Ok I dropped in a blt 1969 350/383. had to mill and tap the block for the starter and do the T-5 conversion.I used the mallory 4309 I think it is with the return,Here is my 2 issues/ Issue 1 = no way the oil pressure swith will fit so I used a spark plug no fault to extend the area for the stwitch to thread in.The older 0010 blocks have a hump right above the oil filter that stops the switch from threading in.What piece do you guys use to extend out or is there a different oil pressure switch I should use ? 2nd prob= the fuel pressure gauge that I put on the fuel log bounces from 5 to about 7 I also installed a set of glow gauges on pods.Its reading about 8psi constant but those gauges read double so if its 4psi it shows 2psi on the gauge.Top end reliable gauges BUT I even tried the mister gasket and the autometer mechanical fuel gauge on the fuel rail and it bounces.The car runs great and did when I drove it down to get its exaust put on today.I need the proper part # or extention piece for the fuel pressure switch as I have a drip a day leak as it wont seal 100% and Im sure will become a drip drip drip and also whats the deal with the gauge bouncing? I did everything under instructions from here so its correct.I just can not correctly set the fuel PSI with the gauge bouncing on the 4309 mallory unit and I can not properly fit the oil pressure switch into place.It was a 305TBI T-5 now its a 1969 350/383 blt with stage 3 conversion clutch and eldebrock headers - 670 street avenger-duel plane eldebrock intake-accel super HEI dist and all, pos crankcase airflow and vacume systems correctly mapped out and connected so I am in use of the PC and I cleared the vats code (did no good BTW still had to use oil pres switch for fuel pump to work so dont waste your time) Any help - thanks in advance.Its a 91 vert

 

1) OPSU

I didn't use one. I simply used the wiring from the OPSU, and used the factory fuel pump relay, to make my fuel pump come on any time the key is ON. My car had the three prong OPSU, I took the two larger wires (fuel pump wires), and ran them to the relay, then ran a ground and a hot-in-run to the relay. So, the relay is grounded, and then with key ON it gets 12v+ from the hot-in-run wire, which activates the relay and switches the power from the one OPSU wire (battery side) to the other OPSU wire (fuel pump side).

For the guage, I simply used the other OPSU (from older model 3rd gen) and installed it on the china wall behind the intake (same place the older cars installed them), and ran my guage wire up to that.

2) Bounce
Mine bounced and changed alot when I first did it - I found my solution several years later - might be your problem too. When I installed my fuel lines and the Mallory 4309, all I had at the time was 3/8 hose barbs. So I "forced" the 5/16 fuel return line over the larger 3/8 hose barb - it was nearly impossible, but I was determined. Turns out, that when I forced the smaller fuel return line over the larger hose barb, the barb edge literally cut the inside of the rubber hose, making a "flap" inside the rubber hose. This mpiece of cut rubber "flapped" in there as fuel passed it, making my guage read "bouncing" results, and my fuel pressure was always different from day to day. This "flap" was causing a restriction, and thus kept me from ever being able to adjust my fuel pressure down to a steady 5psi that my Edelbrock carb liked. I only finally discovered this by accident some 3 years after the fact when I was rerouting my fuel lines, and cut 2 inches off the end of that hose - for whatever reason I looked inside the cut off piece, and saw the "flap" in there - when I got everything redone correctly with 5/16 hose barbs, my issue went away instantly, and I waqs able to adjust my pressure anywhere from 10psi down to 2psi, and no bouncing guage.

Good luck!

 

Thanks - I agree and did the same thing with the fuel hose barb (yes it takes some determination but will go) so that will fix that.Every build I do I change all hose and bend pip so it will go away then I guess.It makes sense what your saying.I think your correct about the gauge bounce

OPSU - I can not go that route-I just cant.I am sure there is a extention or another 3 wire sensor but I want it dead if pressure drops or front end collision.Its a vert also and a lot of times key will be in position to use the electronics system with top down by remote control.If say like I take my wife to beach with friends we can listen to the sound system and I can use remote as I did with other motor plus I just feel it should be connected. If it comes to no other solution I will do your suggestion and thanks for the notes on how to do it I will save them but I would prefer it on there but just need to get past that heavy duty block hump over the oil filter.We have the same exact set up.

I really thank you for your help and I am sure you have corrected my gauge bounce problem as the interior glow shift pod gauges would adjust to the middle as it has and keep stable there as it has.I am sure there is a flap that makes sense.

Now can anyone help on how to connect the Oil pressure sending/switch unit on a gen 1 block ?

 

The OPSU DOES NOT stop the fuel pump in the event of a crash or low oil pressure. It ONLY runs the fuel pump in the event of an ECM/fuel pump relay failure. There is NOTHING in these cars that stops the fuel pump in the event of a crash or low oil pressure - that is false information. There was never anything developed until just the last 2-3 years that would cut power to fuel pumps in the event of a cdrash or low oil pressure, and those are only on very high end cars (like Lexus, Mercedes, BMW, etc.).

So there's no need at all to have a properly working OPSU.

In fact, there's several reasons to get rid of it ...

1) goes bad, fuel pump won't work
2) goes bad, fuel pump works ALWAYS regardless of key until battery is dead
3) expensive little bugger for all the trouble it causes ($40)

So, especially on a carb swap car, it's really best to get rid of the danm thing!