[RocktimusPryme]

Sanity Check me here.

So one of my projects has an external wet sump oiling system. Meaning the Oil is still stored in a pan below the block like normal, but the pump is an external cog belt-driven job. Probably not a decision I would have made, I took over someone elses project. But they spent like $2000 on really nice parts between the pan and pump and all so we are rolling with it.

I recently first fired it, everything works. Roared right to life and surprised me on camera, honestly, but I am terrified of the prospect of that belt breaking or otherwise coming off and killing the engine because it doesnt have anything pumping oil. So I want to wire in a low PSi (Like 2 or 5 PSI) cutoff switch that will kill the engine if there is no oil pressure.

Something like this.
https://www.stewartwarner.com/produc...witch-sw76061/

Almost all of these switches are marketed as fuel pump cutoff switches. (See attachment) But it seems to me that if the engine was allowed to run until all the fuel in the bowls on a holley were empty that would still be plenty of time to hurt an engine with no Oil Pressure.

So couldnt I just use one of these switches. Where the Common (C) port on the switch going to the ignition coil, Battery to Normally Closed (N) and Keyed Power to the Normally Open (NO) to kill spark in a no pressure event vs kiling the fuel pump?

I might have to hold the key on crank for a touch longer to build pressure before it starts, but thats fine.

[hojs69]

There was a gent posting here with the attached system. I cannot find the Post right now.

[RocktimusPryme]

Thats interesting. I couldnt find their product via Google. Im assuming its programable since its just using an oil pressure sending unit, rather than a switch like the one I posted.

Im not running an MSD setup on this car. I honestly think if I just run the wire that would normally go straight to the coil from the keyed ignition, through one of those switches I posted it should work.

[chiphead]

That diagram is missing the wire between the keyswitch start position and the starter solenoid.

How about wiring it to an idiot light? That way if the oil switch fails or you lose oil pressure, it doesn't kill the car on a railroad track or in an intersection?

If you want it to kill the ignition, you'll need to wire it between the key run power and the ignition coil. A separate bypass wire would be needed for starting because there is no oil pressure at start. Pretty much exactly how pontiac wired their ignition systems to bypass the points resistor wire during crank.

It may cause some annoying fail to starts if there is no oil pressure when it fires and you let go of the ignition. Which is why the switches are sold for control of a fuel pump or a warning light.

I had one of those exact switches on my other 67 when I had a Comp 140 fuel pump and nitrous. If the engine stalled, it cut the fuel pump so it wouldn't risk drowning the Q-jet. I had a manual override switch on the dash so I could bypass the pressure switch, if I wanted to run the pump with engine OFF or I was spraying. Don't want the ole piston-melter 5000 if the fuel goes away but the nitrous doesn't.

[Dragncar]

I have a Vega oil pressure switch that controls 2 relays. One to my fuel pump and the other to my MSD box.

[Squidward]

If you had concerns about cranking while you build pressure, you could always use the R terminal on the starter to bypass the oil relay when you crank. Kinda like bypassing the points resistor wire that you don't have.

I need to do something similar, but something to kill the fuel pump. I have an impact switch for cutoff of the fuel pump if I get in a wreck, but I haven't hooked it up yet.

[RocktimusPryme]

Originally Posted by chiphead

A separate bypass wire would be needed for starting because there is no oil pressure at start. Pretty much exactly how pontiac wired their ignition systems to bypass the points resistor wire during crank.

It may cause some annoying fail to starts if there is no oil pressure when it fires and you let go of the ignition.

I considered the start bypass part, and thats why I was eyeing switches at very low pressure points. In my case, specifically because of the external pump, I dont think that will be an issue. The one benefit I have noticed is that damn thing generates like 65 PSI no matter the speed its spinning. When I put my slow air ratchet on the front of it, it generates that much. BUT there can be a delay because it has to prime through like 6 feet of AN hose. And this engine lights off FAST.

So me having to crank it a little longer to prime those lines before the switch closes and allows spark I would consider more of a feature than a deterrent. If I watch the oil pressure gauge there is a short hesitation between the engine lighting off and pressure coming up on the guage that I dont love. Part of that may have been that I was using a cheap mechanical gauge with a long plastic tube vs an electronic sending unit for first start up.

I was consdiering wiring a manual switch to kill spark, specifically to allow me to crank the engine until I could see oil pressure before I started it. This might kill two birds with one stone. I guess its not that much money or difficulty in wiring. I could just try it and report back.

The Vega switch thing is interesting because they are cheaper. Would be easier to have a backup in the glove box. I was trying to find some information on the pressure set point of the switch but Google didnt give me a number in my short look.

[MatthewKlein]

I use relays and an oil pressure switch ment to operate an electric choke.

Distributor is powered by a relay tripped by the choke switch

Separate relay powers the Distributor and starter while cranking

[zippy]

Originally Posted by RocktimusPryme

I considered the start bypass part, and thats why I was eyeing switches at very low pressure points. In my case, specifically because of the external pump, I dont think that will be an issue. The one benefit I have noticed is that damn thing generates like 65 PSI no matter the speed its spinning. When I put my slow air ratchet on the front of it, it generates that much. BUT there can be a delay because it has to prime through like 6 feet of AN hose. And this engine lights off FAST.

So me having to crank it a little longer to prime those lines before the switch closes and allows spark I would consider more of a feature than a deterrent. If I watch the oil pressure gauge there is a short hesitation between the engine lighting off and pressure coming up on the guage that I dont love. Part of that may have been that I was using a cheap mechanical gauge with a long plastic tube vs an electronic sending unit for first start up.

I was consdiering wiring a manual switch to kill spark, specifically to allow me to crank the engine until I could see oil pressure before I started it. This might kill two birds with one stone. I guess its not that much money or difficulty in wiring. I could just try it and report back.

The Vega switch thing is interesting because they are cheaper. Would be easier to have a backup in the glove box. I was trying to find some information on the pressure set point of the switch but Google didnt give me a number in my short look.

Same with me. Mech Oil gauge, taken from by the dizzy. Engine starts right away, but takes couple seconds for pressure to register. Kinda freaks me out. But is cranking vs the first couple seconds running any actual difference for engine/bearing wear? With low to no oil press.