An RPV is a Residual Pressure Valve as Wilwood calls it, to keep a slight pack pressure on the rear wheel cylinders. I have a single Master Cylinder with 3/16 lines through the car which has a Girling system. It looks to me like they all have 45 deg. double flares. The flare nuts are longer than a similar fitting for modern inverted flare fittings (3/4" overall) and have 3/8" of thread with 1/8" un-threaded at the tube flare. They look like 3/8-24 to me but again, what standard... UNF, SAE or what?
Research on the Web gets pretty confusing and a bit contradictory on this subject. Hopefully, someone out there has the right answers... my head is starting to hurt!
Thanks,
Moe Morin
What do they mean slow of mind... I got target lock and was hung up on proportioning valves of some description and didn't think residual pressure valve. A wee bit ironic considering that I have a couple of the 2 lb Wilwood residual pressure valves sitting in my tool box from another project a few years ago. Oh well.
As far as the threads go, while there is a slight difference, Unified Fine and SAE threads are interchangable so that part of the set up is not really a problem. Where we get into issues are with the flares and and the fittings. The Wilwood RPV bodies are threaded 1/8-27 NPT as mentioned earlier being a pretty much a Wilwood standard. They can be supplied from Wilwood without adapters or with (or at least did at one time) a couple of adapters that would be used with your basic 3/8-24 fitting on an SAE 45º inverted double flare on a 3/16" (aka -3) tube. For our purposes we generally dispensed with the 45º stuff and used adapters for the AN 37º flares, but that was just a matter of choice since we were using AN stuff almost everywhere else.
My suggestion would be to consider taking the brake line to a local hydraulic shop along with the valve and which ever adapters you elect to use. Have them make you up a pre-bent tube or modify your existing tube with the RPV mounted where you want it to make it a plug and play operation. Around here I use a place called Royal Brass, I'm reasonably sure that you can find a similar type of operation in your area. A big part of their business is aimed at construction equipment and farming equipment so think in those terms if you are having trouble finding a place.
As for your exisitng flares, in the back of my mind I was thinking there were bubbles on the TR4A but from your description it seems not. Given that, my money would be on 45º flares as that is the SAE standard while 37º is more of an AN standard and used on some Japanese stuff from what I understand. If I had the tube here, I have tools to determine all of that, but this is also where that local hydraulic shop comes into play, they have tools to measure flare angles, thread pitch and thread taper if present. And remember if you do run across any British tapered pipe threads, they look amazingly like the US stuff, but the thread pitch is ever so slightly different. They're close enough to get each started on the other but different enough to screw things up if you force it.
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