Rear main oil return tube
 

I broke one off , flipping the engine around while installing pistons. It was tacked in place. I was able to get the broken threaded piece out easily. I went to see if I had some 5/16” ones on old caps. Found two with a ball check valve. Anyone know the “theory “ behind this??

Re: Rear main oil return tube
 

They were for grain trucks. They use to pick the front of the trucks up in the air, to dump the grain. The ball kept the oil from running out of the engine.

Re: Rear main oil return tube
 

Do not use 5/16 ones. If that is the size, bore to accept the newer 3/8's.

Look for other posts on the barn on how to do the complete job.

I have to leave right now.

Herm.

Re: Rear main oil return tube
 

Page 306 in the service bulletins. Thanks

Re: Rear main oil return tube
 

I agree with Herm: 5/16" is limited to the amount of oil flow it can handle. They have caused rear main leaks for me. I change all rear caps over to 3/8".
Good Day!

www.durableperformance.net

Re: Rear main oil return tube
 

I also change them to 3/8 Ford changed them to 3/8 because 5/16 is to small.

Re: Rear main oil return tube
 

3/8" gives 20% more flow than 5/16", FWIW.

Re: Rear main oil return tube
 

Hey George,
I realize that the tube thread (3/8) is peculiar. Other than not having right die, is there anything that you can think of , why a guy cannot make one ?
I just got a B block without the drain tube....and as things go last few years, can not locate much when needed/wanted in stuff pile :o !

Re: Rear main oil return tube
 

Actually about 50% more flow, since you square the radius and multiply by pi to find the area.

Re: Rear main oil return tube
 

That is interesting.....I'd like to see a picture!


.

Re: Rear main oil return tube
 

They still dump grain that way for the trucks without a lift.
Shorpy has lots of old pictures, or Google might turn up a picture.
Google "tipping truck to dump grain"

Re: Rear main oil return tube
 

You might use a pipe thread. It will work fine.

Re: Rear main oil return tube
 

Ok, thanks :)!
Hadn't thought of that .
I guess copper pipe would work, instead of steel as used by Ford.

Re: Rear main oil return tube
 

...

Re: Rear main oil return tube
 

Here is what I do ...There is more to it than 3/8 . Its the number of threads per inch if you need to fit a replacement drain tube to a 3/8 hole . I use a 3/8 by 32 threads per inch tap . This works with the drain tube threads that most model A parts venders handle. This is probably an uncommon tap . I got mine from Kodiak cutting tools www.amazon.com or www.kodiakcuttingtools.com . Brattons lists the drain tubes on page 44 and yes I have performed this proceduer many times .

Re: Rear main oil return tube
 

Purdy is probably correct about the 3/8 by 32 but I have found George Miller's suggestion works for me.

I use a 1/8" pipe thread tap and it always works. I spot weld the 3/8"steel pipe to the cap with stainless wire and find it holds well. I also drill out the oil passage in the cap to 3/8" when doing this conversion. Be careful, go slow, when the tip of the drill bit nears the back of the cap as the bit can bind in the grooves.

The tapped hole is not 90 degrees to the parting line of the cap. I built a jig from a cut-off of 10" structural "C" channel to position the cap to achieve the correct angle. If you place a 3/16" spacer under the front edge of cap with the rear of the cap on the bed of your drill press, the angle of the pipe will be correct. I use a 5/16" drill to prepare the cap for the 1/8" pipe thread tap and while the cap is in the jig, I use the drill press to start the tap to achieve alignment.
Photos below:
This jig is used for multiple functions...so ignore the other holes and knotches.

The bottom row of photos shows the procedure to enlarge the oil passage.
Remove galley plug with a punch...Drill passage with a 3/8" bit....continue drilling but don't drill out the back side. The last photo shows where to stop.
Good Day!

Re: Rear main oil return tube
 

very interesting. I have to pull the pan on my speedster as the oil plug is loose and just spins. while its out I think ill drop the rear main and do this upgrade

Re: Rear main oil return tube
 

Dave is right on. I also drill the oil passage also very important. You never know what you are going to find in that hole. Plus it fixes the tube from blocking the oil flow through the cap, if it is screwed in to far.

Re: Rear main oil return tube
 

I'd stay away from copper on this application. It might "work harden" from vibration and then crack and fall off. Why take a chance? Use steel and be done w/it.

Re: Rear main oil return tube
 

Good Jig, Dave.

Herm.