i have a mate who is an ally welder, and we’ve spoke about making a pair of tanks for my truck on a few occasions, but we dont know where to buy the filler necks from, could you not use a pair of anti-siphon devices as they are ally and weld them in, or do they need to be detachable incase customs and excise want to dip your tank??
They wont get mine off. 
An easily detachable anti syphon device would surely defeat the object…
Don’t think HMC&E would object if they can’t take a sample it’s their problem not yours,think about diesel cars there’s not many you could take a sample from via the tank filler neck(my Peugeot for a start)
switchlogic:
An easily detachable anti syphon device would surely defeat the object…
yes i agree, i’m sure they only fasten in using discreetly placed allen bolts or something, and as vosa kept my mate for over an hour the other week only to find nothing, i’m sure customs would have no problem making you get your allen keys out if they saw fit - but i’m sure if they were that bothered it would be as easy to simply loosen the fuel filter and see what leaked out?
customs use a fine tube which will get into tank they not after having the tank full away 
R975ENC:
customs use a fine tube which will get into tank they not after having the tank full away
good info - bless them lol - i’ve only been dipped once and that was on test, many years ago. 
If you want a couple anti siphons, i’ve some i’ll sell for £20 each. They’re for 80mm necks and just need a clean as they’ve been sat in my workshop for some time.
What about getting a couple of filler necks cut out of knackered tanks? Phone up a couple of breakers and ask if they have any damaged fuel tanks, cut it out, weld it in, jobsagoodun.
N14ERF:
If you want a couple anti siphons, i’ve some i’ll sell for £20 each. They’re for 80mm necks and just need a clean as they’ve been sat in my workshop for some time.
80mm - is that daf size ?
mucker85:
What about getting a couple of filler necks cut out of knackered tanks? Phone up a couple of breakers and ask if they have any damaged fuel tanks, cut it out, weld it in, jobsagoodun.
do you know any daf/commercial in general breakers? i keep asking scunthorpe daf but they claim not to know any lol 
I think the Germans have an issue with tanks that arn’t origional from the manufacturer.
Think I remember something from years back about Krauts & belly tanks?
sixaxles666:
N14ERF:
If you want a couple anti siphons, i’ve some i’ll sell for £20 each. They’re for 80mm necks and just need a clean as they’ve been sat in my workshop for some time.80mm - is that daf size ?
They are daf size, think it’s quite common though.
Something like these should be available with a bit more searching, not sure if these are large enough, though why you need a 4 inch filler neck on a truck is beyond me anyway !
Why not look at a different design altogether.
Twin tanks with a single filler in the middle pehaps? It would probably be a bugger to syphon without an anti syphon filler.
sixaxles666:
mucker85:
What about getting a couple of filler necks cut out of knackered tanks? Phone up a couple of breakers and ask if they have any damaged fuel tanks, cut it out, weld it in, jobsagoodun.do you know any daf/commercial in general breakers? i keep asking scunthorpe daf but they claim not to know any lol
Just give your local truck breaker a call.
If customs decide to take a sample they will regardless, if diesel thieves decide they want your fuel they will remove the bung from the tank or the fuel pipe or even drill your tank and an anti syphon device will cost you the price of a fuel tank repair and time off the road…
Armstrong:
If customs decide to take a sample they will regardless, if diesel thieves decide they want your fuel they will remove the bung from the tank or the fuel pipe or even drill your tank and an anti syphon device will cost you the price of a fuel tank repair and time off the road…
totally agree about the thieves - which is why i’ve just stuck to a locking cap so far, its a deterrant but not impossible to get past, so in theory should save excessive damage. if they have enough time you simply will not stop them. 
in this instant - for the purpose of making your own diesel tanks, you could use the anti syphon device to make the neck/filler cap and cut off the internals if you were concerned about the bigger picture so to speak.
Amazing, simply putting “weld on filler neck” into google produced 892,000 results in 0.19 seconds.
Some of those results will surely lead to companies who supply such.