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Old 01-16-2012, 12:10 PM
WSBuilder WSBuilder is offline
Join Date: Nov 2006
Location: Azle, TX
Posts: 352
Default Cowling/Engine Truth

The more I ask at Van's the more confused I get. I'm about to order the finish kit and think I want an IO-360 w/ CS. As I understand it, the RV-4 cowl for an IO-320 and an O-360 are the same but this cowling has to be modified to accommodate the IO-360, horizontal induction engine they sell? If so, where can I get the alternate inlet?
Bill Grant, A&P
RV-4: Fuselage controls
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Old 01-16-2012, 01:39 PM
AX-O's Avatar
AX-O AX-O is offline
Join Date: Jun 2005
Location: SoCal
Posts: 2,336

Vans sells it.
RV-4 fastback thread and Pics
VAF 2019 paid VAF 704
The information that I post is just that; information and my own personal experiences. You need to weight out the pros and cons and make up your own mind/decisions. The pictures posted may not show the final stage or configuration. Build at your own risk.
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Old 01-16-2012, 01:41 PM
penguin penguin is offline
Join Date: Jan 2005
Location: England
Posts: 1,063


I think you have to build it yourself. In the old style cowls there wasn't enough room for a filter, the new style cowls are shorter (to accomodate a CS prop) and have a scoop (for a vertical induction engine), but I imagine it will be too low for a horizontal induction motor. You may be able to use the RV-8 snorkel kit, but there may not enough room around the starter? Whichever way my guess is you are in for some glass work.

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Old 01-16-2012, 01:56 PM
WSBuilder WSBuilder is offline
Join Date: Nov 2006
Location: Azle, TX
Posts: 352

Originally Posted by AX-O View Post
So just order the 0-360 cowl and the 3/4 alternate inlet?
Thanks AX!
Bill Grant, A&P
RV-4: Fuselage controls
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Old 01-18-2012, 05:53 PM
Avengerboss Avengerboss is offline
Join Date: Dec 2008
Location: Ramona, Calif.
Posts: 251
Default IO-360 install

So just to be clear you want to install The IO360! Is this the larger head "angle valve" 200hp engine?? I was wondering if that would work or not and has anyone installed the IO360 angle valve in a 4 or not? I put one in my RV8 and that was a tight fit. I'm now building a RV4 and wouldn't mind putting that angle valve in if it fits..
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Old 01-18-2012, 10:06 PM
WSBuilder WSBuilder is offline
Join Date: Nov 2006
Location: Azle, TX
Posts: 352
Default Straight Valve

No, I'm thinking the XIO-360-M1B (180hp) version.
Bill Grant, A&P
RV-4: Fuselage controls
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Old 01-19-2012, 02:59 AM
Andy Hill's Avatar
Andy Hill Andy Hill is offline
Join Date: Dec 2005
Posts: 976

Hi Bill...

As I understand it, the RV-4 cowl for an IO-320 and an O-360 are the same but this cowling has to be modified to accommodate the IO-360, horizontal induction engine they sell?
My take on this...

The RV-4 (and 3/6/9?) are not designed, at the Vans catalog stage, for the Horiz Induction IO system. From Vans Engine Link it states:
The XIO-360-M1B (180hp) and the XIO-360-A1B6 (200hp) use the forward facing oil sump and injector body permitting the use of Van's "horizontal induction" cowl that does NOT require an external scoop on the lower cowl. ALL other engines have a vertical draft sump with fuel injection or carburetor that DOES require the external scoop on the lower cowl as seen on most currently flying RV's, and our RV-9A and IO-540 powered RV-10.
i.e. in Vans terms, Horiz Induction = No Scoop at all, uses Snorkel to get Intake Air from LH Cooling Inlet. In turn, I believe this is only catered for with the RV-7/8(A). For an IO-360 on the RV-4 they expect you will be using a Vertical Induction Injection unit.

As a guide, look at p4 of the RV-4 order form RV-4 order form and you can see the dramatic difference in intake geometry.

Why can I rattle this off so quickly? We are building an RV-3B, and I wish to go the same route with Horiz Induction, as we have on our RV-8 (see Pic. The debate is the next stage:
  1. Try and get a cowl with no scoop?
  2. Is there room for a snorkel arrangement? NB we will not have an alternator up front, so more room, albeit on the RHS with less intake room due cylinder stagger?
  3. Or carry the intake straight forward as on the One Design I have a share in (see Pic )
  4. What exhaust system are you going to use and how will this fit around the Induction / Cowling
Whatever, I think you are going "off piste" with this design (as are we), and you not going to get "off the shelf" parts from Vans, hence maybe the confusion?

Clearly if you progress this any further, I'd be most interested
Andy & Ellie Hill
RV-3B G-HILI very slow build
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Old 07-29-2018, 06:03 AM
chris mitchell chris mitchell is offline
Join Date: Jul 2006
Location: near Harrogate, England
Posts: 380

Reviving an old thread.

I have been pondering how to deal with the cowling issue on my RV-4, given that I have a Lycoming IO-320 with a Superior cold air sump, ie, horizontal induction. I already have a coling from this kits revious incarnation, and a quick search of the Vans website produced:


Well that seems pretty definitive! A modification would be in order.

Step one was to remove the existing scoop. After 10 minutes work with a step drill and jigsaw I had a pretty large hole. I hadn't really appreciated how big the hole was going to be, nor how assymetric the scoop was - presumably a feature needed because of the rotating airflow off the prop?

I thought I would go for a letterbox type scoop, a bit a la P-51D. However, after another 30 minutes sitting, clutching a beer, staring at the cowling and trying to think deeply, I decided I already had a pretty good scoop lying on the workshop floor that just needed to be reattached rather further foward.

After a bit more trimming I was able to locate the scoop in line with the front edge of the cowling, using epoxy thickened with microfibres, colloidal silica, and microballoons as needed, plus some bits of divinyl cell foam. Having got it glued in place I realised that when the prop goes into coarse pitch, the trailing edge of the blades might catch the edge of the scoop. If that happens I will just have to cut back the front of the scoop and make good. Too far gone to retreat!

I'm now working on getting the grafted scoop faired into the cowling and filling the hole left at the back of the cowling (which is about 1 foot square). Again, epoxy/thickeners/foam and glass tape as needed.

So far so good.

But now the burning question is - how do I duct the air from the scoop, via a filter, into the front of the engine? Presumably I need to fabricate the top/inside of the scoop, so as to have somewhere to position the filter and also to attach some ? neoprene?? sleeving that I can the - somehow - attach to the front of the FI servo?

I have seen sugggestions that a filter is not really necessary but I would prefer to have one if at all possible.

I'll add some photos shortly to show what I have done so far. But if anyone else has gone through this process, I'd love to hear from you.


Chris Mitchell

Repeat offender;
RV-8, QB, built, flown 150 hours, sold;
RV-4 - attempted repair, rebuild and remediation - abandoned and junked ;
RV-4 fuselage and wing kits - both at QB stage;
2015-2018 dues paid!
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Old 07-29-2018, 08:30 AM
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Mark33 Mark33 is offline
Join Date: May 2010
Location: Baton Rouge, La.
Posts: 596
Default Sam James air filter housing

Have you looked at the Sam James air filter/housing setup for their horizontal induction cowlings? Their filter housing is "cone" shaped and is designed for a specific K&N filter. You may very well be able to make it work.

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Old 08-02-2018, 09:09 AM
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smokyray smokyray is offline
Join Date: Jan 2005
Location: TX32
Posts: 1,804
Default Holey Cowl

As mentioned above, Van's has made several different cowl iterations for the Ah-Vee-Four over the years.
Initially, the old vinyl-ester cowls most of us original builders dealt with came in two varieties, Fixed Pitch and Constant Speed. The carb air inlet scoops were identical (small) as the FAB, cold air induction, cell phones and VAF for that matter hadn't yet been invented. It was up to us builders to fabricate an air box to effect efficient air induction. The Redneck Ram Air Box I cobbled together in 1994 with primary ram air/alternate K&N filtered air is still working well on my RV4 to this day.

When Van introduced the FAB in the late 1990's, many of us early builders were suspect of the claimed 1" MP loss through a filter versus our Ram air setups. However comma, having now seen the FAB "in action" over the past 20 years I'm a convert, it really works. Later, Vans would introduce the new Pre-Preg fiberglass cowls now standard on all their kits. The RV4 Pre Preg cowls come in 2 varieties as well for the 0-320 and 0-360. This due to the size difference of the FAB for the different induction systems.

As Axel mentioned, Van's sells the bigger scoop for those with older cowls installing an 0-360 or those upgrading from the lower displacement as Chris so eloquently elaborated. You could easily modify an existing cowl for a snorkel arrangement, buy why? It's a 40+ year old design well proven over time. To quote Einstein, "why argue with success?" As far as recommended exhaust configurations, from personal experience helping numerous RV4 builders over the years, I would select the Vetterman 4-pipe arrangement for exhaust.

If you desire an Angle valve IO-360 up front, plan to do some "fitting" to shoehorn it into your FWF.
My Dos Centavos...


Last edited by smokyray : 08-02-2018 at 09:37 AM.
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