Will polyurethane fuel proof a thank compartment ? Thanks in advance.

Excuse me guys, It's tank. Sorry

Depends on the type. I believe that oil based poly will do a moderate job up to about 15 or 20% nitro. Don't quote me as fact. If you have normal epoxy, you can thin it with denatured alcohol, or put some on the area and hit it with a hair dryer to make it run. Not much is needed for this area, because it will be cold fuel and not hot exhaust residue.
Good luck,
Curtis

I do the thinned epoxy bit and it works very well. Just takes a touch of alcohol, and a little epoxy goes a long way.

Yes, thinned epoxy is the way to go,just not to thin or else it won't dry.

Use the epoxy, but hit it with a heat gun to thin it. That way you don't screw up how much alcohol you put in it.

What Brett65 said, leave out the alcohol, put on as thin a coat of 30 minute or slower epoxy as you can and then hit it with your heat gun. It will thin out and capillary into all the nooks and crannies and give you a good hard fuel proof coating and strengthen up any firewall joints at the same time. I've seen to many gummy messy applications of alcohol thinned epoxy to risk using that technique.

I was going to use lustercoat

Lustercoat is good for fuel proofing but does not add any strength and at $8.00 dollars a can it's kinda expensive.Heating up epoxy makes it thin out? gotta try that sometime,I never had a problem with adding a little alcohol,I guess mabe it depends on the brand of epoxy being used,it does slow the drying time down if ya use to much alcohol.

cowboydfk, yes, heating epoxy thins it out while it is hot. Do not overdue the heat, i.e. don't boil it. As you heat it up you will see it suddenly spread out and flow evenly, do not heat it any further. The heat will also make it set up much faster, that is why you need to use 30 minute or slower epoxy for this kind of application.