1 - I don't know how well you cleaned the tank out after it was welded? I know when I had mine done what came out after the first wash was mingin! so I washed it out LOADS.
2 - you didn't seal it after as Andy recommended, that would help with the fuel going in from then on in.
3 - just increase the breather hole/ improve the breathing! - it can't hurt!!
4 - did you clean out the new lines, made sure there was no swarf/blockage, same with the new hoses?
5 - get your ass to a rwyb and do some testing there, rather than an event you've paid to race at, will only have 3-4 runs a day only to find you still have a problem. rwyb you can really test your modifications and get your car sorted
1 - a LOT but obvously not enough.
2 - I know but I did a fair amount of reading up and some of the cheap "slosh about" sealers get some shoddy reviews. So I put this off till I knew what to get.. Anyone used any thing they recommend? some have scary stories of coming away from the side as if a giant poly bag!
3 - Fair point. But I did run the car with no Cap on to test and there was no change. so I've kinda discounted the breathing issue.
4 - No.. This was brand new hard line and brand new rubber hose. I guess it's hard to tell if brand new hard line might have something in it, but there isn't a flexible hose much longer than 3 inches in the engine bay and only about 6" from the pump.
5 - Good plan. But I think I've nailed it. plus there wasn't really any time for me to get to a RWYB. It's the finals next week so that'll have to be it. :-)
At Shakey last month, it almost became undriveable. So we lifted the tank and the filter was CAKED with crap... So we replaced that, and we took the carb tops off and cleaned everything and we drained the tank and gave it a poor mans clean (sloshed a gallon of fuel about in it and drained it...) and it didn't miss a beat all the way through the next run.
i have since also taken the carbs off the car and taken them apart and given them a proper clean out. something I couldn't do at the track. All the idle jets were blocked.. (Tho one it looked like sand.. We did have some shot blasting done in the Vent area under the rear window, but the filters would stop that.. But the fact the fuel filter was clogged up, My money is on it being INSIDE the tank that's the issue. )
i'm also gonna give the tank a better clean. Rather than the sloshing method I think I'll put the tank on one end with an opening a the bottom. Then put some cleaner in my spray gun and blast it in there to get into all the nooks and drain it through a filter so I can see the crap coming out. When no more crap comes out, I'll assume it's clean...
if I can't get it clean, I have another tank I can use for the finals, but it should sort the issue.
And I have a lead on a genuine early tank.
This kinda explains why it was ok before the works and crap after. there must have still been grinding dust, and weld spatter inside the tank. Not a breathing issue at all.
We will see how this runs now at the finals this weekend.