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MG Midget and Sprite Technical - NMC hard fuel line connections

My other classic is a 1984 Porsche 924 which I'm currently restoring.

I need to replace some of the hard fuel lines which have been bodged in the past. The feed to the engine is 10mm, and the return is 8mm. The bodged lines have Flares (DIN/Bubble) at one end connected to hard lines under the car, and compression at the other end which connects to flexible fuel hose to the pump and tank.

Getting suitable copper pipe and compression fittings isnt a problem. However forming the correct DIN flare needs an expensive tool for 8 and 10 mm pipe. I could probably ask my friendly garage to form the flares for a small fee.

Which is the best method for joining the two pipes, compression or fares ? I have been warned that flared ends can give trouble? Can I safely use compression fittings?

The fuel system runs at a working pressure of 70 PSI.
Chris Madge

I'd be tempted to find out what Porsche did originally and copy that. At 70psi you want to be totally confident with your chosen fuel line connections.



Jeremy MkIII

Chris,

When I needed some special copper brake lines making up I used a large motor spares shop in Bristol, a very knowledgeable lady made them up whilst I waited. They had the professional flaring tools so made a great job first time - might be worth checking if they do fuel lines as well.

I cant remember off the cuff the name of the firm (may not exist anymore) but if its of interest I'll dig it out from the filing pile !

If you want to join copper pipe you can use brass cup/cone fittings (solder the pipes to the fittings - silver solder best) - these fittings are used on steam engines and can handle 70psi easily.
Would have to checkout available sizes, I have used them for engines and on a boats diesel system but can't remember sizes.

R.
richard b

Chris

I would find a good independent Porsche 924 parts specialist. The 750MC runs a race series for them so other folk about who want these things too.

Pipe suppliers to try - ask Automec first
Think Automotive. https://www.thinkauto.com/
Glencoe Ltd (used to FSE Fuel System Enterprises) https://www.glencoeltd.co.uk/
Automec (custom brake and fuel pipes, kits and fittings) https://automec.co.uk/collections/fuel-feed-kits
https://automec.co.uk/collections/clutch-fuel-reservoir-pipes

Motorsport component suplliers
Merlin Motorsport https://www.merlinmotorsport.co.uk/
Raceparts https://race.parts/
Trident Racing Supplies https://tridentracing.co.uk/

Thanks
Mike
M Wood

I used to race a 924; there should be some help in this list:
http://www.924gt.com/servicing.html

then there's also
https://www.design911.co.uk/
https://www.porscheshop.co.uk/
https://www.pro-9.co.uk/

finally the downloadable parts catalogue here:
http://www.924gt.com/docs/924petcatalogue.pdf

HTH
David Smith

Thanks for the replies. Ready made pipes from Porsche are available and they will happily take £100 off you for each pipe. Pretty much every thing is in multiples of £100 or bigger when it comes to Porsche parts. So i was looking for a cheaper solution.

I have sourced the 8 and 10mm pipe off ebay and decided to go with flares where they join the rubber pipes, and compression fittings where they join other hard lines.

I asked around several garages but 8 and 10 mm isnt a common size for cars. Eventually I found a truck mechanic who put some flares on for me FOC.

Next I need to work out the routing and how to bend the pipes without kinking them.....




Chris Madge

Chris,
Screwfix do small bore hand pipe benders for copper - micro bore etc 6-10mm .
I have a small one I use on brake lines and steam pipes works OK.
Mine is old and I think a Record make.
richard b

If one end isn't flared, you can also use a bending spring. Available in 8 & 10mm.

https://plumbingsuppliesdirect.co.uk/10mm-pipe-bending-spring-for-external-use-with-10mm-copper-pipe/
Dave O'Neill 2

If for any reason you no longer have the original pipes or they've been cut, or you've forgot how the pipes run, you could use some thick wire to first check the routing and bends required, also checks for easiest installation method (what other bits do or don't need removing).

Whatever you see anywhere don't bend any copper pipe over your knees, it can bugger your knees up and often your knee can be the wrong size anyway.

Obviously that 8mm pipe will have to be cut and re-ended as there's already a crease in it, you and the MoT testers will know that's there if you leave it. 😜
Nigel Atkins

I'll live with the crease, its from the edge of the die where the chap made the flare. Its tiny and isnt going to be safety or MOT issue. However if i blow up in a ball of flames you can say I told you so ;)

Some of my wife's coat hangers have been repurposed to make a template of the routing. Hopefully I'll be able to bend them back into coat hanger shapes un-noticed.

China's finest pipe bender has been ordered.
Chris Madge

I'll live with the crease, its from the edge of the die where the chap made the flare. Its tiny and isnt going to be safety issue. However if i blow up in a ball of flames you can say I told you so ;)

China's finest pipe bender has been ordered.
Chris Madge

I was thinking of cosmetics with the piping defect, that and your conscious knowing that it is there detracting from Porsche standards - but perhaps it'll polish out. 😊

Wire coat hangers, BL repair kit, are far and few between now don't waste them, you must have some neighbours with wire fencing, or local private school.

If you've any spare straight tubing a bit of practice with the bender is useful for doing double or offset bends particularly on different axises(?) planes(?) (and to avoid creases).

If you get a set wrong, or to make them easier to do, you can cut on the straight between them and inset a straight coupler.

If you're going to joint two pipes that you are going to bend remember to allow for any wastage of pipe length(s) from making the bends.
Nigel Atkins

The pipe bender finally arrived which allowed me to fabricate the two fuel lines from the tank/pump over the gear box, behind the torsion beam that goes across the back of the car and connects to the pipes under the car that go to the engine.

Bending 10 mm pipe around some tight and complicated bends was a challenge. I got there in the end although trying to get the 8 and 10 mm pipes running parallel and equally spaced was almost impossible. However it looks a lot better than it was and is now properly secured with OEM clips rather than zip ties.

Getting good photos was tricky with the car just on axle stands.





Chris Madge

Maybe not original but looks neat enough to me! Always difficult getting tidy bends that close to the flare nuts. Well done!
GuyW

Nice job Chris, I'd be pleased if I'd done it that well :-)
David Smith

This thread was discussed between 24/02/2021 and 13/03/2021

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