86 caprice fuel pump
 

Changing a fuel injected to mechanical do i need to just change the sending unit and anything else

Are you changing the TBI to a carb or wanting to change the electric pump to a mechanical? Need more information.

Need a LOT more info Billy....
If you're replacing the factory fuel injection with a carb, leave the fuel pump alone and simply add a fuel regulator. I run a Barry Grant electric fuel pump off the back of my tank. Just before it enters the carb it runs through a regulator that I've set to 6 PSI....
An electric pump will guarantee you're engine will never stave for gas....it also helps eliminate vapor lock as it pushes the fuel better than a mechanical pump....always use braided steel lines too.

i took the v6 ou and im putting a 305 in and it has a mechanical pump i was wondering if i could just chang the sending unit or would it be better to leave the electronic in and just put a regulator like they said

If you install a regulator with a return line, your pump will probably be ok. If it does not have a return line to let extra fuel go back to tank, then your electric pump won't last long.

i was thinking of the same thing before I want to replace my fuel pumps. when I was browsing through the forums I read about this regulator installation thing. Not really sure of what it meant.

The electric fuel injection pumps located in the gas tank of vehicles made since around 1987 are capable of putting out in excess of 60 psi. A carburetor only needs around 6-7 psi to operate properly without pushing gas out of it. A regulator will decrease this high pressure down to what you need. Some are preset and some can be adjusted. Without a way to return excessive pressure back to tank, you will burn the electric pump up very quickly. The pump needs to move fuel to stay cool. This is why your vehicle with an electric intank pump has a return line from engine back to tank. Your engine can't burn that much fuel all the time, so it sends it back.

I've changed four 76-79 Caddilac Sevilles from fuel injection to carb. On those I used the mechanical pump.

If I were doing a swap again, I would want to go with the mechanical pump, as they are, in my opinion, more reliable than electric, easier to change when they fail (that's putting it mildly) and last time I checked the mechanical was still less than $20.

The concern I would have would be that the tanks I did were gravity feed... i.e. the tanks had their outputs on the bottom where they simply drained out. The '92 Caprices I have aren't like that. I "bare boned" several GM beasts (85 Caprice, 89 Custom Cruiser, 87 Electra) and used the mechanical pump with them and a '70 Q-jet and they ran great.

Billy are you sure you want to go to all that trouble and not swap in a 350?
305's are ok, just ok. It's basically a 350 with crappy parts to shorten the stroke so that GM could trick the EPA. There was never any real reason to make 305's.

eventually i want to put a 350 but i have a 305 for now

Well the 305 will be a big improvement over the six. The 305's aren't bad at all, they are great engines and in some ways have a bad rep mainly because the 350 is better, but they're nice engines and aren't sluggish by any means.