CORKYVET

Removed cannister today on '74. Line is plugged to gas tank. Can I just drill small hole in cap. If so, all the way through or just bottom part? Thanks in advance.

CORKYVET

Any comments welcomed. Got the drill ready.

PatsLs1vette

i drilled top and bottom on mine worked fine.

ROD NOCK

I purchased a NAPA replacement cap (in black plastic) and popped the (check valve) vent out. $7 later.

standup

I've heard that this can be done, but I don't know how big to drill the hole... you can buy vented gas caps though......beware, I read a post on here a few months back about a vented cap that failed and caused the tank to implode.....

Why have you removed the cannister????

Just curious because I'm having real trouble with mine--the valve on the tank has gone west and it's siphoning gas through the cannister.......since I can't find a new valve (and I also have to replace the steel line because it's corroded).....I might have to use a vented cap and plug the line at the tank...though I'm not too keen on a possible leak over my exhaust..........

ROD NOCK

First off, I didn't drill my cap with a 'thru-hole'. I didn't want my cap vent hole pointed straight up in case fuel purged out, and shot on the gas door, paint and could run down to the exhaust.
The so called 'vented' cap I purchased only allowed pressure to escape, not allowing air to return and equalize the tank. So I removed the check valve assy (easy access) on the bottom of the cap.
And if fuel happens to purge under pressure, it's routed down around the underside of the cap, (by cap design) and will take the same route as an overfill spill. This seemed like the best solution to me. :chevy

stingry

Before you drill that cap check ou the replacement price.

You may be better off buying a new cap and selling that Vented Cap to someone.

PS If it is not an original cap then DRILL away!

hunt4cleanair

Quote:

Removed cannister today on '74. Line is plugged to gas tank. Can I just drill small hole in cap.

This suggestion may be a bit foreign but why not "de-plug" the line and make it work like it was intended? The system is designed to be a closed system with the vacuum sucking the gas vapor back into the combustion cycle. I don't recall if 74 has the liner (may have been 75) but the vented gas cap compromises the effectiveness of the system designed to be sealed.

Nothing more obnoxious at a meet with shiney, polished Corvettes than the smell of gasoline...that could have been averted by the owner doing the proper repairs rather than the bubba approach! Don't mean to offend but it is easily fixable with the problem probably in the cannister.

OkeeGuy

when i rebuilt my engine i did it as in the "old days"...
no smog junk...just an old fashioned, hot rod type small block with headers etc...i removed my can too...
i remember whenever i removed my cap to gas up it would purge a huge sucking sound...
sometimes if i hadnt removed the cap to gas up in a while it seemed to be starving for fuel under acceleration as well...
i drilled a 1/16" hole thru the top layer only of the cap...
i could then suck AND blow (with my mouth) thru the top of the cap...
its been great ever since...
no ,more "starving" and no more "pressure" sound when removing the cap to gas up...

markdtn

The 63-69 vented cap is still available from GM (at least 3 mo ago). It was only $20. Nice and shiney. Direct interchange for the 70-74.

Fevre

That is what I have heard also, just one small hole in the top is all that is needed, need to do this myself.

OkeeGuy

actually, thinking back, i dont even think it was 1/16"...
it was like the smallest bit i had in the box...
i used to get a big, long wooshing sound...that cant be good!
now...no more sound or pressure!

CORKYVET

SIGNGUY - I'm looking at my cap and I can not see where drilling through the top layer will relieve anything. Appear's it is all sealed from the tank. Anyway to explain?

CORKYVET

SIGNGUY?