67 fb (with 69 pont 400) and a mechanical fuel pump. the return fuel-line is long gone, it now has a mechanical fuel pump with a return outlet. if i dont block it off(return outlet), fuel runs out the bottom.(motor running or not).
Question is...is there any harm in placing a T into the fuel inlet line and having the return line attach back to the T ? i figure its the same as where the fuel will end-up anyway...just cutting out the return to the tank.

OR do i just drive it with the returned blocked off?
and does this cause and overload in the fuel pressure to the carb or pump?

just getting this her back on the road and tring not to do anymore road-side repairs as possible. thanks

I think you just plug it. It's just an extra outlet.

i thought that too, but some people were having problems plugging it, and getting fuel pressure too high.

if you could find a pump w/o return, you could use it. Mr. Gasket makes one for offroad use, or maybe look one up for an earlier pontiac.

i dont know what the effect would be of putting pressure to the return side with a T. I wouldn't try it... maybe with a 1way valve i might.

I used a Carter mechanical for many years with no problems. It had no return, just in and out. I plugged the return hose that went back to the tank. Never measured the fuel pressure, but, like I said, no problems.

If the sending unit has a return line and the fuel pump does not have a return port, there is no harm in blocking the return line. If both the sending unit and the fuel pump have a return line, use it. If the fuel pump has a return line and the sending unit does not, the right way to do it is to install a different fuel pump or a different sending unit and line unless the fuel pump specifically says the return port can be blocked off.

My Holley pump came with an extra outlet port that was pluged but came with fittings to allow hooking up the return. I was curious and fiddled with it and determined the two outlet ports were connected internally anyway. The fitting for the return line was a nipple with a small orifice to limit the return flow.

If the fuel pump has a return outlet you need to run a return line or get a different fuel pump. I tried the "plug the return outlet on the pump" route and the car immediately started flooding and fouling plugs. I raplaced the missing section of return line and connected the pump and it cured the problem.

Many aftermarket pumps have provisions for returns, but are not necessary. Stock replacement pumps are not made the same way....apparently.

I am a new guy. Have just started trying to make the 67 400 he(son) bought safe to drive. Well I have been working fuel pump dumping fuel for the last couple of days. Took the pump off, repaired the supply line, found the return line deadend on right side of engine compartment. Went to the autoparts store for new pump. Well there happened to a "expert" on early GM big blocks in the place. He said the early carburetors would flood out with "normal pump pressure" so GM put on a pump that supplied a lower pressure with high volume and returned the unused fuel to the tank. So what that means is if you are a purist and want to use the original carb. you will have to have the return line. You can not use a "stock GM" pump and plug the line as pressure will go to high at low power setting. In my case I intend to hook up the return line, reinstall the pump and drive on.

Welcome Bill!