bvette1000

I have a 1969 corvette coupe with a mildly built 350. It has a 4sp. transmission and a Holley 750 double pumper, but I am still running the stock mechanical fuel pump. I am planning to upgrade to a 110gph Holley mechanical fuel pump and a regulator. My question is, do I need to use the fuel return line, or can this be blocked off? If I need the return line, what is the best way to do it? The pump and regulator that I bought do not have a port for a return line. Any suggestions? I don't want to screw this up. Thanks in advance.

lars

See my posts and photos in the following topics:

http://forums.corvetteforum.com/c3-t...k-in-a-c3.html
(see my post #20)

http://forums.corvetteforum.com/c3-t...d-by-lars.html

Lars

Stingray Man

You need a return line for sure. Also, isn't a 750 double pumper a bit much for a 350. My last carbureted small block had a 650 double pumper and it screamed!

iNdigo

RobbMC makes a great 1/2" supply/return style fuel sender for the C3.

While true, a 750 DP is probably overkill for your 350, an upgraded fuel system is a great upgrade to prepare for future power. I just installed a regulator with an interchangeable spring to go high pressure if I switch to FI.

I was waiting until I finish my project before posting info, but I did a full AN-8 supply/return setup with pump and regulator, which in the searching I had done, isn't well documented for the C3.

Best,

tbw

bvette1000

I know the 750 DP is a lot of carb, but the fuel system is being designed for future upgrades,(bigger cam, new heads, etc.). Where should I run the return line from? (regulator, back of fuel log, fuel pump?). What about an inline fuel filter with a return port? I realize I am asking a lot of questions, but I would l want to do this correctly. Thanks again for all your help. bvette1000

lars

I answered those questions in my first post to you... all the info is there - all you have to do is read it.

Lars

bvette1000

Thank you Lars, you are right. It is all there if I was paying attention to what I was reading. But now, I have some more questions. (imagine that) What size of line did you reduce down to, and what size is the male an fitting at the outlet of the reducer/resrictor fitting? I would like to do mine just like the one you showed and route it to the factory return line at the frame. Thank you again. bvette1000

Vette5.5

Another thing to consider, is a rear mounted electric pump. I've had good luck with the Mallory 140 set up. Pump and filter at the rear tank and three port bypass regulator for return line on the engine, with dial pressure gauge. I like this on rarely driven cars, as primes the carb for quick start up's, and I switch it off, to stall out on empty carb bowls, when parking.

RatRacer

Another simple solution is to install a fuel filter w/ a built-in vapor return line. I have one installed about 12" before the carb and it prevents vapor lock on my big block, even when it's 100f outside.

MelWff

arent they a little small with 5/16" inlet/outlet?

RatRacer

That's just a generic pic. You can get a 3/8" version at any local parts store for about $3.

RatRacer

Here's a 3/8" version w/ a 1/4" vapor return barb.

http://www.napaonline.com/Catalog/Ca...041_0297054279

http://www.summitracing.com/parts/WI...n/?prefilter=0

iNdigo

Please note that a vapor return is not the same as a return-style fuel regulator.

With a return style regulator, you need two large lines 1/2" or AN-8 ID running from the tank to the regulator. Fuel flows to the regulator, provides its 7psi or whatever you're running, and pushes the excess back to the tank. Recirculation keeps fuel temps down, and the pump doesn't have to work as hard as in a "deadhead" setup, where there is one large supply line and no return, or just a vapor return.

I just completed a project running two AN-8 hoses from tank to regulator in place of the stock hardlines. It can be done with the frame on with a bit of patience and using hose clamps. I'll have pictures up in the next couple weeks.

tbw

STL 71 C3

what makes the C3 need a return line where so many other cars/ trucks do not?

superdave269

Ratracers solution seems simple, but just to clearify - would one run the return line from the filter to the gas tank? I have never seen this set up before and wonder why. It seems like an easy fix. If I was going to do it I would have to cut the metal fuel line infront of my carb but if VL becomes a problem with my car I would do it.

lars

GM used return lines on all their cars and trucks built 1967 and later.

lars

The line for the return fuel coming out the back is 1/4". I would have used 5/16, but -5AN parts are not common. The return line on your frame is 5/16". The restrictor fitting has a .060" diameter hole drilled in it after being welded shut, so flow through the return is not real high - just high enough to keep the fuel circulating to avoid vapor lock.

bvette1000

Thank you Lars, you have been a tremendous help. I have my parts ordered and will be completing this project soon. bvette1000