Fuel pump leak

[77 K20]

So 14 months ago when I installed my GM 383 I foolishly followed the advice of the owners manual and bought the mechanical fuel pump they recommended for it. GM part # 12355612 This stupid pump had clearance issues with the motor mount and barely fit down there. AND it cost $100.
It is now leaking. It isn't the fittings. I removed the one, re-sealed it, and put it back on. The whole area there is a MESS. Having never owned one of these multiple piece ones is this common for them to leak? Maybe a seal blew out? Or do you have to remove them and re-tighten them every year?
I'm not able to actually see where it is leaking. I had it idle in the driveway for 35 minutes after I cleaned the whole area. Not a drop out of it. Go for a drive, pull over 5 minutes later and the WHOLE fuel pump is wet in fuel. The lower radiator has fuel on it. The next 2 spark plug wires back are wet. There is fuel all over the motor mount. There is fuel on the engine cross member. The fuel had dripped off of the cross member and onto the front differential. BUT when I am then staring at it, it isn't leaking.
So only seems to happen with probably 50% throttle or higher.

And instead of just fuel, it seems to be oily and doesn't really evaporate. But smells like gas...

Should I even bother messing around with this? Last thing I #@$ need is to have my truck burn up. I've already lost 2 cars due to idiot kids crashing into them. This truck is my daily driver now. Any recommendations of a good performance fuel pump that won't take a big ol' dump in a year?

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[rich weyand]

Why wouldn't you just use the stock fuel pump? If I'm reading the parts book right, GM #6471180 is listed for 1977 K-20 w/350, 400 w/4BC, w/AT. It's like 27 bucks at rockauto.com. You're not going to pull more fuel than a 400, right?

BTW, pix on the net show this as having the return line outlet. If your truck no longer has the return line, you want to use the pump that doesn't have the return outlet.

The problem with "performance" parts is that they are often not as vetted as the GM mass production parts.

 

[77 K20]

I was using that pump because that was the one GM recommended for my crate motor. I'm sure it is way bigger than it needs to be, but I followed their instructions.

So I spent 6-7 hours last night reading on fuel pumps. I was looking at the install instructions for some Edelbrock one that is quite similar to the GM one I have. There was a note in there:

For off-road and race track applications we suggest the use of a
shield between fuel pump and wheels to proven dirt from plugging
pump vent hole.

Vent hole? What vent hole? So I went out and looked at mine- it was coated in clay from a recent trip out where I fell into some ruts where someone else got stuck and the front differential bottomed out and sent a big wave of clay and water directly up into the engine bay. So I spent quite a bit of time cleaning and de-greasing the whole area. The leak is a mixture of gas and oil, as there was oil hanging from the bottom of the fuel pump 12 hours after driving.
I ran a small nail thru the vent holes to make sure they were not plugged. I tightened up the 10 screws holding the assembly together, the 2 bolts that hold the pump on to the bracket, and the 2 bolts that hold the bracket to the block. I went on a 6 mile drive at 70 mph (over 3,000 RPM for me) with a WOT blast to pull back onto the highway. Doesn't look like the pump is leaking, but I might need to drive it for longer to tell for sure.

Sounds like maybe without a functional vent hole on it I could have over pressurized it and caused a leak on the seals on it? Maybe tightening the screws down re-sealed it now.

I don't know- I have my doubts it is fixed but I learned a little bit about them anyway. Now I'm going to be checking it every time I drive it.

Oh- I also read sometimes a seal can fail and it ends up pumping gas past the pump rod into the engine itself (dumping gas into the oil). I checked my oil and it smelled like oil and not gas. Apparently a few have ruined engines from too much gas in the oil and it destroyed bearings.

 

[77 K20]

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In this picture you can see one of the vent holes. It is the little one back kinda where it will bolt to the engine. Being that it is down lower you can see now dirt gets piled up in that area and will plug it for sure.

 

[77 K20]

Now that it has sat for a few hours went out and checked it again. Still leaking oil. Looks like oil is just seeping out of it and drops of it are hanging out on the underside of it.