OK, Who knows master cylinders?

I'm plumbing brakes lines right now and the M/C I'm planning to use is from a Mopar Truck - (1" bore") Both reservoirs seem to be the same size. Which end goes the front discs and which to the rear drums? I'm also ***uming the correct rear cylinder would have a factory residual check valve built in. Looking at a Horton Street Rods catalog it seems the end farthest from the pedal rod is the front brakes. I know we've talked about this before but just cn't seem to get it right in my head. Need some help here

 

is the cylinder for a disk brake truck?

how big are the reservoirs? (inches long x wide x deep)

 

Ok admittedly I don't know squat about Mopar Master cylinders, but what little I do know might apply so here goes nothin'......

***uming you have a Disc/Drum master the Disc Brake reservoir will be the LARGER of the two (the reason is because as your disc caliper wears and more importantly the size of the disc brake piston is rather LARGE as in it displaces a LOT more volume than when the drum shoes wear since your rear wheel cylinders are probably some where around 1" or 1-1/8" or so in diameter where as your dics brake piston is 2 or 3 times as big. Bigger piston needs MORE VOLUME of fluid.

In YOUR case - you suggest both bores are the same size ..... hmnnnn sounds liek maybe you have a drum/drum master or even a disc/disc master (if Mopar even did such a thing). You might want to look into that a tad further to be certain it is appropriate for your aplication.

Mopar - I dunno for sure - but alot of GM master cylinders have the PRIMARY side as the one closest to the pedal (usually referred to as the REAR reservoir) and that normally goes to the FRONT brakes. Of course I don't think this is a "rule of thumb" across all manufacturers. The next consideration or "giveaway" is the brake line diameter - usually the larger diameter fitting goes to the DISC brakes - that volume thing again.

Residual Pressure Valves are typically NOT built into the "older" style inline dual bore master cylinders. Instead they are part of the combination valve (proportioning valve) - I have also seen the rear RPV built into the rear "T" fitting. Granted some of the "NEWER" style Master Cylinders do have the RPV's built into the EXIT fittings of the master- these are easily noted since they are screwed into the master.

I am sure I will be corrected, but I have only seen the RPV's built into the SINGLE reservoir masters (new fangled stuff aside) - so It sounds like you may also need a combination/proportioning/metering/RPV valve.

Of course I am speculating on several things since I cannot see your stuff and if you have any doubts - pull it apart and verify it!!!

 

Thanx. This is from a disc /drum application - 2000 Dodge van (1500 series, I believe) What I like about it is the fact that it's aluminum and I won't need to paint it and try to keep the paint in place. 0 never had a M/C that wasn't cast iron that seemed to bleed enough fluid through the casting to eat all the paint off. There is a difference in the size of the adapters but both lines are 3/16".

 

OK - what I am picturing now is a "skinny" late model aluminum master with the plastic reservoir on top. These can get pretty funky - possibly having IN LINE proportioning valves - RPV's and who knows what else. I can't be of much help there - outta my comfort zone. But I will say this - the fittings are different size because they MATTER which goes where!!! Look closely at the plastic reservoir on top - it's likely that the REAR section has more VOLUME than the FRONT section - if this is the case then the REAR section gets plumbed to your DISC brakes - just like the "old" stuff.

Since that's such a common vehicle - maybe find one (friend or friendly stranger in the local parking lot) and have a peek under the hood. Only take a minute and you'd get that warm and fuzzy feeling that you have it right. Maybe even a Hamber drives one and would snap a pic for you. Just thinking out loud.

 

If it's for a disc brake application, and both reservoirs are the same size, then it really doesn't matter which line you connect to front or back. They both get the same pressure to them.

I doubt there's an RPV in the m/c, being so new. They did have them built in back in the 60s with drum brakes, before the federal requirement for an idiot light came along in 1968, at which time they started putting all that stuff in the combo valve.