62 Impala ...changed from a single to a dual master ( power brakes)....can't get any REAL front brakes (rears lock up EASY)..... anybody know for sure which the front chamber feeds ?? the front or rear brakes (ALL DRUM ) ???? Like front chamber on master feeds front brakes or does the REAR chamber on master ( closest to the firewall when installed) feed the front brakes ?? HEEELLLLP !! jersey skip
Couple of idea's for you: 1) The larger of the two bowls are the front brakes 2) The larger bowl is normally closest to the firewall when mounted in your Impala on the firewall 3) You may need a proporationing valve for the REAR brakes if the rear tires are locking up before the front brakes, ***uming you have the brake lines hooked up properly. 4) I remembering reading an artile regarding using a dual master cylinder on four wheel drum brakes, however; I can not recall exactly what the article stated. You may want to call one of the better after market brake companies if you still have the problem. I think the article related to certain master cylinders to be used on four wheel drum brakes, but don't rely on this as I stated, I can't remember....
Bowls are the same size ......... no valve is necessary in an all drum system .... anybody know which chamber feeds what FOR SURE ??? thanks, jersey Skip
I used to have a '64 Impala SS that I switched from a single master to a dual. As I remember, under hard braking it would lock the rears up first. I was using a drum/ drum master. I think I had the rear chamber feeding the rear drums. If that's the way you have it set up, try switching them around and see if it makes any difference. Otherwise, you may need to get one of those adjustable prop. valves.
Wrench ...Are you SURE the back brakes went to the rear chamber ( PITA for me to change now).....an all drum system will Always favor rear lockup any how but this car just DON'T stop ........at 10 MPH it'll drag the rear wheels for 20 feet before it stops with the pedal nailed HARD .... jersey Skip
Ok.. based on what I know.. please look at the attached diagram. Based on the weight of these old vehicles, it's easy to lock up the rears. It is possible to change that, using valves, but you have to be careful not to set the valves too tight, otherwise pressure stays in the lines, and you end up riding your rear brakes, which causes overheating, squealing, bearing problems, etc etc etc. But when setup properly, proportioning valves should solve most problems. Remember that when you hit the brakes hard, a big vehicle actually leans towards the front... called Plowing. That takes weight off the rear brakes, which allows them to lock up faster. If you can put more pressure on the front brakes, and less on the rears, it is less likely that the rears will lock, but nothing short of disconnecting the rear lines will stop that 100%. And I don't reccomend doing that... although it's fun for burnouts.... Make sure you're lined properly, try the proportioning valves, and experiment a bit. I find that about 60x40, front rear, is about perfect for my big old caddy. But I aint tryin to stop on a dime with these coker www's, there friggin expensive, and I don't like scrubbin em down while stoppin, so I take my time stopping. In an emergency, IT'll stop just fine, but may lock the rears, actually with the new dual setup I plan on, It should lock all 4 with no problems. Have fun, be careful, and keep in rollin man.
It was about 10 years ago, and I'm not sure just how I had it set up. I know that it would stop fine. It was just under hard braking that it would lock up the rears.
Wouldn't call a duel chamber "power brakes" w/o the booster, but I'd follow the diagrams above...in the worst scenario, get a buddy, and bleed them from the furthest out, the closest...I.E. p***enger rear, driver rear, p***enger front, driver front...the bowls ARE NOT the same size...one's deeper than the other. You'll have to drain off the brake fluid to see the depth correctly. Try a fresh restart with the information given. Repost w/ results. Note: Do not try this in traffic. hehehe
back to basic drum brake tech drums turned to many times... shoes spread only/ travel so far you know. have the shoes on correctly one is longer(rear shoe) check your book!! adjust free spinning wheels adjuster until it slows/grinds noise then backoff 1 click should not be draggin the pedal piston goes thru the front wheel's resisvior first and the rear brakes last all cars ever made? bleed as stated do not let the resisvior empty and have the cover on tight to bleed do not reuse bled out fliud discard it do you have radicly dif wheel/tire sizes ... could account for rear lock up first new or used dual cylinder???? pinch the front line trying to fit it in a new place??? should it have a booster some need them to work start with a check of each wheel/ all parts first for correctness old wheel cylinders stick so be sure they travel as needed in out see why people have disc brakes now they are a no brainer.. good luck paperdog
Car HAS power brakes....... chambers are EXACTLY the same size ..... car had a SINGLE master and NO valve .....been thru ALL the basics and I'm usin' a PRESSURE BLEEDER ..... car is all ORIGINAL ( 'cept for the dual master now) so discs are out ........I've done many PITA streetrod systems and NEVER had this kinda' problem ...... it SHOULD be plumbed right as far as the "net" chevy guys say ( rear port to FRONT brakes)...I'm gonna try reversing the ports and see .........any one ABSOLUTLY know which chamber feeds which system ??? And thanks guys for the suggestions..... jersey Skip
What was the donor vehicle for the new master? I used a vette 1" and the front port goes to the front brakes. I had them reversed, and it acted exactly the way you describe. switched the ports, and Bob's your uncle.
1967 Impala master .......... man .... I 'll try switchin' the ports....and i hope BOB is still in the family ! Jersey skip
Dual circuit master cyclinders for drum/drum applications normally have two indentical sized chambers. Every GM I have ever seen or worked on had the chamber closest to the firewall routed to the rear and the other, front chamber, going to the front brakes. I don't think a metering and/or proportioning valve is needed in a drum/drum vehicle. At least if it has the same size drums and rolling stock on both axles. Residual pressure valves are used for drum/drum, but are part of of the slave cylinders (prior to around '63) and part of the master cylinder after that point (talking stock GM parts). They should not have to be added either. Just convert our '62 Chevy truck from single to dual master using a '85 master cylinder back in March. I added nothing but extra line necessary to split the circuits.
Switched ports ( rear chamber to rear brakes,etc,,,) and it STOPAS !! Don't know why but it does ...thanks for all the suggestions boys... jersey Skip
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