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Fuel and brake piope to exhaust minimum distance
mgb281 - 16/1/25 at 02:16 PM

I have started to plumb the brake and fuel lines into my MGB GT. Due to the extent of the modifications it will not pass the 8 point threshold for a classic cars it will have to have an IVA test. Now that it will have a twin pipe exhaust the fuel and brake pipes travel parallel to the exhaust and about 7cms away. I have looked in the IVA manual and there is nothing regarding distances or heat protection, when it had the four cylinder engine the exhaust ran one side of the tunnel and the fuel, brake and electrics ran the other. I can run the electrics inside the car but it's the brake and fuel lines that are the problem.
It wouldn't be a problem in running a dimpled aluminium heat shield to keep the heat away but would it pass the test. I have tried calling the local test centre but that is only for booking theory tests.

jacko - 16/1/25 at 03:08 PM

How did the MGB v8 do it ?
It may give you ideas
G

mgb281 - 16/1/25 at 03:18 PM

They ran a single pipe system like the 4 cylinder cars, since I have centralised the fuel tank I don’t have room for a large silencer on the near side anymore, just room for a smaller one each side. I am hoping that I won’t have to make a new system, it will be tricky.

jacko - 16/1/25 at 06:32 PM

Can the brake and fuel pipes run though the inside of the shell like rally cars?.
What are the fuel pipes make off

mgb281 - 16/1/25 at 06:47 PM

All the pipes are cupronickel. The reason that I am asking the question is because I don’t know what can be done. I have assumed fuel pipes hidden under the carpet would be a real no no. Brake pipe is a possibility but what about mot inspection.

Theshed - 19/1/25 at 12:07 PM

7cm sounds like a fair gap to me. I would doubt that the brake pipes would get warm enough to boil the brake fluid. The same is probably true of the fuel pipe and I doubt whether the IVA man would like that running through the car. There are loads of products available for heat shielding pipes and cables that just slip over the pipe. Probably easier than a separate heat shield.

mgb281 - 20/1/25 at 06:47 PM

I went to the Exeter IVA test centre today and got the answer, 7cms is too close without a heat shield. 5cms is okay with a heat shield made with that dimpled aluminium sheet you find on all modern cars, ideally about 2.5cms from exhaust and an equal amount from the brake/fuel pipes. If the pipes are wrapped with insulation it will fail because they cannot inspect the pipes. Hopefully this will help someone else.

Slimy38 - 21/1/25 at 09:00 AM

quote:
Originally posted by mgb281
If the pipes are wrapped with insulation it will fail because they cannot inspect the pipes.


Oddly enough that was the first thing I thought about. I remember rubber coated lines are similarly frowned upon, so directly wrapping them with insulation would have the same outcome.

I'd be interested to know how you apply the heat shield, are you just going to have a wall of shield or perhaps a rigid V shape between exhaust and pipes? Or are you thinking about something a bit more profiled to one or the other?

mgb281 - 21/1/25 at 09:58 AM

I went to the Exeter IVA test centre today and got the answer, 7cms is too close without a heat shield. 5cms is okay with a heat shield made with that dimpled aluminium sheet you find on all modern cars, ideally about 2.5cms from exhaust and an equal amount from the brake/fuel pipes. If the pipes are wrapped with insulation it will fail because they cannot inspect the pipes. Hopefully this will help someone else.

mgb281 - 21/1/25 at 10:15 AM

If you look at the attached photo you can see the two chassis rails underneath the MGB, they are attached to and terminate at a crossmember about halfway along the floor pan, after the crossmember I have actually added a pair of rails that are welded to the crossmember and run back to and are welded to the leaf spring mounts. The two exhaust pipes run parallel to each other and pass underneath those depressions in the crossmember, that gains over a cm of ground clearance which is needed in these cars

[img]http://[/img] Description
Description

You can see the fuel pipes that I have temporarily fitted and the crossmember that they pass through, the idea is to make a L shaped heat shield that runs underneath the exhaust pipe and vertically downwards about 2.5cms from both exhaust and fuel/brake pipes. by spacing the heat shield off the floor then the interior should also remain cooler

[Edited on 21/1/25 by mgb281]

mgb281 - 21/1/25 at 10:22 AM

[Edited on 21/1/25 by mgb281]

SteveWalker - 22/1/25 at 11:38 AM

quote:
Originally posted by mgb281
I went to the Exeter IVA test centre today and got the answer, 7cms is too close without a heat shield. 5cms is okay with a heat shield made with that dimpled aluminium sheet you find on all modern cars, ideally about 2.5cms from exhaust and an equal amount from the brake/fuel pipes. If the pipes are wrapped with insulation it will fail because they cannot inspect the pipes. Hopefully this will help someone else.


Yet some production vehicles have brake pipes running through body cavities or along enclosed tunnels and so the pipes can never be inspected at MOT.

mgb281 - 22/1/25 at 07:55 PM

My wife has that on her car, the MOT states that the pipes are not available to inspect. I suspect that the manufacturer has had the “out of sight” installation approved, possibly by using kunifer pipe in a protected environment they get approval. As amateur builders we wouldn’t get it passed