(Doing the tbi to carb swap) Rather than buy a regulator, I want to use a mechanical pump that I have on hand. Do I just have to take out the sending unit on the electric fuel pump?

 

Yep you need to remove elec pump and replace it with a length of hard line or replace whole sender/pickup with an older non elec pump one.

The mech. pump has a hard time drawing/sucking through the elec pump. Sometimes it will draw some fuel through it (but not enough to support WOT runs) and sometimes it won't even pull any at all through.

Mine would not pull any fuel through, so I cut hole above tank, and removed pickup, elec pump and replaced with length of hardline.

 

My mechanical pump worked for years with a dead in-tank pusher pump. I eventually replaced the in-tank pump with a 255lph whalboro and got rid of the mechanical altogether.

 

just a guess but i would think the early "helper" pumps would be a different story than the later FI pumps that are designed to feed the whole engine needs at 12 or 40 lbs

 

It's quite possible since the old pusher pumps only ran about 3psi and probably weren't that powerful compared to the newer FI pumps.

 

I like the idea of using the pusher pump. Thought is, it keeps the fuel moving from the tank to mech. pump {up front} back to tank. This helps the fuel to not heat and turn in to a vapor in the line. This means the use of the return line has to be used. How ever I get the stock setup may be to restrictive for a Large engine at wide open throttle. I currently am in doing just this.

 

I all so am replacing both fuel lines, tank to pump and pump to tank/return. Routing these line is still in out under consideration of minimal heat transfer to them.


I'll know more in a few months, as I'm just not there yet. Hope this helps in terms of the direction you take.