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H2OSB
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Joined: April 14, 2013
Posts: 1559
Location: Modesto, CA
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 Posted: Mon Feb 17, 2025 4:09 pm Post subject: Re: Oxyboxer (s) for my Ghia project |
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I'd love to put a 76mm WBX crank in a T1, but I don't know if I have the intestinal fortitude to go beyond that.
H2OSB
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BFB
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Joined: November 03, 2014
Posts: 3143
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| Posted: Mon Feb 17, 2025 7:58 pm Post subject: Re: Oxyboxer (s) for my Ghia project |
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I really want to build an oxy so i can use 104 pistons on a “T1” , i have two 1.9’s , wish at least one was a 2.1 so i had the 76 crank though.
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halbug
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Joined: March 09, 2006
Posts: 579
Location: Germany
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halbug
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halbug
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vince1
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Joined: December 14, 2003
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halbug
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halbug
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Ian Godfrey
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Joined: September 25, 2006
Posts: 1216
Location: Melbourne Australia
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| Posted: Thu Mar 06, 2025 1:47 pm Post subject: Re: Oxyboxer (s) for my Ghia project |
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Very Porsche 
Are you using a drain back valve to stop the crankcase filling overnight? |
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Glenn 
Mr. 010
Joined: December 25, 2001
Posts: 80499
Location: Sneaking up behind you
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| Posted: Thu Mar 06, 2025 2:15 pm Post subject: Re: Oxyboxer (s) for my Ghia project |
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Just saw this topic... very cool and i'll be following it.
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עַם יִשְׂרָאֵל חַי |
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Dan_Lockwood
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Joined: October 03, 2023
Posts: 469
Location: Clare MI
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| Posted: Thu Mar 06, 2025 5:18 pm Post subject: Re: Oxyboxer (s) for my Ghia project |
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| Ian Godfrey wrote: |
Very Porsche
Are you using a drain back valve to stop the crankcase filling overnight? |
I'm guessing a "drain back valve" is used when the setup has an external oil cooler that is located above the sump. I've never heard of a drain back valve in this genre.
I know my old Harley Shovelhead had an oil tank under the seat and over a period of say two weeks, the crankcase would wet sump and fill up with oil that had drained through the oil pump in some manner.
In my case I have a full flow oiling system setup. The oil is pumped from the oil pump up and through my oil filter. From there I have it routed up to the overhead fan based oil cooler. But prior to the cooler, I have a bypass thermostat that routes say 90% of the oil directly back into the motor until the thermostat sees 180 degrees in the oil. At that time the thermostat opens up and allows full flow up through the cooler and back into the oil galley.
I've wondered if the oil would drain back from the cooler and how one might go about stopping that, short of putting in 1/4 turn valves, or the like. My thoughts are that the oil pump itself will be very tight and allow very little oil to leak back through the gears and into the sump. But the return line going to the oil galley, would have just the resistance of the bearings to stop the drain back.
What am I missing and should even be concerned about it?
Sorry to hijack this thread... 
Dan |
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Ian Godfrey
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Joined: September 25, 2006
Posts: 1216
Location: Melbourne Australia
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| Posted: Thu Mar 06, 2025 10:22 pm Post subject: Re: Oxyboxer (s) for my Ghia project |
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Dan, a lot of people think this is fixing a problem that doesn't exist. Turbo 911's first had them i believe. The idea was the tank was higher than the sump and over 'time' the oil drained through the pump into the sump and they could be quite smokey on start up. The Porsche ones are expensive so this one is popular
https://willhoit-auto-restoration.mybigcommerce.co...p-to-1989/
and the expensive Rothsport
https://rothsport.com/collections/oil-inlet-check-valves
I have never worried about the small amount of oil in a cooler/filter draining back, it's when you have maybe 7 quarts in a dry sump tank  |
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halbug
Samba Member
Joined: March 09, 2006
Posts: 579
Location: Germany
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| Posted: Thu Mar 06, 2025 11:43 pm Post subject: Re: Oxyboxer (s) for my Ghia project |
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| Dan_Lockwood wrote: |
| Ian Godfrey wrote: |
Very Porsche
Are you using a drain back valve to stop the crankcase filling overnight? |
...
What am I missing and should even be concerned about it?
Sorry to hijack this thread...
Dan |
Dan, Ian, I am so glad you are raising this subject, so no hijacking at all! I have been pondering this back and forth myself and have not come to a final result.
In my case the scavenge pump will route the oil from the engine sump through a thermostat into the external tank. If the oil gets hot, the thermostat will direct the oil to the front mounted oil cooler first and then into the tank. The tank filling inlet is at its highest point, so no oil can escape through there.
The tank's outlet to the pressure pump is at a low point to positively feed the pump. And this could become an issue, because if all the oil would seep through the gears, over time, the engine would suffer from starvation on start up.
My first idea was to use a motorized ball valve in combination with a starter delay relay, to make sure the valve has fully opened before the engine starts. I have no room to install such a valve and the delay complicates things further.
Second idea was to use a ball check valve, maybe operated by a bowden cable from the interior of the car. Also here, I would want a dead switch or at least a warning light combined with the closed valve. There is very! little space left in the inner fender, so even this solution could become rather complicated in my case.
Right now I was about to test what the oil level in the engine will be once the oil from the tank drains into the case. I figure that anything below the crank cheeks would be save for starting the engine. More important, will there be any oil left in the tank when starting up???
The valves Ian mentioned are one more option I guess...
Thanks for the great discussion guys!
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Ian Godfrey
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Joined: September 25, 2006
Posts: 1216
Location: Melbourne Australia
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| Posted: Fri Mar 07, 2025 12:48 am Post subject: Re: Oxyboxer (s) for my Ghia project |
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Lars and Dan, I thought about a ball valve as my tank is where the back seat was and i can reach around to it. So I thought about putting a HUGE red tag on my key ring 'OPEN OIL VALVE', but i can be absent minded 
I also though about an ignition interlock or a fuel pump interlock but a passive anti drain back valve is 'absent minded' proof.
My tank is higher in the car than yours, so more of a problem.
I think working out how much might drain in to the sump is a good idea, ideally, you would want the oil level in the sump to be below the pushrod tubes so the rocker covers didn't fill up and certainly not above the crank centre line.
That would be a lot of oil in the sump and not much in the tank. |
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halbug
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Dan_Lockwood
Samba Member
Joined: October 03, 2023
Posts: 469
Location: Clare MI
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| Posted: Fri Mar 07, 2025 5:32 pm Post subject: Re: Oxyboxer (s) for my Ghia project |
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| halbug wrote: |
| Dan_Lockwood wrote: |
| Ian Godfrey wrote: |
Very Porsche
Are you using a drain back valve to stop the crankcase filling overnight? |
...
What am I missing and should even be concerned about it?
Sorry to hijack this thread...
Dan |
Dan, Ian, I am so glad you are raising this subject, so no hijacking at all! I have been pondering this back and forth myself and have not come to a final result.
In my case the scavenge pump will route the oil from the engine sump through a thermostat into the external tank. If the oil gets hot, the thermostat will direct the oil to the front mounted oil cooler first and then into the tank. The tank filling inlet is at its highest point, so no oil can escape through there.
The tank's outlet to the pressure pump is at a low point to positively feed the pump. And this could become an issue, because if all the oil would seep through the gears, over time, the engine would suffer from starvation on start up.
My first idea was to use a motorized ball valve in combination with a starter delay relay, to make sure the valve has fully opened before the engine starts. I have no room to install such a valve and the delay complicates things further.
Second idea was to use a ball check valve, maybe operated by a bowden cable from the interior of the car. Also here, I would want a dead switch or at least a warning light combined with the closed valve. There is very! little space left in the inner fender, so even this solution could become rather complicated in my case.
Right now I was about to test what the oil level in the engine will be once the oil from the tank drains into the case. I figure that anything below the crank cheeks would be save for starting the engine. More important, will there be any oil left in the tank when starting up???
The valves Ian mentioned are one more option I guess...
Thanks for the great discussion guys! |
I have a slightly different schematic that is basically what's below. I have a MasterLube pre-luber accumulator tank with a 2qt capacity.
In the bottom of my air over oil accumulator tank, there is an electric solenoid valve that is triggered by a spring-loaded return switch in the sand rail. When I turn on the key and switch, I soon will see oil pressure, at that point I know I'm okay to start the motor. BUT... it may take some (lots) of the oil out of the accumulator so it's now maybe close to empty. After the motor starts and builds oil pressure in all my lines and oil gallery, the solenoid valve is also a one-way check valve. It will let oil re-accumulate back into the tank automatically until the air pressure over the oil is equalized with the normal oil pressure in the oil system.
How does the Porsche drain-back valve work. Obviously it's a one-way valve of sorts. Is there a ball and seat with the ball being held against the seat with a very weak spring that will stop the gravity oil getting through, but actual oil pressure of, say 3 psi, would override the spring and let a full flow of oil as if without the valve in place????
In this system, with the opportunity for the oil cooler oil to slip past the bearings and back into the sump, and or, the filter oil/cooler line can also seep back into the sump via gears in the oil pump, where would you place the drain-back valve?
Thanks for the added discussion on this subject... 
Dan |
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halbug
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halbug
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TRS63
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halbug
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