Replacing the fuel pump in a small-block Chevy engine
There are two holes in the passenger side front of the engine. The top bolt hole will align with the fuel pump push rod and will have a 3/8" x 3/4" bolt in it.
This bolt needs to be removed and a longer 3/8" bolt installed in its place. Some block assemblies are supplied from the factory with a 3/8" by 7/8" bolt with (2) thick washers under the head allowing the OEM bolt to be re-inserted without the washers to secure the rod in place. Once the (2) fuel pump mounting bolts are tightened, the bolt securing the push rod can be removed and re-inserted with the washers under the head thereby preventing contact with the rod but sealing the hole.
The longer bolt is to gently hold the fuel pump push rod in the retracted position- pushed in towards to center of the engine.
The camshaft has a lobe on it that causes the fuel pump push rod to move in and out- it is what makes the pump, "pump". Total travel of the pump rod is about 0.394' (10 mm). This lobe needs to be positioned in such a way that the rod is furthest back, away from the pump. While this isn't absolutely necessary (I'd try it first with out rotating the engine), it can make installing the pump a little easier.
So, with the longer bolt in the upper hole, carefully tighten the bolt until it contacts and holds the push rod from sliding back out against the spacer plate, remember just finger tigth or you'll bend and or nick the push rod.
Remove the fuel lines, plug them to prevent dirt from entering.
Remove the fuel pump mounting bolts, then the pump.
Clean all the way around the fuel pump hole in the spacer.
If for some reason the hole in the front of the block can not be accessed, an alternative to this is to remove the spacer plate, remove the push rod and put some heavy grease on the cam end of the push rod. This grease will (for a while) hold the push rod to the cam in the retracted position. Reinstall the spacer plate, use a new gasket or RTV to seal it. If (more like when) the push rod slides away from the cam, you can re-stick it a few times before the grease quits working.
With the gasket previously stuck to the fuel pump (use RTV or rubber cement) and the ports and fittings plugged so no dirt can enter, insert the fuel pump arm into the hole in the spacer plate. It helps to start the arm into the hole turned slightly clockwise from straight up, then rotate the pump and arm counter clockwise as you insert it. This will let the arm get in front of the push rod and will start the pump arm to compress if the cam on the camshaft is causing the push rod to be out more than if it was on the lowest part of the cam.
Once the pump arm is in position, you'll have to push against the pump's return spring pressure to get the pump's mounting holes close enough to the spacer to start the bolts. If you are unable to do this, you may need to rotate the engine a bit to let the fuel pump cam retract the push rod. BEFORE you do this, you will need to loosen the bolt holding the push rod in position so the push rod can move.
Once the fuel pump mounting bolts are started, tighten them evenly (one side then the other) until the pump meets the spacer.
DO NOT forget to remove the longer bolt holding the push rod. Replace the original bolt into the same hole, with a little sealer on the threads.
Reattach the fuel lines- do not use teflon tape.