earlwb

There were two Fox ,74 engine designs over the years. Way back in 1966-67 Fox came out with their new .60 and .74 baffled piston engines. Non Schnuerle ported. The .60 and 74 were discontinued years later but the engine was bored out and sold as a .78 for many years still. The engine had a large strong crankcase that would have let them go up to a .91 or better size engine if they wanted to.

Later Fox came out with the new Eagle Schnuerle ported engines and they resurrected the .74 displacement size at that time.

So yes there can be two different cylinder sleeves out there for .74 size Fox engines. But one needs to be careful as the .60, .74 and 78 cylinder sleeves can look quite alike without closer inspection. same thing for the current .60 and .74 Schnuerle engines too.

Now then with the Schuerle ported Eagle engines. I do not remember seeing any with the rounded top dome shaped exhaust ports. But Fox had patented a design that reduced engine noise by more gradually opening up the exhaust ports.

Also some people had ported their engines to gain some more power too. Also setting up the engines for tuned pipes as well. So it could be something that a individual had done too.

I went and double checked things in my stash of Fox engines and parts. Fox did make a cylinder sleeve with a triangular shaped exhaust port. That was what he patented.

added notes:
Now then I am pretty certain that that cylinder with the raised dome shaped ports and the angled cuts on the intake ports was done by a individual sometime in the past. Whether it worked or not would be the question. From the looks of the cylinder sleeve, it appears to have been run really hot too. The OP might need to check to ensure the cylinder hadn't become warped from the heat.

Hobbsy

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Thanks Earl, I found a "M" cast on the phlange of the cylinder on the left.

Zero

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Group
I have a Fox 45 BB which I acquired recently. It is completely gummed up however I did get it apart to clean it out. One thing I cannot do is get the rod off of the crank so I can remove the piston. Any ideas.

Hobbsy

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You must pull the sleeve out first.

Zero

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I have pulled the sleeve. The rod is loose on the crankshaft pin and also on the piston pin. It moves back and forth on each pin but not enough to lift off of the crankshaft. It looks like I need to remove the wrist pin from the piston but I don't know how to get it out either. Any help is appreciated.
Fred

georgewaldrop

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Charlie,

I have looked, but haven't found any of those articles or the issues of MAN [archived] that contained them.

Hobbsy

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About 15 to 20 degrees to the right of TDC should let it just barely come off with a little pressure from a L shaped Allen wrench.

1QwkSport2.5r

Do the 45 and 50 use the same liner?

Hobbsy

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The Fox .45 has a .850" bore the Fox .50 has a .907" bore, same as the .60.

hsukaria

I would think that the displacement increase comes only from the increase in bore, not stroke. Changing the stroke would impact the crank and crankcase design.

1QwkSport2.5r

I kinda thought the big case Foxes were all .790" stroke. The liner thickness (and bore) was what varied among the B-case engines, I've just never been able to get the .50 piston and rod out of the engine without removing the wristpin. I wondered if the .45 is/was the same way? Hsukaria - did you need to remove the wristpin to get the piston out when you re-ringed your .45?

1QwkSport2.5r

I know the .50 and .60 have the same bore. That's how I got away with using my custom head button in my .50. It worked pretty well - I last got 13,680rpm from a 10x6 APC on 5% fuel after only about 6oz of fuel and using an EZ Adjust carb. I put the MkX back on it now. Waiting for another nice day to run more diesel through it.

Hobbsy

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The .60 and the .74 have a .937 stroke, the .60 could technically be called a long stroke since it's bore and stroke nearly mimic the MOKI and MVVS .61's which are 22.5x24 bore and stroke. The .74 has a 1" bore, it would nice to put a 1" stroker crank in it.

Zero

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I will give that a try tonight.
Thanks for the input.
Fred

Zero

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FormerDairyFarmer

I was able to get the rod off of the crankshaft last night and discovered that the piston ring was broken in half. Thanks for your help
Anyone have an extra one that they would be willing to part with that will fit a Fox45BBRC?
If so please send me a private message.

Thanks
Fred

hsukaria

Hi Zero, you can get a new piston ring from Frank Bowman. I put one on my Fox 45

1QwkSport2.5r

+1 for a Frank Bowman ring. [email protected] is Franks email address.

wnewbury

Fox 45 doing a good job dragging a 4 Star 64 around. Muffler is off a Fox 60 since when I bought the 45 decades ago, it had no muffler. I hope the photo is included.

hsukaria

is the 45 adequate power for the 60-size 64?

wnewbury

Sure. It's a Fox.
How fast do you want to go? At my age, it is just fine. I know some would prefer more power but to me, it is more than adequate.

1QwkSport2.5r

I figured I'd get everybody that has interest buzzing. I took a beat up 1983 Fox .40 single rear ball race engine and put the best piston/liner I had into it and see if it would run on diesel with a Davis head for a K&B .40. The piston has a scratch in it, so it doesn't have great compression to start with so I had my doubts it would run. I had to shim the head for proper head spacing and I found the compression screw didn't offer enough travel of the contra piston to be in the optimum position. With the longer screw, I got a smooth run. The engine will not hand start on diesel, but will on glow fuel. It turned a 10x6 APC at 12,500 on 7% nitro and old style head, and 7,500rpm on a 12x6 MAS k-series on diesel. It would get hot and sag using an 11x6 or 11x7 MAS on glow fuel even set 500rpm rich of peak. It did not get hot and sag on diesel and 12x6 prop.

What I know:
the head fins aren't aligned properly
the compact case engines are said to not be strong enough for diesel use.
A scratched piston doesn't hold compression and seal nearly as well
hardened steel internal c-clips work superbly for wristpin retainers.
Thunder tiger mufflers are significantly quieter than fox mufflers.
It was fun to make this beat up old thing run, but more so on diesel. It ran before, but I didn't expect any reliability from it.

http://youtu.be/i6AvBZ-BcOw

Charley

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1QwkSport2.5r

1QwkSport2.5r

Indeed they are. Much better hold than wire clips but a real pain to get out. Now to see how long the engine holds up....

50+AirYears

Been a while since I last posted on anything. Had to pack up and move South. Finally found a workshop with a couple bedrooms and a kitchen attached. Still unpacking.
After reading over about 30 pages of posts, just thought I'd put in my 2.00 worth (2 cents when my dad got me addicted, current amount adjusted for 67 years inflation!) I've read plenty of comments about how loud their Foxes were. If you think even a .74 or .78 is loud, you've never run an unmuffled short shaft .59! I have one with an old Johnson Automix carb added. That's even louder than my old O. K. Cub .19, which used to leave my ears ringing after just a short FF type run. But for loud, you ain't lived till you've pitted for a Dyna Jet! Like being in the bell of an old lighthouse foghorn.
Maybe now with a new house, I can get back into posting.

1QwkSport2.5r

Good to see you back..