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When changing the fuel pump there is a small bolt that is replaced by a larger bolt to hold the piston during replacement. My question is what is the purpose of the bolt directly beneath this small bolt? Currently there is no bolt on my engine. Don’t remember if I took the bolt out while removing the fuel pump, water pump, a/c brackets etc. Should have taking photos.
I don't know what engine or accessories your '72 has, but my '71 350, 4 spd, non-A/C, non-pwr brakes car doesn't have anything in that lower hole. My guess is that the lower hole probably is there due to engine manufacturing commonality to be used for mounting something on another car model
On my engine I just put a short bolt into it to fill the hole. But otherwise it's an empty hole. Perhaps a accessory bracket mount hole for another model car?
Yes, there is a hole there. Yes, you can jam the fuel pump pushrod in place with a longer bolt.
No, you shouldn't, because screwing this up could be catastrophic. Hold the pushrod in place with some grease instead, and make sure the fuel pump cam lobe is in the all-the-way retreated position.
Find the #1 plug wire on your distributor cap and make note of the position of the #1 tower.
Pop the distributor cap off and then "bump" the engine over (using the starter) until the rotor points to the #1 tower position.
Put the cap back on
Remove the old fuel pump
Remove the plug bolt from the front of the engine block for the fuel pump pushrod hole location. All small block Chevys have this bolt:
Using your fingers, needle nosed pliers, or a screwdriver, push the fuel pump pushrod upwards until it hits the camshaft eccentric. It should move upwards about an inch from its current "dropped-down" position. Hold it there.
Install a fully-threaded 2" long bolt into the hole that you pulled the plug bolt out of. Tighten the bolt until you feel it hitting and jamming the pushrod.
Install your new fuel pump and snug it down.
Remove the 2" long jam bolt and re-install the stock plug bolt.
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