Mechanical fuel pump ?

[adkphoto]

I got a brand spankin' new Edelbrock mechanical fuel pump to compliment my new engine.

My question is .... the stock setup has a return line to go back to the tank, but the new pump only has inlet and outlet (to carb) ports.

Can i just block off the return line to the tank or is there a goos reason why I shouldn't?


David

[bpmcgee]

I believe that the return line is what keeps the pump from providing too high a pressure to the carb.

Since the pump is driven by the crank, the faster the engine turns the higher the pressure. Most carbs don't like more than about 7 PSI.

Can you get an edelbrok pump with the correct plumbing? That would be the best solution, IMHO.

Brian

[1971LT1SWBPOSI373]

I ran into this very problem a few years back and if I remember correctly this also ties in with the charcoal canister and fuel tank vent system. I plugged the system and went to a vented cap, but the tank still didn't vent very well. I'm not sure what the correct solution is and I looked all over for a schematic of the fuel system, I never did find one. Good question!

[mdill]

Be carefull when replacing the lines to the
canister, GM put restictors in some of them,
so when replacing a vent line be sure to check
and see if there is a restrictor in the old line.
If so cut it out and put it in your new line.

Mike D.

[GREEN70-72]

If I am not mistaken(an I may be) don't mech. fuel pumps have a set range from the factory. and they have a port(hole,whatever)for atmospheric(sp?) reference?

[Longhorn Man]

Read the instructions on your carb, if memory serves, that pump is more like 15 PSI. You'll need to run a fuel pressure regulater and if it has a return line on the regulater, then just hook it to your existing return line.
If you have a choise of a reg with, and one without a return line, get the one with a return line. It helps to keep your fuel cooler and puts less wear on your pump.

[adkphoto]

Actually the fuel pump is supposed to match the Performer series carbs and put out 6 psi.

Here's a link from Summit: http://store.summitracing.com/partde...=MG&part=12478

I was always under the assumption that the fuel pump pressure is constant and the volume changes with RPMs. Somebody correct me if I'm wrong.

Just to play devil's aadvocate... If a bypass back to the tank is needed, why do they make mechanical fuel pumps with only inlet and outlet ports?


David

[Longhorn Man]

If a bypass back to the tank is needed, why do they make mechanical fuel pumps with only inlet and outlet ports

Becouse some carbs wan 6 PSI, and some aftermarket race only carbs may want 12 psi. This way, you can use the pump that pumps 15PSI and 'govern' it down to 6 and have a good return flow going to help with vapor lock. The high line pressure also would help with vapor lock.