Can't get carb port caps to last

[Asa]

Hey guys.
There are a couple vacuum ports on the Carter YF I have on my 200. The ones I have are (as far as I can tell) the correct size, but I replaced them maybe 4 months ago and now they've split already. I drove the car to the gas station and back, and that's it.

No clue what happened, maybe I just got bad quality caps?
Anyone have this issue before?

 

[CNC-Dude]

An unfortunate side effect of having alcohol blended gasoline. The alcohol in the gas vapors are breaking down the rubber much faster than non-blended gasoline. Try tapping the holes and put a threaded plug in them.

 

[vntgtrk]

The right size sheet metal screw works just fine. If you use one for, say, vacuum tuning, use a piece of vacuum hose with a machine screw in that. Not pretty, but works and lasts.