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Fv721 fox


Jeff Yost

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1 hour ago, Jeff Yost said:

How do I know correct/stock muffler from repro? 

I am going by the colour, looks like silver or bare metal. Having worked on the Fox over all their service life, around 1975 to 1990, I recall the silencers being heatproof black. You cannot rule anything out. I suggest you contact the previous owner to find what work had been done to the vehicle before the overheating occured. This could provide clues.

Richard

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7 hours ago, Jeff Yost said:

After removing the silencer guard I tapped on the silencer  and it sounds hollow. Could that be a problem?

If there is an obstruction or restriction in the exhaust system it will not allow the hot gasses to pass out quickly enough. A copy silencer may be different inside and any sound absorbing material inside might have moved. As you are not coming up with any faults in the cooling system, we have to widen the field searching for causes of temp rise.

The original silencer was very heavy as I recall.

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1 hour ago, Jeff Yost said:

OK. Was going to drive fox without silencer to see if it would overheat. Best I can tell it is homemade and hollow. Took back cover off and observed ware on the edge of the blower motor belt. Thought of test run with cover off to see if it would not overheat.

 

If I am not mistaken, the photo shows the power steering pump pulley and belt

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He’s not probably right, he is right. There are 4 belts in that area: water pump, power steering pump, alternator & fan drive. You need to have a proper look and make sure they are all there and in good condition. The one in the photo doesn’t look great.

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6 hours ago, Jeff Yost said:

Your probably right. I'm still learning. What do you think about driving with silencer off and back cover off? If it don't over heat then it might help narrow it down?

Thanks for the help

You will find the noise from the open pipe is far to great to go on the road with, although it sounds great (!). When we tested the Fox's after repairs we always left the rear armour off to check for leaks and had a short silencer made to fit the outlet on side of the hull, think it was one from a V8 Rover, you will need something on there. My thoughts are that there is a possiblity tthat sound deadening material in your silencer may be obstructing gas flow, how ever it seems you have not confirmed all the belts are intact yet.

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Fox overheated straight away.  Rads had been serviced and all, seems correct... except the incorrect engine modifications caused excessive heat transfer to eng block.  The sleeves are important in the first series eng, and the high compression car pistons just made it all worse.  I have a later series eng core to rebuild and install... someday?   Newc

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Now that winter is finally over back to work on the fox. Curious if heat exchanger restriction could be possible. Going for a test run soon with out back plate and going to monitor transmission temp. Also am I paranoid about driving at 225 degrees when the manual says do not hard run engine and exceed 240 degrees?

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Well; I haven't run my Fox in 3 yrs, old petrol now. Understand that overheating was always  iffy.  My problem is a bad rebuild on a series one engine.. Series 3 engines had far better cooling passages and even the heads do not interchange.  Newc in Oregon USA

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Drove it maybe ten miles with the back plate off. Seemed to help? Got up to almost 215 degrees at high Rpms. I'm convinced low speeds are fine. Making a vented back engine cover for a 12 mile test run to annual show. Manual says to pull over at 240 degrees. Seems a little hot.

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