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Petrol breather question

19 Sep 2016, 6:35pm
Just about finished sorting the petrol filler pipe out but unsure about the anti glug breather.
I have cut the breather pipe at the filler, blocked the end that goes into the filler pipe and extended the anti glug breather. I was going to fit a 6mm rivnut to the highest metal part of the petrol filler to give a fixing point for the breather tube but feel it might a weak point. I was wondering about fitting a one way air valve to the end of the pipe instead. That way air can be forced out when filling the tank but hopefully won't let out the smell of petrol fumes after the tank has been filled.
Any idea if this will work or will it just let fumes out on a hot day as the tank warms up?
19 Sep 2016, 7:40pm
Jaguartvr wrote:
Just about finished sorting the petrol filler pipe out but unsure about the anti glug breather.
I have cut the breather pipe at the filler, blocked the end that goes into the filler pipe and extended the anti glug breather. I was going to fit a 6mm rivnut to the highest metal part of the petrol filler to give a fixing point for the breather tube but feel it might a weak point. I was wondering about fitting a one way air valve to the end of the pipe instead. That way air can be forced out when filling the tank but hopefully won't let out the smell of petrol fumes after the tank has been filled.
Any idea if this will work or will it just let fumes out on a hot day as the tank warms up?


Not a good idea
The air needs to travel both ways or a vacuum will be created in tank
I have seen modern plastic tanks crushed when a vent got blocked
20 Sep 2016, 8:10am
Thanks for the reply and that makes perfect sense, back to plan A
21 Sep 2016, 9:24pm
Re: Fuel pipe
Exactly what I have done ! But you need to use a 2" to 1.5" 90 degree bend at the filler cap and a 2" to 1.5" 90 degree bend at the original filler. (Car builder solutions page 393) connect with 1.5" flexi silicone fuel pipe (Car builder solutions page 395). This will give clearance for the tyre in wheel arch.
The flexi pipe you are using is not the best for fuel use.
It is better to keep the original (so called anti glug breather pipe). In place and
Connect another one above the original and connect (as you have done) to the top of the new filler.
The tank does not breath through this pipe when the sealed cap is on, but breathes through a charcoal filled filter at the front of the car.
Access to the tank pipe can be reached by cutting a 2" hole, with a hole cutter in the wheel arch, then weld or bond back after modification.
Hope this helps , it works for me!
22 Sep 2016, 7:21am
I think it needs pointing out that if you start chopping into the chassis you are running the risk or danger of IVA. Especially now you have said this in print they could argue the chassis has been modified.
22 Sep 2016, 7:31am
It was one of the reasons that I didn't remove the metal flaps that I cut and folded them over themselves, nothing has been removed. I call it an adjustment rather than a chop!
You could say the same on the MX5 as you have to cut away part of the front headlight frame.





With the filler pipe, 2" seems to give me plenty of clearance and it all sits above the inner plastic wheel arch splash panel. I am still waiting for the sikaflex tank N so it could change! When I clue the 90 degree pipe into the existing fuel pipe it will block the existing breather hole which was why I extended it
up to the top elbow.
I used CBS budget fuel pipe because A: I'm a cheapskate and B: the ends of the pipe are smooth sockets to accept the ends, the more expensive flexible pipe is cut to the length you want so both ends have the metal spiral. I thought having the metal spiral under the jubilee clip might leave a tiny gap.
Do have any info on your bonnet vent chrome grill. It looks great and is just what I want to do, a couple of close up pictures would be greatly appreciated.