Help need fuel line size
Thread Starter
Instructor
Joined: Jun 2006
Posts: 153
Likes: 0
From: va beach VA
Help need fuel line size
I have a 86 corvette and need to know what size the stock supply and return lines are under the car and how much hp they will suport the car is getting a ls1 with a 97 vette return type fuel system. thanks
Le Mans Master
Joined: Jan 2002
Posts: 9,036
Likes: 13
From: Edmonton AB
Originally Posted by CFI-EFI
The supply is 3/8" and the return is 5/16".
I've never studied the C4 S/R lines, but when I read up years ago
in preparation for adding a return line from a regulator for a carbed
car, the collective wisdom was to size the return to be equal to or
larger than the supply.
As I recall, the premise is that if the return line cannot be guaranteed
to pass more fuel than the supply under all conditions, then the
fuel pressure to the carb can rise above the value set with the regulator.
Perhaps this is more important with float-controlled carbs?
.
Race Director
Joined: Sep 2000
Posts: 17,298
Likes: 33
From: The Top of Utah
Originally Posted by Slalom4me
Interesting.
I've never studied the C4 S/R lines, but when I read up years ago
in preparation for adding a return line from a regulator for a carbed
car, the collective wisdom was to size the return to be equal to or
larger than the supply.
I've never studied the C4 S/R lines, but when I read up years ago
in preparation for adding a return line from a regulator for a carbed
car, the collective wisdom was to size the return to be equal to or
larger than the supply.
Originally Posted by Slalom4me
As I recall, the premise is that if the return line cannot be guaranteed
to pass more fuel than the supply under all conditions, then the
fuel pressure to the carb can rise above the value set with the regulator.
Perhaps this is more important with float-controlled carbs?.
to pass more fuel than the supply under all conditions, then the
fuel pressure to the carb can rise above the value set with the regulator.
Perhaps this is more important with float-controlled carbs?.
RACE ON!!!
Le Mans Master
Joined: Jan 2002
Posts: 9,036
Likes: 13
From: Edmonton AB
Apologies if it seemed like I was disputing CFI-EFI's post. This
was not the meaning I intended, it is more of an 'oh' response.
The 'guaranteed to ...' bit is just expressing that if the return
line can't handle the volume by-passed by the regulator, then
more pressure is seen by the carb - as has been acknowledged.
While fuel usually isn't introduced to the circuit mid-stream, expansion
from heat can increase its volume. Also, fittings, bends and other
restrictions in the return line can impede flow. Maybe the thinking is
that if one is working with only a few lbs pressure and trying to control
the variance closely, then it matters more. Too long ago to remember.
.
was not the meaning I intended, it is more of an 'oh' response.
The 'guaranteed to ...' bit is just expressing that if the return
line can't handle the volume by-passed by the regulator, then
more pressure is seen by the carb - as has been acknowledged.
While fuel usually isn't introduced to the circuit mid-stream, expansion
from heat can increase its volume. Also, fittings, bends and other
restrictions in the return line can impede flow. Maybe the thinking is
that if one is working with only a few lbs pressure and trying to control
the variance closely, then it matters more. Too long ago to remember.
.
Race Director
Joined: Sep 2000
Posts: 17,298
Likes: 33
From: The Top of Utah
A small, even a 1/2 pound, difference in pressure is a greater percentage of the 6 to 8 psi a carbed system uses, than of the approx 40 psi common with EFI. Therefore, The carbed system would be more sensitive to small changes in pressure than EFI. The "guaranteed
to pass more fuel" phrase, already accounts for the "fittings, bends and other restrictions in the return line". In any case, it makes no sense to me why the return line that will have less volume to handle, has to have a greater capacity than the supply line.
RACE ON!!!
to pass more fuel" phrase, already accounts for the "fittings, bends and other restrictions in the return line". In any case, it makes no sense to me why the return line that will have less volume to handle, has to have a greater capacity than the supply line.
RACE ON!!!
Instructor
Joined: Oct 2000
Posts: 152
Likes: 0
From: des plaines, il
It's not exactly GM engineering, but see the line size discussion here:
http://www.gnttype.org/techarea/fuel...nearticle.html
http://www.gnttype.org/techarea/fuel...nearticle.html
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