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Engine basics => Engine set up tips => Topic started by: Timothy Payne on May 05, 2014, 08:42:27 AM
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Hello fellow Americans!
I've picked up a chrome fox 25RC off ebay, believing it to have a 0.738" bore (aka early models).
To cut a long story short, the piston in my 29X is cooked. Maybe the piston on this ebay puchase would be suitable; (however on closer inspection I discovered these later engines to be 0.680" * 0.680".
So as I've completely stripped this beauty, I would be grateful if anyone could tell me the correct threads Fox used for these later units.
..........it ain't UNC is it?
Tim
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Fox engines use standard hardware. Try 4-40, if they're too big try 3-48.
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Fox engines use standard hardware. Try 4-40, if they're too big try 3-48.
Almost certainly 4-40, in fact. Just to be absolutely safe, however, at least try to thread a 5-40 in there. It wasn't that way from the factory, but it is possible that someone had previously stripped it and replaced it.
Brett
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Thanks guys, I'll give that a try!
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I vaguely remembered having trouble finding screws for a 25, (4-40s didn't fit), so I dug one out of the stash. If it's the shiny case, 4-bolt backplate 25 like the one in the pic, they should be 3-48s. The earlier 3-bolt back plate 25 used 4-40s, as did the BB IIRC.
(http://i140.photobucket.com/albums/r26/fbodies/P5050020.jpg)
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I vaguely remembered having trouble finding screws for a 25, (4-40s didn't fit), so I dug one out of the stash. If it's the shiny case, 4-bolt backplate 25 like the one in the pic, they should be 3-48s. The earlier 3-bolt back plate 25 used 4-40s, as did the BB IIRC.
(http://i140.photobucket.com/albums/r26/fbodies/P5050020.jpg)
Definitely they are 3-48. While your at it get the necessary socket head screws from Micro Fasteners or RTL and ditch the really bad Phillips screws that Duke used to save production costs.
dennis
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Thanks Dennis, that's saved me alot of hassle.
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they will definitely look better with the socket screws plus you will be able to uniformly tighten the head and backplate. You should not have any problems with loose screws. Spent an afternoon doing a bunch of Fox engines. Cleaning,replacing gaskets and screws, freeing wrist pins etc. I haven't used any of the old Foxes in years but I insist that they be in perfect running condition. They are now all looking almost as good as t factory fresh.