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James Cowl downdraft carb box install

rockwoodrv9

Well Known Member
Patron
I am trying to get my carb box installed on my James cowl. I am stumped. My only other idea is to go to a muffler shop and have them fabricate a bend to make it work or try glassing something up. Glassing may be easier in the long run.
Here are a couple pictures showing the issue. The front of the air filter is at the height where it needs to be to meet the front of the cowl. If you have pictures or ideas, I would sure love to know what you did to solve this. I know I am not the first person to have the James cowl and this exhaust system. Thanks for the help.
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This one is just a shot of my panel lit up!
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Thanks for the response. I had that photo and I don't believe that is the same exhaust box I have.

I can use SCAT tube to make the bend, but still working on a fix for the carb heat intake. I may have to cut it off the box and move it to the front to allow me to connect it to the air filter tube.

It is always interesting trying to complete a build!
 
Rock, look up the big filter updraft air box Chris Zvatson did on his Lancair.
 
Dan,
I looked up Chris's work. Impressive for sure. I have a great plenum and baffle system I am finishing up now.

With the James cowl, it restricts the air filter to the KN Will supplied with the cowl. Well, I could do major modifications and open up the intake to a larger or even square shape, but that is more than I want to do now.

After speaking with Will and looking at it a bit more, I believe the best option is to use a piece of scat from the carb intake box to the air filter tube. Cut the carb heat fitting from the exhaust muff box, seal the hole, and move it to the front facing surface on the muff. That will allow me to run the SCAT tube and a shut off between the alternator and starter. When I get back to the airport Monday, I will see if that will work.

I had to re-clock the air intake on the muff that goes to the left side cowl inlet to fit around the fuel line. That went pretty well so I hope re-locating the heat outlet will work as well too.

I can't be the first to use a downdraft carb with a James cowl, so not sure why I am having trouble making it work. I have found when it is not going as it should, I am usually the one making the error. I am not sure what it is this time.
 
rockwood,
It looks like you are trying to fit separate systems together with a "one piece fits it all together" solution. Most likely anything cobbled together from unmatching parts won't meet your standard.
The only way I know for you to gracefully do this is to Make something yourself to fit the front (cowling) and the aft (carb) to fit an air filter and any other required components.
It's worth $10 in foam and a nice 6 pack to cobble something together in a couple nights and see what if????? Odds are you'll scrap the first model but the small investment will steer you onto the path to completion.
Happy building!
 
Dan, I looked up Chris's work. Impressive for sure. I have a great plenum and baffle system I am finishing up now.

I'm not talking about a cooling plenum. Follow the link Kyle posted for you. The large flat filter has far more media area than the little cone filter you're trying to use. Free power.
 
I have never liked how the transition from horizontal to vertical looks so when I installed mine, I modified the FAB.

Here is a picture of my solution.

Notice how the FAB now angles upward towards the cowl opening and that I had to make a custom flapper for the carb heat.

It seems to work very well.
 
My alt air heater is much smaller than yours, but still required something to link the filter housing to the intake snout. I used a short (3" to 4") piece of scat tube with clamps to do it. Mine is similar, though not identical, to Radomir's pic. I'd post a picture, but I'm not presently at home where I have access to the photos.
 
I'm not talking about a cooling plenum. Follow the link Kyle posted for you. The large flat filter has far more media area than the little cone filter you're trying to use. Free power.

I understand about you were not talking about the plenum. I just don't believe I can fit a rectangular box in the space provided in the cowl inlet area. His article was very interesting in how he was able to get 10 more hp jus from that change.

I am all for me power and will look at the space again and pick up a kn filter that will fit. It could be a fun project to work on after I get flying. Now I just want to get done and in the air!

Thanks for the help.
 
I may have a solution. I bought a plastic water bottle and did some cutting. I plan to make a mold like the photo and build a transition piece out of fiberglass and see if that works. I can get the cowl on and off as is, so I think it should work.
IMG_5461_zpsj5b97zo1.jpg
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I should be able to put my carb heat door in reasonable easy and it should give good heat at that point.

Can anyone see a problem with this plan?
 
Im still working on my James cowl with a downdraft carb and heat muff in front. I have been unable to make the James supplied air box so I am working with the Vans FAB. I have things clecoed together and unsure on a couple things.

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The cowling - plenum - FAB has been difficult for me to get done. The glassing - I am fine with, but not understanding the whole baffling - engine cooling - carb air needs, has stumped me and caused me grief!!

Thanks.
 
carb heat

I believe you are missing the carb heat box that needs to be grafted onto the air filter housing. PM me your email and I will send you pictures of my install.
 
FAB install

It is hard to see the transition piece from the SCAT tube to the FAB, but it is there. In the first picture you can see it clecoed to the FAB. I have not built the door - flap yet. Once I get everything figured out, I will put the door in.

My question is do I need to worry about how much air gets in through the front of the air box?

If I push the glass cover up to make it tight to the air filter, it makes the box very narrow.
I can make a ring to allow a deeper box if that is the way others have done it.
I have searched for pictures and haven't found any with the setup I have. I can't believe I am the first person to use a long James cowl with the heat muff up front on a carb engine.

Thanks for the help.
 
Sorry for my ignorance, I don't have an updraft Lyc, but what filter are you using in this FAB? It looks circular from your first photo above, but maybe it's not?
 
Sorry for my ignorance, I don't have an updraft Lyc, but what filter are you using in this FAB? It looks circular from your first photo above, but maybe it's not?

In the photo with the Vans FAB, it is the round filter that comes with the kit. I have the complete kit from Will James that has the cone shaped filter.
 
IMHO, I would stick with the SJ setup you started with above but add his alternate air/carb heat option.

Also see pic on next to last page of this SJ instruction.

Im not sure what way to go here. For me, the Vans FAB fits the best and appears to be the strongest structurally. It fits OK and Im sure I can make it work by machining a ring forcing the round filter tight to the glass housing. The only issue I see is without the making the ring, the inlet is too small and restricts the air to the carb too much and would reduce power.

The cone James filter that I tried to make work with the blue plastic bottle, there is no way to put a flapper door for the carb heat. I would have to make this modification to the heat muff.
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I have talked to everyone from Larry Vetterman, Clint from Vetterman, Will James, and several builders from the Boise area.

At this point, I think I will make the flap door using the Vans FAB, make a ring or some way to force the filter tight to the glass housing and still allowing plenty of intake air and see how it works. If that works, great.

One other option I just thought of so I could use the James cone filter is to abandon the existing carb heat outlet from the muff and plate off the opening. Buy a new muff and put it in a different location with an outlet just for the carb heat. That would allow more room to get the SCAT tube to an acceptable location so I can install a flapper.

What an ordeal! Thanks for the comments.
 
One other option I just thought of so I could use the James cone filter is to abandon the existing carb heat outlet from the muff and plate off the opening. Buy a new muff and put it in a different location with an outlet just for the carb heat. That would allow more room to get the SCAT tube to an acceptable location so I can install a flapper.

That would be my recommendation as well (heat muff on one pipe for carb, another for cabin heat - remove the dual pipe muff) but it's an opinion and you know what those are worth :D
 
That would be my recommendation as well (heat muff on one pipe for carb, another for cabin heat - remove the dual pipe muff) but it's an opinion and you know what those are worth :D

After seeing more pics of your heat muff, I too think this is the way to go. The heat muff I have for carb heat is waaaaay smaller than the LARGE one you show. As such, the connection to the SJ cone inlet is quite straightforward with a short length of scat tube.
Also keeping in mind that if you have FI, the likelihood of needing carb heat - or alt air - is significantly reduced. Methinks it would not be advisable to have a less-than-optimal combustion air intake for the sake of a seldom-used alt air inlet. In four years of flying, the only time I use the alt air and flapper door is to test it about twice a year.
 
In the end, it may be easiest to just have FI installed. I don't want to take the time for that now, but it is looking like a good option.

I was not going to install the ALT air flap at all. Im not sure what advantage it would be over having a carb heat door. If things are going that bad, Im landing wherever I am anyway!
 
I used a chunk of silicone tubing prefabbed at 45degrees after the SCAT kept ripping. No issues since...
 
In the end, it may be easiest to just have FI installed. I don't want to take the time for that now, but it is looking like a good option.
I was not going to install the ALT air flap at all. Im not sure what advantage it would be over having a carb heat door. If things are going that bad, Im landing wherever I am anyway!

On my SJ intake setup, pulling the alt air knob automatically gives carb heat, I.e. the alt air intake location IS the carb heat muff. I believe it was designed that way to warm the air filter surface in the event it freezes over.
 
James Induction on 0-360

What I did. Silicone 45 degree fitting from internet, trimmed down. Scat hose failed.
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On my SJ intake setup, pulling the alt air knob automatically gives carb heat, I.e. the alt air intake location IS the carb heat muff. I believe it was designed that way to warm the air filter surface in the event it freezes over.

That's what I thought is how the James cowl intake works.
I am finishing up the Vans FAB construction and will try to install it tomorrow to see if it all fits.

I plan to order a piece of silicone tube with a 45 degree bend so I can put together the James intake system and see if I can make it work too. If I can make it fit with the exhaust I have, I will seal off the existing heat outlet from the muff and get a new muff to get a different heat source for the carb heat -alt air source.

Thanks Terry.
 
What I did. Silicone 45 degree fitting from internet, trimmed down. Scat hose failed.
UVPaxDDUW3wpOVQkX0wtZIxJbEcY8nLuUj84ioKAN-OnzzGeTs0yM2estA6HuPlhbyYOznoFJKndYijPFuZPKDx5ntE1u9qUef9gDiEsxB5L1EtUT0KalRpXjWtVzZQ6mXR394NZyKu6KKoYFN3zvS8YtC2i7iwz4eYJE4JxL5dtMc1gnb-Pb9W4tMkg6Fw4-CGRc_f9MfBWTFGr1D5FuhD9beMaMuR09PQqQ_rEMj3zrq11z1PvgIJTMCeJXU5ch9AP3R0PNx4WMlTI2kVOvyFnH91P2vAn2wRxig11RxDunDQAoaUVnWids3JEhG4u2dcgkDqd31QAMtnIDKw02LbmHU32JOZcXzuvf_WM9csfLTdgW7khc96zK29gb2Lpq7tEiMeg2wZ-J_2sgKioCkgzr8r_S7gnWMW-faqRtsbDa3rPu95GsThS_GsOyCcCZz6WbCaUuXdrwZ7rNisJZqW60uzbkGZ42kwLWPfE05pDwmxMqSUsrE9HaMyx0ig2b_nxC2YVaiV0P2NSjuWOVH_UbTPN0yivpVSUWgiu0VRDjt6LcQ1njLWD5cOgC-kfLiot19NMZBkujAPtSHHCV5gNptI_VXoRH7KnUAkX3UmsSWi1TPru=w640-h480-no

I have been pondering building my own FAB after flying the Vans FAB for 200 hours, I appreciate your work and pics. I'm not sure that that setup has any alternate air at all, if the air filter gets
plugged the engine quits. I think alternate air should bypass the filter altogether.

It also seems to pinch down and constrict airflow shortly after the filter. What about a wider body from carb to filter with an alternate air provision like N91CZ?

11E5D474-6E76-461B-AFD3-CB88594B97BF_zpscqdzzd5r.jpg


Again just bouncing ideas around until I tear mine apart again, I seem to make everything a bigger project than it needs to be.
 
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wow nice work

Crabandy, I enjoy and respect your glass work and "can do" attitude.
That airbox on N91CZ is a piece of work, nicely done. Craftsmanship for sure. Assuming this accomplishes a couple things. No appearance of a restriction in air flow from narrowed passage and carb heat on inlet side of filter in case of restriction, therefore the carb heat is the Alternate air. And possibly more airflow through a larger air filter media than the James K&N unit.
I have looked hard at the James fiberglass transition piece that connects the filter to the carb bottom. The side view looks narrowed which it is, top to bottom, but it does widen out to compensate. This version was not Will James's first crack at this and I had to assume he did careful calculations on flow. It appears proper to me in my hand.
Alternate air is another topic. I am VFR only. I pondered the risk and obviously decided it was one I could/would take. That said, the bottom of the transition piece would be an easy target location to install a rotating door with a little glass work as there is ample clearance under it to the cowling.
Pondering here with my thoughts about the induction in general. I looked at a lot of posts here from very creative people. I had lived with a standard Vans air box for hundreds of hours and many condition inspections and repairs. I also learned about the importance of the design and how it came about. Cliff notes here: Vans originally used ram air on the 3 and 4. Once Vans figured out he had a winner of a design and the intake could be a problem he set out to design an intake that would not hurt performance over a ram air setup. Understanding this made me realize the importance of sealing the intake system from leakage both at the nose connection and at the carb heat door while closed. Vans had used the Pressure recovery process of enlarging the air box for the filter media and sized the box for good airflow thru it.
That said I could not see a good transition from the vans air box to the round intake ring of the James Cowling, that I was installing. But I could see Will James had figured it out. I proceeded to build the carb heat flapper door the best I could as far as sealing went and really liked the neoprene seal at the nose better than the Vans baffle material set up.
So, like you....I just did it.....time will tell how it holds up!
I converted from a standard Van Cowl to a James long cowl and plenum and induction system...plus a new paint job. I did not do before and after documentation but had lots of hours flying it. It now is several MPH faster in cruise.
So to quote Tom Cruise from Top Gun..."it is looking good so far";)
YMMV.
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