1970 LT1 Gas Cap..Vented or Not ?
02-05-2003, 05:46 AM
#1
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1970 LT1 Gas Cap..Vented or Not ?
I don't have the orignal cap and wondered if any one knows (I'm sure I'll get the answer becasue this board is great) if it should be a vented or non-vented cap
Thanks in advance
Thanks in advance
02-05-2003, 05:51 AM
#2
Le Mans Master
Re: 1970 LT1 Gas Cap..Vented or Not ? (soapy)
I think you need non vented.. I said I THINK....I may be wrong but I believe the switch came in very late 69 ...
P.S ... Ijust looked at a very reliable web site.. The doctor says '70 used non vented (sealed). I have a late 69 with a sealed cap.
[Modified by silvervetteman, 5:59 AM 2/5/2003]
P.S ... Ijust looked at a very reliable web site.. The doctor says '70 used non vented (sealed). I have a late 69 with a sealed cap.
[Modified by silvervetteman, 5:59 AM 2/5/2003]
02-05-2003, 09:54 AM
#3
Melting Slicks
Re: 1970 LT1 Gas Cap..Vented or Not ?
I don't have the orignal cap and wondered if any one knows (I'm sure I'll get the answer becasue this board is great) if it should be a vented or non-vented cap
The information provided by silvervetteman is correct. The change from a vented to a sealed cap was scheduled for late 1969 when fuel tanks with a pressure relief valve were put into production, but it is not clear if the cap change was actually carried into production during the 1969 model year. By 1970, however, all Corvettes were equipped with a sealed cap and this is what your LT-1 should have.
The 1970 style cap was zinc plated and had the word "SEALED" stamped circumferentially into the face of the cap. Late in 1970, a red tag was added with the words "CAUTION OPEN SLOWLY" in white letters... This cap/tag combination was carried through to the end of 1971 production. Beginning with the 1972 model year, the tag was eliminated and the "CAUTION OPEN SLOWLY" warning was stamped into the cap along with "SEALED".
From a strictly functional standpoint, any of the caps listed above will work in your application. Generally the only time problems occur is when a sealed cap is used with a non-vented (mid-1969 and earlier) fuel tank.
Currently, the 1968-1969 "VENTED" and the 1972-1974(?) "SEALED - CAUTION OPEN SLOWLY" are the only caps available... Both are still serviced by GM. I seem to recall the "VENTED" cap priced around $20 when I purchased several last year, but you'll have to verify that... I would guess that the other cap carries a similar price.
The "SEALED" cap that was originally installed on your car is no longer serviced by GM, is not reproduced, and is very expensive in the used parts market when you can find one... Figure on $150-$200 for something presentable. Paragon reproduces the tag for the very late 1970-1971 caps, but it differs quite a bit from the original.
Good luck in your search!
Regards,
02-06-2003, 05:23 AM
#5
Le Mans Master
Re: 1970 LT1 Gas Cap..Vented or Not ? (Rowdy Rat)
I don't have the orignal cap and wondered if any one knows (I'm sure I'll get the answer becasue this board is great) if it should be a vented or non-vented cap
Soapy,
The information provided by silvervetteman is correct. The change from a vented to a sealed cap was scheduled for late 1969 when fuel tanks with a pressure relief valve were put into production, but it is not clear if the cap change was actually carried into production during the 1969 model year. By 1970, however, all Corvettes were equipped with a sealed cap and this is what your LT-1 should have.
The 1970 style cap was zinc plated and had the word "SEALED" stamped circumferentially into the face of the cap. Late in 1970, a red tag was added with the words "CAUTION OPEN SLOWLY" in white letters... This cap/tag combination was carried through to the end of 1971 production. Beginning with the 1972 model year, the tag was eliminated and the "CAUTION OPEN SLOWLY" warning was stamped into the cap along with "SEALED".
From a strictly functional standpoint, any of the caps listed above will work in your application. Generally the only time problems occur is when a sealed cap is used with a non-vented (mid-1969 and earlier) fuel tank.
Currently, the 1968-1969 "VENTED" and the 1972-1974(?) "SEALED - CAUTION OPEN SLOWLY" are the only caps available... Both are still serviced by GM. I seem to recall the "VENTED" cap priced around $20 when I purchased several last year, but you'll have to verify that... I would guess that the other cap carries a similar price.
The "SEALED" cap that was originally installed on your car is no longer serviced by GM, is not reproduced, and is very expensive in the used parts market when you can find one... Figure on $150-$200 for something presentable. Paragon reproduces the tag for the very late 1970-1971 caps, but it differs quite a bit from the original.
Good luck in your search!
Regards,
Soapy,
The information provided by silvervetteman is correct. The change from a vented to a sealed cap was scheduled for late 1969 when fuel tanks with a pressure relief valve were put into production, but it is not clear if the cap change was actually carried into production during the 1969 model year. By 1970, however, all Corvettes were equipped with a sealed cap and this is what your LT-1 should have.
The 1970 style cap was zinc plated and had the word "SEALED" stamped circumferentially into the face of the cap. Late in 1970, a red tag was added with the words "CAUTION OPEN SLOWLY" in white letters... This cap/tag combination was carried through to the end of 1971 production. Beginning with the 1972 model year, the tag was eliminated and the "CAUTION OPEN SLOWLY" warning was stamped into the cap along with "SEALED".
From a strictly functional standpoint, any of the caps listed above will work in your application. Generally the only time problems occur is when a sealed cap is used with a non-vented (mid-1969 and earlier) fuel tank.
Currently, the 1968-1969 "VENTED" and the 1972-1974(?) "SEALED - CAUTION OPEN SLOWLY" are the only caps available... Both are still serviced by GM. I seem to recall the "VENTED" cap priced around $20 when I purchased several last year, but you'll have to verify that... I would guess that the other cap carries a similar price.
The "SEALED" cap that was originally installed on your car is no longer serviced by GM, is not reproduced, and is very expensive in the used parts market when you can find one... Figure on $150-$200 for something presentable. Paragon reproduces the tag for the very late 1970-1971 caps, but it differs quite a bit from the original.
Good luck in your search!
Regards,
All youever wanted to know about gas caps but were afraid to ask.
02-06-2003, 05:40 PM
#6
Safety Car
Re: 1970 LT1 Gas Cap..Vented or Not ? (Rowdy Rat)
As an add on to what the Rowdy one reported..."first-design pressure caps (before 1972) would blow off at 1-2 psi pressure." In 72, they beefed up the tank straps, tank and the cap to withstand a greater internal pressure (from fuel evaporation). So what rat man said works for 72 or later because it can accommodate earlier less than adquate caps. It also suggests that while GM restoration parts have been tuned to accept either configuration...early caps may be less than adequate on a 72 car sitting in the desert!
It takes a minimum of 1/2 psi to make the canister system work (trap vapors and ready for carb). At this point, the gas cap contains vapors and forces them to the canister.
It takes a minimum of 1/2 psi to make the canister system work (trap vapors and ready for carb). At this point, the gas cap contains vapors and forces them to the canister.
