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Cox Engine of The Month
July-2024
robot797's
![](https://i.servimg.com/u/f95/15/46/86/41/3_robo10.jpg)
"ULTIMITE COX 010: it has a clutch, E starter, throttle, exhaust, aluminum tank, aluminum venturi, gearbox with forward and reverse, and now its on a custom drawn and printed stand"
![](https://i.servimg.com/u/f95/15/46/86/41/sponso12.png)
PAST WINNERS
robot797's
![](https://i.servimg.com/u/f95/15/46/86/41/3_robo10.jpg)
"ULTIMITE COX 010: it has a clutch, E starter, throttle, exhaust, aluminum tank, aluminum venturi, gearbox with forward and reverse, and now its on a custom drawn and printed stand"
![](https://i.servimg.com/u/f95/15/46/86/41/sponso12.png)
PAST WINNERS
Fox 049 standard
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Fox 049 standard
Hey! I recently got a Fox 049. Bought some gaskets and stuff from Matt at EX-Model Engines to make it look operational. Except...it has a large dimple on the top dead center of the piston! Can anyone advise if this is “normal” or is the con-rod about to push thru the top of the piston?? I kinda think its normal because of the Fox add I found showing a raised bump on the piston:
![Fox 049 standard 43d8d210](https://i.servimg.com/u/f89/19/10/39/29/43d8d210.jpg)
Mone:
![Fox 049 standard 47b35210](https://i.servimg.com/u/f89/19/10/39/29/47b35210.jpg)
![Fox 049 standard 43d8d210](https://i.servimg.com/u/f89/19/10/39/29/43d8d210.jpg)
Mone:
![Fox 049 standard 47b35210](https://i.servimg.com/u/f89/19/10/39/29/47b35210.jpg)
Marleysky- Top Poster
Posts : 3618
Join date : 2014-09-28
Age : 71
Location : Grand Rapids, MI
Re: Fox 049 standard
I don’t know if that is normal or not. I have two Fox .049’s and one .07 and none of them have a raised bump. In your picture it does look like it was machined that way. If it is indeed a poor fitting con rod then it will have an audible click when turning over and if disassembled it will be obvious if it’s pushing through.
Cribbs74- Moderator
Posts : 11904
Join date : 2011-10-24
Age : 50
Location : Tuttle, OK
Re: Fox 049 standard
The identifier for the .049 piston is the raised bump. The .07 is a flat top. The piston isn't poking through. The piston is cast and it will shatter like a piece of glass if you try and reset it. The identifier for the cylinder is the base thickness at the bottom, the .049 has a thick base and the .07 has a very thin base due to it's longer stroke. The other is the amount of cooling fins, the .049 has 9 fins whereas the .07 has 7. I could also be reversing those numbers as I always forget but one has more fins.
Ken Cook- Top Poster
- Posts : 5542
Join date : 2012-03-27
Location : pennsylvania
Re: Fox 049 standard
I believe the "bump" is actually some sort of rivet. It is a sure way to distiguish the .049 from the .07.
Oldenginerod- Top Poster
- Posts : 3985
Join date : 2012-06-15
Age : 61
Location : Drouin, Victoria
Re: Fox 049 standard
THANKS GUYS! It seem that the OEM (FOX) used a rivet to assemble the piston and Con-rod Socket together, so the dimple is OK. I do remember reading your post Ken, on how you shattered a piston in a attempt to re-set the ball socket, so I'm definitely NOT gonna do that!![lol!](https://2img.net/i/fa/i/smiles/lol.gif)
![lol!](https://2img.net/i/fa/i/smiles/lol.gif)
Marleysky- Top Poster
Posts : 3618
Join date : 2014-09-28
Age : 71
Location : Grand Rapids, MI
Re: Fox 049 standard
Oldenginerod wrote:I believe the "bump" is actually some sort of rivet. It is a sure way to distiguish the .049 from the .07.
Correct as the piston and socket were made separately. I'll try to dig out some of the socket parts. There were a small handful when we bought all the parts from Doug Martin.
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