy based filler.

Where can I get the Plastolene clay  mentioned in “Fiberglass 101?”

Plastolene clear clay is available from Suncoast Polygard at 800-282-9498


Who do you ship with?

For foreign and domestic shipping we use a freight broker which guarantees low prices with our frequent shipper discount. When parts are ready, freight costs will be paid directly to freight carrier. Pre- shipment estimates available on request. Smaller parts may go USPS or UPS with postage costs added at time of initial payment for the parts.

How much will it cost to ship a cowling?

Usually, there are a number of different options: dock pick-up,residential delivery, or commercial delivery to a business address. Dock pick up and commercial delivery are roughly the same price and run approximately $70-$75 less than residential delivery. Shipping estimates can be provided on request. Plenums and wheel pants ship for a $35.00 flat rate to all domestic addresses.

Do you ship internationally?

Orders may be shipped worldwide via sea or air. Estimates available upon request. Overseas shipping is expensive. Picking up your shipment from port of entry (or personally arranging transfer to your address) can mean substantial savings. You can of course request door to door delivery bearing the added cost in mind. We will work with you to provide any service desired.What payments do you accept?

Payment in U.S.D. can be made by wire transfer, paper checks, Western Union, etc.

Propellers and Extensions

Do I have to use a prop extension?

We offer three different cowl versions for the RV-6/7/9:

1) The standard length (shorty cowl : (34-5/8″ length) for carbureted or updraft fuel injected engines uses the same propeller/extension combinations as for standard Van’s cowling.
This cowling uses Van’s filtered air box.

2) The extended length: (37″) for carbureted or updraft fuel injected engines

3) The extended length: (37″) for forward facing fuel injected engines and updraft,
require either an extended “M” hub propeller (or equivalent), or the “CY2R”hub with a 2-1/2” extension.
For all fixed pitch metal or wooden propellers a4″ extension is required.

All cowl measurements are taken from the firewall to the prop spinner ring and include trim area.

Where can I get a prop extension?

Please contact Saber Manufacturing on the web or call 817-326-6293.

What size prop spinner do I need?

All horizontally opposed engine cowlings use the standard Van’s spinner.

What propeller should I use?

The extended length cowlings were designed for the “M” hub (extended hub) propeller. However, any wooden or metal prop may be used with our cowling along with a propeller/extension combination correctly sized to equal 6.75″ from the hub center line to the mounting flange. View prop diagram here.

Some of the newer broad chord props like the Hartzell RB-74, may have contact issues with the cowl inlets, Stand props like the RV series, Catto, etc work fine.

Materials and Quality

How well do your cowling halves fit together?

Our cowling halves fit correctly and should require no bending or re-shaping. They will have to be trimed at the sides and firewall for length

What material and construction technique is used with your cowl?

The cowl material is a woven cored composite comparable to “Nomex Honeycomb” in terms of strength and rigidity but without the paper core. The cowls are generally easier to finish than some but expect to fill some pinholes. This newer material also results in a cowling that is lighter than our previous hand layup. The resin used is vinylester, which is non-warping, and heat and chemical resistant.

This material may be used for rotary cowls provided specifications for length of core, oil and inspection doors can be provided by the builder. Otherwise, the RV-4 and rotary cowls will be constructed as a “flat-glass” and vinylester layup.


How do I place an order for a cowl or filter system?

Please contact us by phone (850-342-9929) or e-mail (will@jamesaircraft.com) at the North shop. Please include specific information with regard to aircraft type, engine type (size and sump orientation) and type of fuel injector servo or carburetor. Please include phone number and e-mail address with order. Please make full payment at the time an order is placed. We will generally ship a cowling within about thirty days after receiving a check, although wait can sometimes be twice that, depending upon demand. Foreign orders may require longer lead times due to shipping arrangements.

How do I order wheel pants, or parts made at the South Shop?

For orders within the US, please contact Sam at the South Shop. He is not on-line, but can be reached at 863-675-4493. For foreign orders, please contact Sam directly, or Will at the North Shop through e-mail: will@jamesaircraft.com
Parts from the South Shop are generally shipped within 30 days of receiving a check except during summer break, June- July.