Fox 35 hemi head

[Warren Leadbeatter]

Hi all,

I finally got around to installing a Marvin Deny Fox Hemi head and stuffer backplate on my 50th anniversary Fox 35.

Haven't flown it yet... What sort of performance improvement should I expect to see?  I'm running a Topflite 10x6 prop, model is a 57 Nobler, weight 40 oz.  Should I expect it to rev harder and if so, should I put a 10x5 prop on perhaps?

Regards
Warren

[Brian Massey]

Wish I knew, but I sure love your plane.

Brian

[Bootlegger]

   Warren, I have been running an APC 10x5 prop on my Fox engines with the same setup, plus the ceramic liner and alum piston and they and I seem to like it very well.
   Try it and see what you think..

[Jim Kraft]

I would sure try a 10-5 APC, as they work very well on upright or inverted Foxes set up like yours. I have never had much luck running them on profiles, and usually go with a 10-6.

[Jim Thomerson]

I am running an 11 x 5 Taipan. I still run the stuffer backplate, but I took the hemihead off because the engine was just overpowering the airplane.  However, on a larger, heavier airplane, it might be just the thing.  I'd also suggest you try an 11 x 5 prop and see what you think. 

[Warren Leadbeatter]

Tried the model out today with the Hemi Head.  I think it likes the standard head better.  Seems to run better on standard head.  No noticeable difference in power, just ran rougher. Maybe I did something wrong???

[john e. holliday]

I too have tried the hemi-head and stuffer back plate on my Fox's.  They are back in stock form again.  Maybe I didn't have them broke in enough as I may try it again.

[Clancy Arnold]

Warren
I have one on a Barnstormer and it is NOT for sale.  It was such an improvement that I will not take it off the plane until I do a figure 9 with it or something similar.  The engine was barely broke in, looked new inside and out even though it was a very early engine.  It does not have muffler mounting ears or threaded holes above and below the exhaust.

The real trick in installing the head is to be sure the piston baffle is centered in the clearance slot.  If it is not centered it can cause run problems as it can actually be dragging on the piston.  

I would suggest that you try it again and be absolutely sure you have the piston baffle centered in the slot.  There is not much room for error but it can be done.  Turn the button one way until it touches the baffle.  Then turn the button the opposite direction until it just touches the baffle again.  Now back it up half way between the two positions and the baffle should be centered in the slot.
Clancy

[Bill Heher]

What Clancy said, and you can use a fine point Sharpie to mark the limits, makes it easy to split the difference then.

[Warren Leadbeatter]

I was pretty sure I had it right. I used a pencil to mark the line and I had 2 shims, then I changed to 1 shim. I also tried a couple of different plugs. Thunderbolt 4 stroke and Fox Miracle. Fuel is 29% castor, 10% nitro.  I have a Randy Smith one here, I might give that a go and see what it does.

[Randy Cuberly]

I am running an 11 x 5 Taipan. I still run the stuffer backplate, but I took the hemihead off because the engine was just overpowering the airplane. 

A Fox 35 overpowering an airplane...now that's really funny!!!    

Randy Cuberly