GM documentation for LT-1 single fuel line

[Mike E.]

The JG indicates that an LT-1 has a single fuel line (no return) as opposed the the dual line on Rochester-equipped cars. I don't even begin to question the accuracy of that. What I do wonder is where is that documented in GM documentation? I don't think I have overlooked that in my AIMs--have I? Is it documented somewhere else? And if not in the AIM, how did the factory get it right? Just curious.

[James G.]

Re: GM documentation for LT-1 single fuel line

Good question... I just went through the 71 AIM and cannot find the single line specifically called out for the LT1.

[Terry M.]

Re: GM documentation for LT-1 single fuel line

I ssUme y'all looked in the LT1 option section.

Since I am at a Regional I have no access to my AIMs.

Y'all might also consider we have looked at hundreds of 1970-72 LT1s. That is better than any AIM.

Also some of us have been looking at LT1s since 1970. Early 1970 at that.

When you buy the Judging Guide you are getting not only our knowledge gleaned from Chevrolet documentation; you also get the experience of the authors and that is priceless.

[James G.]

Re: GM documentation for LT-1 single fuel line

I checked every page after not finding it in the Fuel system section or the LT1 section.
It does call out the LT1 specific fuel pump, however nothing about the single supply line.

[Patrick H.]

Re: GM documentation for LT-1 single fuel line

I checked every page after not finding it in the Fuel system section or the LT1 section.
It does call out the LT1 specific fuel pump, however nothing about the single supply line.

Same here.

You have to remember, though, that our AIM copies are not perfect.
No notation in the LS6 section either, but we know it's true.

[Joe L.]

Re: GM documentation for LT-1 single fuel line

The JG indicates that an LT-1 has a single fuel line (no return) as opposed the the dual line on Rochester-equipped cars. I don't even begin to question the accuracy of that. What I do wonder is where is that documented in GM documentation? I don't think I have overlooked that in my AIMs--have I? Is it documented somewhere else? And if not in the AIM, how did the factory get it right? Just curious.

Mike------


The 1970-72 LT-1 used fuel pump GM #6470110 aka AC type 40709 (type 40956 for 1972). These fuel pumps had no provisions for a fuel return line. In addition, no external fuel filter with provisions for fuel return was used for LT-1 application. Lastly, LT-1 equipped 1970-72 Corvettes used fuel tank GM #3967746 (without EEC) and GM #3967755 (with EEC). These fuel tanks had no provisions for fuel return. So, with a fuel pump and fuel tank with no provisions for fuel return, I think we can safely and accurately infer that no fuel return line was installed.

[Joe L.]

Re: GM documentation for LT-1 single fuel line

Same here.

You have to remember, though, that our AIM copies are not perfect.
No notation in the LS6 section either, but we know it's true.

Patrick------


There's a strange thing about LS-6: the only fuel pump I've ever been able to determine that was used for LS-6 is the AC type 40770. This fuel pump has provisions for fuel return. However, the fuel tank used for LS-6 was a tank without provisions for fuel return. So, I don't know how this worked.

[Tom R.]

Re: GM documentation for LT-1 single fuel line

Mike------


The 1970-72 LT-1 used fuel pump GM #6470110 aka AC type 40709 (type 40956 for 1972). These fuel pumps had no provisions for a fuel return line. In addition, no external fuel filter with provisions for fuel return was used for LT-1 application. Lastly, LT-1 equipped 1970-72 Corvettes used fuel tank GM #3967746 (without EEC) and GM #3967755 (with EEC). These fuel tanks had no provisions for fuel return. So, with a fuel pump and fuel tank with no provisions for fuel return, I think we can safely and accurately infer that no fuel return line was installed.

The makings of a great footnote for the 7th edition!

[Leonard M.]

Re: GM documentation for LT-1 single fuel line

I know from past use my 1970 AIM has missing sheets. My

1970 AIM's LT1 section ends at sheet A6.

My 1972 AIM LT1 section shows the single fuel line on sheet A8 "fuel line clips".

[Mike E.]

Re: GM documentation for LT-1 single fuel line

Patrick------


There's a strange thing about LS-6: the only fuel pump I've ever been able to determine that was used for LS-6 is the AC type 40770. This fuel pump has provisions for fuel return. However, the fuel tank used for LS-6 was a tank without provisions for fuel return. So, I don't know how this worked.

LS6 definitely came from the factory with the dual line.
Joe, how did you determine that the LS-6 came with a tank without provisions for fuel return?

[Mike E.]

Re: GM documentation for LT-1 single fuel line

I ssUme y'all looked in the LT1 option section.

Since I am at a Regional I have no access to my AIMs.

Y'all might also consider we have looked at hundreds of 1970-72 LT1s. That is better than any AIM.

Also some of us have been looking at LT1s since 1970. Early 1970 at that.

When you buy the Judging Guide you are getting not only our knowledge gleaned from Chevrolet documentation; you also get the experience of the authors and that is priceless.

[James G.]

Re: GM documentation for LT-1 single fuel line

Mike,
When I was going through the AIM yesterday...
The callout for the LS6 - (fuel pump and fuel line wise) is that the AIM states - "assembles the same as LS5".
WHEREAS
The LT1 fuel pump is specifically called out in the 71 AIM under the LT1 section and illustrated, however there is not an illustration of the single feed line to Pump "S" rubber hose.

[Joe L.]

Re: GM documentation for LT-1 single fuel line

LS6 definitely came from the factory with the dual line.
Joe, how did you determine that the LS-6 came with a tank without provisions for fuel return?

Mike------


Of course, there's no fuel tank information for the LS-6 in the AIM. GM SERVICE parts information is somewhat "vague" on what fuel tank was used. The best I can make out, the tank was the GM #3967755. This tank has no provisions for fuel return. However, if the LS-6 actually did have a fuel return line, then the tank used must have been the GM #3967749.

One curious note: with a fuel return line, the LS-6 would be the only Holley carburetor-equipped Corvette that ever had a fuel return line. Just so no one gets the wrong idea, we're talking about an actual fuel return line and not an EEC return line. All Corvettes with a fuel return line have the line mounting to the top right side of the tank. EEC return lines are always found on Corvettes with EEC and that line always connects to the top left side of the fuel tank.

[James G.]

Re: GM documentation for LT-1 single fuel line

I racked my memory trying to come up with another example, however I couldn't come up with any other GM car which had a 4 bbl holley and a return line.