Larry Foster Fox .35 mods Flight test

It doesn't happen often in the Texas panhandle this time of year but today was a wonderful day to fly. Marvin Denny is in Amarillo for family reasons but had a free afternoon. He brought with him a "Foster" Fox .35 and Gary Minor, Don MacPherson and I met him at the field in Amarillo. Would you believe Marvin didn't have a plane for a Fox .35? Well, I happened to have a PDQ Super Clown that is fit for that engine so I took it to the field and Marvin and Gary bolted it on.

All of us flew the plane and were amazed at the difference in vibration. I am not an engine man so I can't get too technical but Marvin will probably have more to say about this when he gets back to Wichita. Marvin asked me to post a rave review about the way this engine runs. Very smooth with lots of power. This was the first time the engine had been run so power may improve with a little time but as is,with only 6 flights on it, it has a bunch. Kudus Larry!

Larry has my Fox 35 right now, and when I get it back, I just know it's gonna make the winter seem longer, just waiting till the weather gets good enough I can take it out and try it. I'm really looking forward to it!

Tim

I put my L&J Fox 35 (it's ready to go now) in my Argus tonight.
This weekend *might* be a flyable one, and if so it will finally get into the air!
Can't wait.
Bill <><

Supposed to get up to 43 tomorrow. Can't remember if that was the temperature or the wind speed. Ah, well, flying weather will come soon enough

Len,
Temp. here in Kaysville Utah will be in the high`s 28 deg.But the real problem is the two feet of snow in my yard. Just finishing my new Classic needs three coats of clear. Then wait for the snow to melt.Hope I get to test fly it before VSC in Tucson.

Gordie

>Len,
>Temp. here in Kaysville Utah will be in the high`s 28
>deg.But the real problem is the two feet of snow in my yard.
>Just finishing my new Classic needs three coats of clear.
>Then wait for the snow to melt.Hope I get to test fly it
>before VSC in Tucson.
>
>Gordie

Gordie:
It was 69 here today, almost no wind, Nice and sunny T-Shirt weather.

Larry

Any information as to whether the "new" Foxes (with the HZ crank) will eliminate "THE BURP" when side mounted? Let's hear from you all. I spoke to Randy the other night about this and from his design changes, it seems that the new crank, Back plate, etc. might help...

It is my understanding that Larry's Fox 35s do not burp on outsides when mounted on a profile, but that is a function of his filling and reshaping the bypass port. Plus (maybe) the stuffer back door.

I don't think the crank, whether stock, modified by Larry, the High Zoot crank from Randy has much, if anything, to do with it.

>Any information as to whether the "new" Foxes (with the HZ
>crank) will eliminate "THE BURP" when side mounted? Let's
>hear from you all. I spoke to Randy the other night about
>this and from his design changes, it seems that the new
>crank, Back plate, etc. might help...
>
>Ward

Ward:
The reduction of the Fox BuRp is done by filling in the By-Pass port and reshaping it in a pattern that the Old OS Max 35 used. Narrow at the crank end and wider at the intake port. I do this by taking a dremel tool and scribing the case, then etching it with Acetone. I fill in the port with enough JB weld (NO 5 Minute) to level the port with the edge at the bottom end. To get the JB Weld to flow I use a heat gun and allow it to flow to each corner. Then I take a dremel sanding drum and reshape the port. The key is to see the case metal again at the top of the port. I've done this on over 800 motors with no problems. The non Fox Hemi-Heads help this problem too, because of the plug location.

Larry

I don't think I've done anywhere near 800 but have done a bunch by just inserting a piece of spruce in the bypass. About 1/4 x 1/8 carved to fit seems to do it. Not quite as elegant as the JB weld but works great nonetheless. All we are really trying to do is increase the flow to keep the fuel mixture from condensing on the wall of the case during an outside maneuver, right? I'm not really trying to start an argument here just trying to point out the wood method is easier. I recently de-gummed some engines that were in the attic for the last 30 years and discovered the wood was still ok and the engines still performed as before.

LAST EDITED ON Feb-12-04 AT 09:36 AM (CDT)
 
Tom,
I am just guessing that most customers would prefer the JB Weld over the chunk of wood in their professionally reworked engines!

LAST EDITED ON Feb-12-04 AT 05:22 PM (CDT)
 
You betcha,

If I paid to have an engine reworked I would want it done that way too. All the wood does is cure the "burp" and a lot less expensive than going the entire "hizoot" route (poetic eh).

Not all engine seem to need this fix but it dosn't hurt either. I fly a lot of .35s on booger profiles so I add it when I obtain a new engine. Some of the flea market engines already have the mod installed. Bring the piston to the bottom and look before you mod one. I always thought most control line people knew about this. But there I go think'n again.

Thanks John.

You're welcome Larry.

FYI guys: Super Clown is a profile. NO BURP anywhere in the pattern. Gary Minor Chicken Hopper tank.

A request to Larry Foster and Tperry2054. Some of us more inexperienced types are having trouble visualizing the descriptions of bypass modification to stop the "Fox burp". Would it be possible to post some pictures on this thread to show what the parts look like after the work is done. I am very interested in both the JB Weld method and the spruce wood methods...........Thanks for any illustrations you can provide...TD

Terrance,
No pictures but *my* understanding of the process.
You want to reduce the size of the bypass to increase velocity of air/fuel mixture. I know Larry does the full blown reshaping of the bypass, but the "stick" method was just an older way of reducing the volume of the bypass. A stick stuck vertically in the bypass relived so that the cylinder will fit in the case. About 1/8th thick by 1/4 wide.
Bill <><

It's not real handy for me to get to my engines right now and I don't really want to pull apart an engine. What you should do is disassemble your engine and have a look. Take a piece of spruce 1/8 x 1/4 x couple of inches long and shape to fit in the bypass just hold the piece in place and trim until you can put the liner back in and it is held snugly in place by the cylinder liner. If you have to force the liner back in it is too tight. If you screw one up just do another. All you are trying to accomplish here is to make the total bypass volume smaller thereby increasing the velocity of the fuel mixture to the cylinder. All we are doing here is keeping the mixture from condensing on the surface of the case. Remember that this is not needed on a non-profile model, but it won't hurt anything either. I have never noticed any difference in power out one way or the other, the mod just cures the "burp" on outside maneuvers.

>A request to Larry Foster and Tperry2054. Some of us more
>inexperienced types are having trouble visualizing the
>descriptions of bypass modification to stop the "Fox burp".
>Would it be possible to post some pictures on this thread to
>show what the parts look like after the work is done. I am
>very interested in both the JB Weld method and the spruce
>wood methods...........Thanks for any illustrations you can
>provide...TD

What I will do is consult Mr Lucky Pyatt on taking some photos. On engines I'm reworking at this time. Working 12 hours a day right now so no promises on this.

Larry