3/4" master cylinder?
- Thread starter Icetech
- Start date
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Inertia
Well-Known Member
There is a Toyota 3/4, 13/16 and others that have a very similar 4 bolt pattern.
Slotting the holes worked for me.
I'll dont know number off hand,
Try 70's Toyota m/c images, truck seems likely.
I get a pic later.
Slotting the holes worked for me.
I'll dont know number off hand,
Try 70's Toyota m/c images, truck seems likely.
I get a pic later.
Icetech
Well-Known Member
will take a look.. more worried bout finding something that will work with the stock pushrod, or at least has the groove in the MC to keep it in place.
Wish i had never converted to disc.. this has been a wasted summer and like $1k wasted on this crap already. Drums would have worked perfect.
Inertia
Well-Known Member
Some of the m/c have retainer C-Clip, some not.
I often just weld a flat washer to a piece of rod, put washer about an inch from master (weld rod to close structure) - as a guide so if it comes out, guide holds it in alignment with m/c. (Std racecar mod)
Keep in mind the Mopar brake lite switch limits the amount of pedal return, - without force .
I often just weld a flat washer to a piece of rod, put washer about an inch from master (weld rod to close structure) - as a guide so if it comes out, guide holds it in alignment with m/c. (Std racecar mod)
Keep in mind the Mopar brake lite switch limits the amount of pedal return, - without force .
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Icetech
Well-Known Member
yeah, i'm just paranoid...
My issue is..i have 1000psi at the MC, 1000at the dist block.. 1000 at the connector to the soft line to the front calipers (been months of fighting this.. bought a gauge) BUT.. at the caliper bleeder i have 650psi and the car from like 30+ is scary to stop.. it's like the brakes won't bite into the rotors...
I have replaced everything in the system like 3 times now other than the calipers.. they might go next.
Have heard that front discs take 3000 psi and rear drums take 300 psi.
Had success with the 15/16" manual brake master, fitment for 1973 Dart Disc/Drum.
People are having good luck with the master cylinders Dr Diff is recommending. Kind of like a Dodge Dakota or Dodge Caravan master.
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Had great results on a '69 Satellite drum/drum car going to a 15/16" manual master.
Much more gradual control, and less pedal pressure. Was very happy with that compared to the stock master.
☆☆☆☆☆
Had success with the 15/16" manual brake master, fitment for 1973 Dart Disc/Drum.
People are having good luck with the master cylinders Dr Diff is recommending. Kind of like a Dodge Dakota or Dodge Caravan master.
_________
Had great results on a '69 Satellite drum/drum car going to a 15/16" manual master.
Much more gradual control, and less pedal pressure. Was very happy with that compared to the stock master.
☆☆☆☆☆
Icetech
Well-Known Member
i'm using a drdiff 15/16 already.. have tried 3 different master cyls.. been fighting with this all summer. Everything i read says 1000psi for front discs.. but i can't get over 650 at them.
Rotors and linings must have proper surfaces to make friction. If new, was prep required by the mfgr? Sorry, just only thing I could think of. Good luck
Icetech
Well-Known Member
rotors were new.. just cleaned and used.. nothing said about prep.. and i had the stock pads on that came with the kit.. then upgraded to EBC yellow stuff pads.. which are a bit better.. but it's bad enough that i don't think i could lock the fronts on gravel.
Inertia
Well-Known Member
Whatcha got for calipers, number of pistons and diameters ?
Rear reservoir is for the front discs, front reservoir for the rear drums.
Want to have the correct disc/drum proportioning valve and not using the stock drum/drum valve.
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Icetech
Well-Known Member
They are stock type mopar slider calipers 1 piston 2.75"..
Whoever told you those numbers is a person that needs a punch to the face.
Icetech
Well-Known Member
Lines are in the right orientation.. and am using a wilwood proportioning valve..
The main issue is the pressure drop within 14" of line.. it's just weird.. the common denominator is the calipers but it doesn't make sense... hoping drdiff gets some 2.75s in stock and i will replace these just to be sure.
Inertia
Well-Known Member
Something's whacky, as you know.
Pressure should be same at bleeders.
Whatcha using for soft hoses, if you have old hoses, maybe try those.
I've had hoses do some pretty gucked up things, but not reduce pressure unless they're expanding, even so . . . Pressure should "catch up" . .
Hmmmmm
Icetech
Well-Known Member
the hoses are the braided ones drdiff sells.. i think they are a later model GM hose... I replaced the ones that came in the kit with them, just to rule that out also..
jos51700
Green Bearing thread connoisseur
First, this is why I'm a fan of using stock parts for a daily. Everything usually just....goes together, without much drama. If the assembly line people can build it, so can I.
Second, this isn't adding up. You say you're losing pressure within the first 14"...what is 14" from the master that you're measuring that at?
It sounds like an air issue (are you bench-bleeding the masters?) or something in the line that's obstructing flow but not staying 'fixed' in the system, like a floater of debris.
Kinda the whole point of using hydraulics is that the pressure is uniform throughout the system. From a physics standpoint, it damn near has to be. If you're measuring X pressure at one point, it'll be X somewhere else, and a pressure increase at point A is pretty much instant anywhere in the system. This really points to another issue.
Second, this isn't adding up. You say you're losing pressure within the first 14"...what is 14" from the master that you're measuring that at?
It sounds like an air issue (are you bench-bleeding the masters?) or something in the line that's obstructing flow but not staying 'fixed' in the system, like a floater of debris.
Kinda the whole point of using hydraulics is that the pressure is uniform throughout the system. From a physics standpoint, it damn near has to be. If you're measuring X pressure at one point, it'll be X somewhere else, and a pressure increase at point A is pretty much instant anywhere in the system. This really points to another issue.
Icetech
Well-Known Member
It is all stock parts other than the proportioning valve which has no effect on the fronts...
And yeah.. i get the hydraulic system thing which is why this is making me nuts... unless something is making pressure drop it should be the same across the system...
At this point i think it has to be the calipers.... i hate to buy another set and get the same thing. i'm sure they are all probably made by 1 place now. will wait and see when i get some.
Odd thing though.... both calipers with the same pressure drop... odds of that are soo low.
jos51700
Green Bearing thread connoisseur
I looked at your photos/thread on FBBO.
It looks like you have an adjustable pressure regulator....but it's on the [physically] rear line on the car. If so, wouldn't that be the front brake system? It's really hard to see in your photos, so I'm not sure.
That adjustable pressure regulator needs to be in the rear brake system if it's not. It's there to limit pressure to the rear system so they don't lock first, which would cause the car to swap ends. I always saw them under the car, or at the rear.
It looks like you have an adjustable pressure regulator....but it's on the [physically] rear line on the car. If so, wouldn't that be the front brake system? It's really hard to see in your photos, so I'm not sure.
That adjustable pressure regulator needs to be in the rear brake system if it's not. It's there to limit pressure to the rear system so they don't lock first, which would cause the car to swap ends. I always saw them under the car, or at the rear.
jos51700
Green Bearing thread connoisseur
Are you BENCH-bleeding the master? but see my post a minute ago.
Icetech
Well-Known Member
The valve is going to the rear brakes.. and the MC was bench bled.. sorry i missed that...
And thanks for the help guys...
jos51700
Green Bearing thread connoisseur
Have you tried pulling the valve out of the system, bolting the lines up solid, and driving it?
It looks like there's a junction block down there. Is it an actual junction block, or is there something in there that separates the front and rear systems?
I don't know the in's and outs of getting rid of the single-pot master, but I seem to remember something about that junction block needing to be updated too?
Have you tried capping the rear line and ONLY running the fronts?
Icetech
Well-Known Member
It's just a block.. if you use the block and a prop valve just for the rear you don't need a normal oem prop valve. And the rears shouldn't effect the pressure of the front.. but i am going to play with that, who knows.. i can block it off easy enough
jos51700
Green Bearing thread connoisseur
Wait, are you saying that you have the front and rear lines hooked together at that junction block?
If so, the systems would function as one. Which would include that adjustable pressure bit.....which reduces line pressure.
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