LT-1 gas tank configuration

[Mike E.]

I know the LT-1 cars have only the single line along the frame (fuel line) with no vapor return line.
Does the LT-1 tank have any outlets/nipples toward the top of the tank along the outboard ends? If so, how many?
Thanks

[Jeremy D.]

Re: LT-1 gas tank configuration

Mine had a fuel separator valve attached to the tank on the drivers side. There's no fuel return line, but there's a VAPOR return line, at least on '71's. One line went from the tank to the valve, then a line from the cartridge to a line on the frame that goes to the vapor canister, methinks.

[Edward J.]

Re: LT-1 gas tank configuration

Mike, if your car is a 70 LT1 car it has no EEC canister emmisons, and no fuel return, then the gas tank would have only the fuel line that exit the sender. later 71/72 had EEC emissons which has only the additional nipples for the vapor line return and the return hence a closed none vented gas cap.

I dont think they left any additional lines that may be blocked, if thats what your looking for.

[Roger O.]

Re: LT-1 gas tank configuration

Mike, if your car is a 70 LT1 car it has no EEC canister emmisons, and no fuel return, then the gas tank would have only the fuel line that exit the sender. later 71/72 had EEC emissons which has only the additional nipples for the vapor line return and the return hence a closed none vented gas cap.

I dont think they left any additional lines that may be blocked, if thats what your looking for.

Ed,what cap should the 70 LT1 use , vented or unvented ?

[Edward J.]

Re: LT-1 gas tank configuration

Roger, vented cap,unless you have calif. emmison ua9

[Terry M.]

Re: LT-1 gas tank configuration

Roger, vented cap,unless you have calif. emmison ua9

Ed I agree with your answer to Rev. Mike's question --

but my original 1970 gas cap has the word SEALED embossed into it. I doubt that means it is vented. In fact the vent for the 1970 (and I think 1971 and 1972, but I will defer to others on that) is soldered into the top of the tank.

Oh NO NA9 on my 1970 either. The same fuel cap was used for ALL of 1970 model year Corvette production. You might want to refer to the 1970-72 TIM&JG for a drawing of the gas caps for those three years.

[Roger O.]

Re: LT-1 gas tank configuration

Roger, vented cap,unless you have calif. emmison ua9

This vented nonvented 69-70 cap thing has always been a gray area to me.

[Roger O.]

Re: LT-1 gas tank configuration

Ed I agree with your answer to Rev. Mike's question --

but my original 1970 gas cap has the word SEALED embossed into it. I doubt that means it is vented. In fact the vent for the 1970 (and I think 1971 and 1972, but I will defer to others on that) is soldered into the top of the tank.

Oh NO NA9 on my 1970 either. The same fuel cap was used for ALL of 1970 model year Corvette production. You might want to refer to the 1970-72 TIM&JG for a drawing of the gas caps for those three years.

Terry , does your original cap have a gasket on it ?

[Jeremy D.]

Re: LT-1 gas tank configuration

The vent was indeed soldered on my '71 tank. As far as I know and have been taught, ALL LT-1's and ZR's of that vintage have sealed gas caps.

[Terry M.]

Re: LT-1 gas tank configuration

Yes there is a gasket on it, and there is only a spring under the top of the cap. No valve of any kind. The spring keeps pressure on the gasket and also provides the feel of a "notch" as the cap is installed and removed.

I think the word SEALED means just that.

[Roger O.]

Re: LT-1 gas tank configuration

Yes there is a gasket on it, and there is only a spring under the top of the cap. No valve of any kind. The spring keeps pressure on the gasket and also provides the feel of a "notch" as the cap is installed and removed.

I think the word SEALED means just that.

Sorry i wasn't arguing that you have a sealed cap. Some have said the sealed cap on cars without EEC came without a gasket. Others have said it was the locking gas cap that was used without a gasket on nonvented tanks.I'm just trying to figure out this whole cap thing. Most people and books say 70 and newer took the sealed cap and 69 and older took the vented cap. But the 69 shp and 70 shp had the same gas tank. The 3967746 tank had the vent in the tank and it works well for relieving pressure but I wouldn't trust it for venting. I've seen too many tanks sucked down and caved in from the valve failing.

[Joe L.]

Re: LT-1 gas tank configuration

Sorry i wasn't arguing that you have a sealed cap. Some have said the sealed cap on cars without EEC came without a gasket. Others have said it was the locking gas cap that was used without a gasket on nonvented tanks.I'm just trying to figure out this whole cap thing. Most people and books say 70 and newer took the sealed cap and 69 and older took the vented cap. But the 69 shp and 70 shp had the same gas tank. The 3967746 tank had the vent in the tank and it works well for relieving pressure but I wouldn't trust it for venting. I've seen too many tanks sucked down and caved in from the valve failing.

Roger------


All 1963 -69 Corvettes used a VENTED gas cap. From about July, 1969, Corvettes began to be equipped with fuel tanks that had the integral pressure/vacuum valve. Nevertheless, 1969 Corvettes were equipped with the vented gas cap right until the end of 1969 production. So, effectively, these cars had two pressure/vacuum valves-----one integral with the tank and the other as part of the fuel cap.

All 1970-74 Corvettes used a SEALED gas cap and had an integral pressure/vacuum valve in the tank just like late 1969. It did not matter which emissions system 1970 Corvettes were equipped with (i.e. 49 state or California) as far as the gas cap was concerned---all were sealed.

As far as 1/4" nipples on the tank, no 1970-72 LT-1 tank had a nipple on the upper, right (passenger) side. 1970 LT-1 with 49 state emissions had no nipple on the upper left (driver) side. 1970 LT-1 with California emissions and all 1971-72 had a nipple on the upper left side.

[Edward J.]

Re: LT-1 gas tank configuration

Terry , you are correct, I thought the non canister equipted cars had a vented cap . sorry Roger the TJG does have a non vented cap(Sealed)

[Roger O.]

Re: LT-1 gas tank configuration

Thanks Joe that clears it up for me. I like the idea of the double venting and other than judging it couldn't hurt.

[Joe L.]

Re: LT-1 gas tank configuration

..... other than judging it couldn't hurt.

Roger-------

Actually, it might. I believe the reason that GM changed from the vented cap to the integral, tank-mounted pressure/vacuum valve was to help reduce gasoline fume "intrusion" into the passenger compartment, especially a problem with C3 convertibles. Some folks think that the change was due to emissions regulations but I'm virtually certain it had little, if anything, to do with that. After all, with EITHER the vented cap or integral pressure vacuum valve the tank vents to the atmosphere. There's no difference in that regard and, as far as I've been able to tell, there's no difference in the "calibration" of the vented cap versus the integral pressure/vacuum valve. I think the reason that some folks think the change was for emissions reasons is because there were other emissions-related changes taking place about the same time. But, I think the emissions issues and the tank venting issues were, basically, unrelated. So, all that was changed was the LOCATION of the venting, not the venting, itself.

In the early 70's GM discontinued the 63-69 tanks without integral pressure vacuum valve and replaced them with tanks with the integral pressure vacuum valve. They also recommended that any 63-69 which had its tank replaced with a SERVICE tank (with integral valve) use the SEALED type cap.