Converting vented to non vented gas cap
Is there an easy and safe way to convert a vented gas cap to non vented for my 62? Can't seem to find a non vented anywhere. Not going to judge so brand etc. not an issue.
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Re: Converting vented to non vented gas cap
Jack:
The gas tank must have a vent somewhere to function properly. If your car's gas tank has another small vent somewhere, great........otherwise you need the vented cap.
Not certain what is provided on a 1962 car.........but on my 1967, the ONLY vent for the gas tank is through the vented gas cap.
Larry
Checkout this link for a non-vented cap: http://www.topflightrepro.com/corvet...on-parts.shtml A bit pricey, but that's your call.Last edited by Larry M.; August 24, 2011, 10:53 AM. -
Re: Converting vented to non vented gas cap
just drill a 1/8" hole in the cap. we did that on the 3X2 carb engines to keep them from filling the crankcase with gasoline. the heat from the mufflers heat up the tank and cause it to pressurize and you could hear it when you opened the tank. air could get in thru the cap but pressure could not get out till we dilled the holeComment
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Re: Converting vented to non vented gas cap
During mid-57 production, the gas tanks were vented and continued afterwards with a vent. On 57-62 tanks, there is a very small steel elbow on the passenger side, top of the tank. There is a small hose (or supposed to be, may be severely deteriorated by now) connected to this elbow and it runs across the top of the tank (retained in place by small clips along the tank). The hose comes through a rubber grommet at the upper right corner of the fuel filler box. Open the fuel door and you should see this hose------------that's the vent. Thus, the gas caps up through mid-57 were vented, After that, the caps were non-vented.Comment
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Re: Converting vented to non vented gas cap
The tank is vented. I guess with a vented cap I just have double venting. Trying to get away from having to crank and crank to start the car after it has been sitting for awhile. Figured the gas was draining back into the tank. Guess it could be evaporating and a non vented cap would make no difference.Comment
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Re: Converting vented to non vented gas cap
if you have a corvette with a Q jet carb and the fuel pump has a return to the tank line you need to use a in the carb fuel filter with a check valve to prevent the gasoline from draining out the fuel line. i know you 62 does not have a Qjet but this post is just general info.Comment
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Re: Converting vented to non vented gas cap
Jack------
The caps that GM has cataloged to SERVICE your application for many years have been, from what I can tell, of the vented type. So, apparently, GM approves the use of the vented cap for your application.
The currently available GM cap for your application is GM #14002439. About 20 bucks, GM list.In Appreciation of John HinckleyComment
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Re: Converting vented to non vented gas cap
Thanks, I'll see if I can find one.Comment
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Re: Converting vented to non vented gas cap
Joe -
I think the (vented) cap shown in P&A for '57-'62 is a long-running error. We know for a fact that only four caps were ever released and used in production, and all of them were of solid riveted construction, with no valves or vents of any sort (the drawings are in Noland's book):
#3742472 was used from mid-'57 through mid-'58
#3751022 was used from mid-58 through 1962
#3751027 was used from '61 through '62
#3764641 was used from mid-'58 through 1962
Another cap, #3787292, was released for Service use only on a TSB in November, 1960, which was identical to the #3764641 except it used a 2-way pressure/vacuum valve to prevent leakage and provide venting; this cap was never used in production. Why it was stocked for the TSB (which dealt with fuel leakage) is something of a mystery, as the tank didn't need a vented cap - it was already vented, starting in mid-'57.
The use of a solid non-vented cap (as used in production) has been well-known for many years as the only cure for '57-'62 fuel leakage at the cap; many vendors sell a vented cap for '57-'62 usage (maybe due to the vented cap in the P&A), and all of them leak fuel.Comment
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Re: Converting vented to non vented gas cap
The cap that was on the car when I purchased it in 1991 didn't even fit and leaked at the filler. Got another and it leaked. Latest one from O'Reilly at least doesn't leak but is vented. It may be that the gas is just evaporating between starts and a non vented wouldn't cure the problem since the tank is vented anyway. Guess I won't know unless I try one. Just hate cranking and cranking and I'm sure not going to prime the carb. Like my skin too much.
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Re: Converting vented to non vented gas cap
Jack,
Installing a non-vented cap will have no effect on a truly ''dry' carb' during starting attempts. Look elsewhere.Comment
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Re: Converting vented to non vented gas cap
The long cranking is due to evaporation from the carburetor, not the tank. The tank just adds to the stink in your garage. My 63 had a cap with just a plain small hole in it. In an attempt to limit the evaporation from the tank, I got the replacement cap which has the two way valve (vacuum and pressure), but it didn't make much difference. There is not too much you can do to solve this problem as the Ethanol laced gas is the main culprit. You might realize some improvement by finding a source for non-ethanol gas or avgas, but that will only get you "back to the day", i.e. it will just take a little longer to evaporate like back in the 70's or 60's.
Stu FoxComment
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