Fuel Tank Vent

We are switching from a under the seat tank to a front tank on a blown sbc dragster. We had a Jaz roll over vent(#8 an)on the old tank and installed it on the new. After welding up the tank, we filled it with water to check for leaks. When we went to empty it out the 1.250" outlet it acted like it was restricted. Opened the fill cap and the flow picked up. So the million dollar question, is the vent big enough? The roll over vent was for a safety concern when it was near the driver but isn't as big of one now. Of course we didn't put a access hole in the tank to get the valve out and don't want to drill a new hole and fill it up with drilling crap. We don't think we had a problem with it last year as it never sucked the tank in but don't know if it restricted fuel flow. Using a 1100 pump with a best last year of 4.04 @174 with .96's 60 fts. Lots of fuel at the hit to kill the tire shake then pull a bunch out with timers.

 

I just installed a 1.25" inlet in my tank (from 1") and I have a #10 vent, did the fill with water and let drain, whoosh no problem. If you are opening the cap and flow is going up ,then you need larger vent.

 

Need a one inch vent and forget the rollover valve now that is in the front. stick it up and put a shark fin on it to somewhat pressurize the tank at speed.