Pressure Fed Conversion

[Charles P]

How have people tackled the blanking off of the oil gallery to the redundant jets when fitting a pressure fed crank? Blocking the jets is easy enough but I'd like to stop flow of unfiltered oil along this gallery. The screw in blanking plugs in the crankcase are inconveniently out of line with the cast main gallery so the idea of simply screwing in a blanking plug seems impossible because I can't get a tap in to create a female thread. 


Suggestions welcomed


Thanks

Charles

[Robert Leigh]

I have not done a pressure feed conversion, but I have fitted external filters which require half the process you need. I removed the plug in the flywheel housing at the back of the gallery and using the existing thread as a guide and using a taper BSP tap I threaded the back of the gallery. It can then be plugged with a standard BSP plug loctited in place. I cut off the square on my plug and cut a screwdriver slot. The taper threaded plug will form a good seal in the taper threaded gallery, especially with loctite in the thread. Because I have been feeding the oil into the front of the gallery to the jets I have not needed to plug that end, but I believe the same technique will be satisfactory.
Robert Leigh

[Chris KC]

Pretty much what Robert said.

Rear end of the jet gallery tapped (I'm struggling to make up my mind about the one on my bench at the moment, it's either 1/4BSP parallel or 1/2" UNF) and a plug screwed in to a depth of about 40mm measured from end of gallery to head of plug. This gives it clearance to the oil pressure gauge take-off on top of the case, which is similarly over-bored and tapped to take an elbow connector with 3/8" spout (you can add a new oil pressure gauge take off on top of it - 1/8" BSPP I think - just a matter of finding a suitable stack of fittings). An NBR fuel hose runs from this spout to your oil filter. My preferred filter position is mounted on the body, on the same level as the oil gallery.

The next bit depends how you plan to arrange your pressure feed. Mine is from the centre main bearing, so the hose re-enters at the front of the gallery via a screw-in in-line hose connector, similar to Robert's I guess. If you are feeding from the front end you will have to re-enter accordingly.

[jansens]

Not for a pressure fed engine but so I could fit an oil filter but I did more or less what Chris said. A plug inserted from the rear about 1.5" long. It was a tight fit but I also used a screw through from the side to hold it.

I mounted the filter on a bracket hung off two of the head studs. And I used hard cupro-nickel lines to connect it, one coming up from the oil gauge hole (over bored and tapped as Chris mentions) up to the filter then another going down on an angle and looping around the dynamo to re-enter the front of the engine. I was going to use the front side hole to provide a take off to the oil gauge but there is no room for a fitting as the radiator hose is in the way. I ended up using a blanking plug there and making a T fitting in the top of the inlet pipe to the filter and taking the oil gauge line from there.

My original thought was mounting the filter to the firewall but then you need to allow for movement between the engine and the body either by using rubber hoses or having vibration loops in the hard lines. With it mounted on the engine you can remove the engine without having to undo all the oil lines.

Simon

[Charles P]

Thanks gents.
Just need to be more audacious in tapping into the dark and unknown. I had a look inside with a usb endoscope on my phone and the suggestion looks doable. The thread is 1/4 BSP so I'll tap it, clean it very well and use a 1/4 bsp blanking plug smeared with JB Weld, driven in with a long allen key.

Charles

[Chris KC]

Not sure if these add much to your understanding but here are a couple of pics.

Charles, I think if you use epoxy as described it will come off on the threads in the oil gallery before the plug reaches its final resting place, and thereafter slowly flake off into your oil (albeit on the right side of your new filter). I would suggest dabbing a bit of Loctite into the oil gallery through the (now enlarged) oil pressure gauge hole, just before the plug passes it by.

n.b. if the elbow hose fitting protrudes even slightly into the gallery thread then the plug can't possibly come out past it anyway.

   

   

[Robert Leigh]

I think all the oil system threads are BSP; I had wondered about UNF which is very close at that size, but not the same.
Robert Leigh

[Chris KC]

Inclined to agree Robert, but the specific engine I'm working on comes up 20 TPI every time I check it (whereas BSP is 19 I believe). I'll test some known BSP / UNF fixings in the thread as soon as I can lay my hands on some.

[dickie65]

I am just about to convert a Nippy Crankcase to pressure fed crank.
I will be blanking the oil jets ( Probably with alumiweld )
I am going to use the oil gallery as a feed to the front of the engine as per the pressure fed engine.
I am happy to let the front Camshaft bearing have unfiltered oil. I will just change the oil a bit more often.
I will be making a custom camshaft front bearing with external O rings and a smaller oil feed,
I will be using a reground standard camshaft as well.
I will filter the oil from the front of the gallery before it is fed into the nose and then the crank.
I have been running a Pigsty Conversion for the last 20 years and I am after a more original looking engine bay.
This will make working on my engine easier as the oil filter housing mounts on the head studs and is a Pig to remove to get the head off to deal with valves etc.

My current system just has a blanking plug at the rear of the gallery, the oil comes out of the oil pressure gauge port which is now 1/4 bsp
then into a filter housing and the pressure relief valve manifold and back into the front of the oil gallery, and into the nosepiece the overpressure goes into a tapped 1/4 bsp hole in the front of the crankcase facing backwards away from any moving parts inside the engine.
It all works well but looks horrible with 3 x 3/8 armoured hoses at the front of the engine.

I am with Chris do not use JB weld. Loctite make a few suitable products which can be used on all your oil line fittings
( your engine is worth it )

[Steve Jones]

I've always thought BSP. It sort of fits with what you'd expect (I do understand about Austin and threads though ). In any event, would Austin have really used a UNF thread in the 1920's? Whilst it did exist, sort of, it wasn't, really used worldwide until post WW2. I do agree that Loctite on the threads will work better than an epoxy putty when it comes to sealing. Even a couple of turns of PTFE tape would do the job better.

Steve