Mechanical fuel pump

[3son]

I acquired a low mileage GM goodwrench 5.7L out of a '90 Chevy 1/2 ton. I'm converting it from TBI to carb. I finished drilling the hole for the fuel pump pushrod to run a mechanical pump. I noticed a smaller hole approx 5/16 or so located above the oil pan mounting surface. Is this a oil return hole needing to be finished drilled or leave it alone? Hopefully someone has done this before and can give me some guidance. Search function is down at the moment so couldn't do any homework. Thanks , James

73 Chevy c20
350 sbc

[Captkaos]

Are you saying the 90 model engine came without a mechanical provision and you drilled the hole for the fuel pump.  What about the cavity for the pump to mount?  And what about the camshaft that doesn't have the pump eccentric on it?

[3son]

The engine block has provisions for mounting a mechanical pump, but the pushrod hole between the pump and cam was not machined to final dimensions. I simply enlarged it so the pump pushrod could be inserted. That is when I noticed the smaller hole. The motor received a small summit cam (sum-k1102) this weekend so I could have the fuel pump eccentric.

[Captkaos]

Where is this hole located?  Can you post a pic?

[3son]

Here's a pic showing the smaller hole. I think it's an oil drain back hole, but not sure. Unfortunately I don't have any other SBC motors available to investigate this personally.

Thanks,

James

[VileZambonie]

Wouldn't it have been easier and cheaper to run an electric fuel pump? Hopefully you drilled it at the proper angle and dimensions and didn't get any metal inside the engine.