Fuel System ??'s for LS1 into '72 C3
Thread Starter
Teching In
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From: Port St. Lucie, FL
Fuel System ??'s for LS1 into '72 C3 Dropping a LS1 with a Magnuson supercharger into a '72 Vette and had some questions about fuel delivery. First question is will I need a return line or will a single line be ok. Also, the stock tank is unbaffled. Will I need to order a baffled tank? What size fuel line shoudl I go with? Any help or advise appreciated! 
TECH Regular
Joined: Feb 2004
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I had a wild c3 myself. Car constantly scared the crap out of me with the unpredictable oversteer.
Anyway to your questions. I had fuel delivery problems on mine when it got warm. I had to pressurize the tank (ie blow in it) to get the fuel pump primed. This was with a carburated car. If you are using the stock tank I strongly recommend you fab in an in-tank pump or get a carter 6psi rotary electric pump to pull the gas from the tank and then to the Walbro or other fuel injection pump.
6AN delivery and return lines are fine. Don't forget the fuel filters BEFORE the fuel pumps.
Baffled tank would be great but not vital.
Regarding return line it depends on what fuel rails you have. For a couple of years the corvette rails had a pressure regulator that was integral with the rails. If you have them then you will have to have a return line.
If not you can elect to have a "deadhead" reglator but I would recommend a return regulator. You can mount it on the rear frame rail under the rear fender (that's where I mounted my fuel filters) and have a short return line to the tank or mount it up front and have a long line.
The LS1 corvettes fuel filters had a regulator and return built in I think.( Do a search of the site to make sure) which is another option for you.
Anyway to your questions. I had fuel delivery problems on mine when it got warm. I had to pressurize the tank (ie blow in it) to get the fuel pump primed. This was with a carburated car. If you are using the stock tank I strongly recommend you fab in an in-tank pump or get a carter 6psi rotary electric pump to pull the gas from the tank and then to the Walbro or other fuel injection pump.
6AN delivery and return lines are fine. Don't forget the fuel filters BEFORE the fuel pumps.
Baffled tank would be great but not vital.
Regarding return line it depends on what fuel rails you have. For a couple of years the corvette rails had a pressure regulator that was integral with the rails. If you have them then you will have to have a return line.
If not you can elect to have a "deadhead" reglator but I would recommend a return regulator. You can mount it on the rear frame rail under the rear fender (that's where I mounted my fuel filters) and have a short return line to the tank or mount it up front and have a long line.
The LS1 corvettes fuel filters had a regulator and return built in I think.( Do a search of the site to make sure) which is another option for you.
You will not have to baffle the tank. I am running a stock tank gravity feeding an inline Walbro 340 pump then the 99+ Corvette fuel filter/ regulator. The return from the regulator goes back to the vent fitting on the top of the tank. I run a single 3/8" aluminum fuel line from the regulator to the fuel rail. I have run the tank pretty low with no starvation issues.
97 & 98 corvettes are the only ones with the two line rails. All other LS1's have a single line feed.
97 & 98 corvettes are the only ones with the two line rails. All other LS1's have a single line feed.
Thread Starter
Teching In
Joined: Feb 2005
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From: Port St. Lucie, FL
Originally Posted by 70 LS1
You will not have to baffle the tank. I am running a stock tank gravity feeding an inline Walbro 340 pump then the 99+ Corvette fuel filter/ regulator. The return from the regulator goes back to the vent fitting on the top of the tank. I run a single 3/8" aluminum fuel line from the regulator to the fuel rail. I have run the tank pretty low with no starvation issues.
97 & 98 corvettes are the only ones with the two line rails. All other LS1's have a single line feed.
97 & 98 corvettes are the only ones with the two line rails. All other LS1's have a single line feed.
Launching!
Joined: Dec 2004
Posts: 274
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From: Kansas City, MO
Running two pumps in series isn't a good idea unless they are matched. A low 6psi pump in the tank feeding a high pressure pump external will cause problems if the first pump can't keep up with the volume. There is a guy with a camaro on this forum with that kind of setup and is burning up the external pump because it is starving for fuel.
Keep it simple, use an intank pump to give you the high psi you need to the Corvette filter/regulator for 58psi and run it to the single fuel rail, where the return on the filter/regulator runs back to the tank.
Now if you go with the dual line fuel rail then the pump to the inlet of the fuel rail then out the fuel rail to a regulator back to the tank return line.
Some people think that the dual lines run to the engine and back to the tank will prevent vapor lock. I think it will help because of the constant flow back to the tank minus what the engine uses but the real solution in either setup is to run the fuel lines away from the exhaust and heat. Vapor lock in carborated engines that use 7psi with lines run near exhaust manifolds has been issues but I think the 58psi alone will help to prevent vapor lock.
Keep it simple, use an intank pump to give you the high psi you need to the Corvette filter/regulator for 58psi and run it to the single fuel rail, where the return on the filter/regulator runs back to the tank.
Now if you go with the dual line fuel rail then the pump to the inlet of the fuel rail then out the fuel rail to a regulator back to the tank return line.
Some people think that the dual lines run to the engine and back to the tank will prevent vapor lock. I think it will help because of the constant flow back to the tank minus what the engine uses but the real solution in either setup is to run the fuel lines away from the exhaust and heat. Vapor lock in carborated engines that use 7psi with lines run near exhaust manifolds has been issues but I think the 58psi alone will help to prevent vapor lock.
Thread Starter
Teching In
Joined: Feb 2005
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From: Port St. Lucie, FL
Originally Posted by jdperk-86elco
Running two pumps in series isn't a good idea unless they are matched. A low 6psi pump in the tank feeding a high pressure pump external will cause problems if the first pump can't keep up with the volume. There is a guy with a camaro on this forum with that kind of setup and is burning up the external pump because it is starving for fuel.
