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Old 09-18-2010, 04:05 PM
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Weak Line Pressure on Rear Drums

I have a '49 Merc Sled with a 327-Turbo 350. It has a Nova Sub and a 68-69 Camaro Rear. I have a 7" Power Booster with a Corvette Style Master Cylinder and a Combination Valve (all new). I'm running 2# residual on the front and 10# residual on the rear as the M/C is under the floor below the calipers. The M/C is shallow bore with the matching booster with proper measurement between booster and M/C.

I have great front Disc Brakes but very weak pressure to the rear drums. Everything is new on the rear including brake rubber hoses front and rear. I'm pulling 15-16# vac at 800 rpm.

Residuals are installed correctly with the out pointing to the rear and MC pointing to the Master Cylinder.

Rear wheels can't be turned when on jack stands when you apply pedal. Release and spin freely. The shoes are adjusted properly.

Hit the brakes hard on a dirt road and front wheels slide....rear wheels don't. Appears to be not enough pressure getting to the rear.

All advice and suggestions appreciated. Thank you~~~~Ron

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Last edited by Sweet-34; 09-18-2010 at 04:08 PM. Reason: add message
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Old 09-24-2010, 07:06 PM
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try replacing the hydraulic Y box in the rear, it should have a main brake fluid line running to it and then Y's to send fluid to both sides. it should be up above the axle by the differential cover. do the rear brakes squeak? if not then there is fluid going to them, but not enough to activate the brakes. try changing the splitter i have replaced them in my trucks a couple of times they usually run about $20. good luck!
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Old 09-24-2010, 07:21 PM
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Quote:
Originally Posted by 66elcamino
try replacing the hydraulic Y box in the rear, it should have a main brake fluid line running to it and then Y's to send fluid to both sides. it should be up above the axle by the differential cover. do the rear brakes squeak? if not then there is fluid going to them, but not enough to activate the brakes. try changing the splitter i have replaced them in my trucks a couple of times they usually run about $20. good luck!
It's all new....including rubber line and splitter. I think I gaining on it..........Low vacuum........bring the rpms up to 1200 or more and brakes work and vac is about 20. Looking for source of vac leak!!!!

Thanks for your reply~~Ron
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