Bye bye oil cap

[Dcsinclair22]

So maiden voyage today after re wiring, new interior, my youngest son had his prom so I was designated taxi, all went fine until the 2nd run (had to pick up and drop of his girlfriend too) on way back home I heard a horrendous noise, sounded like I had ran over a massive chunk of metal, turns out my oil cap blew off so that's now dead, its a 2.0l pinto, it had a push on metal cap type thing that went over the oil cap itself, they've both gone, any ideas what might cause that to happen? Had a quick search for "pinto oil cap blew of" but seems I might be the only one

[Foz]

The standard pinto oil filler cap is vented with a wire mesh filter built in.   The crankcase should be vented somewhere else as well, either to atmosphere though a catch tank or back into the air intake.  If these are blocked you'll get a build up of pressure in there and something has to give.

I'm guessing it's probably too late to check the filler cap

[Dcsinclair22]

yeah filler cap is gone, I did drive back to see what the hell ot was that had come of/or I had run over when I saw both parts of the cap on the floor squashed I didn't bother retrieving it, it's a busy road so I just thought I'd buy a new one, my catch can is connected somewhere under the carbs, I'm pretty sure it was you who commented on one of my pictures last year about my catch can actually, either yourself or nelmo anyway,

[Jez Morton]

Have you disabled the pcv valve where the breather exits the block? When you run to a catch tank there's nothing to draw the fumes and open the valve. I guessing this is why the pressure built up and popped the cap off.

[Dcsinclair22]

I'll need to double check mate, the car was like this when I bought it, I just replaced the catch can with a different one as the one that was on there originally was leaking out of some of the rivets