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Disc brake swap brain fart
https://slantsix.org/forum/viewtopic.php?t=44469		 Page 1 of 1
Author:  Reed [ Mon Apr 11, 2011 4:25 pm ]
Post subject:  Disc brake swap brain fart
OK- it has been awhile since I did a disc brake swap on an A-body. I am in the middle of swapping the front brakes on my brother's 74 duster from the factory ten inch drums to discs (I started this project two years ago and got it to the point where it can rest on the front wheels, but didn't finish installing all the brake parts).

When swapping from ten inch front drums to disc brakes in a 74 Duster do i need to switch the proportioning valve or can I just keep the stock metering block? I also upgraded thew rear axle to 11 inch drums. Will that affect my choice of metering block?

I used to know this stuff but I have forgotten.

Thanks.
Author:  emsvitil [ Mon Apr 11, 2011 4:45 pm ]
Post subject: 
Keep the original drum brake metering block and use an adjustable proportioning valve for the rear drums. (added after the metering block)
Author:  Reed [ Mon Apr 11, 2011 4:50 pm ]
Post subject: 
OK, thanks!

I suppose I should route the new adjustable prop valve inside the car to make fine tuning it easier.
Author:  Andy's GT [ Mon Apr 11, 2011 8:50 pm ]
Post subject: 
im at the same point after my dart sitting pretty much for two years. having a time getting the fitting off the metering block, good luck with finishing yours up!
Author:  Joshie225 [ Mon Apr 11, 2011 9:30 pm ]
Post subject: 
Quote:
OK, thanks!

I suppose I should route the new adjustable prop valve inside the car to make fine tuning it easier.
Unless it's a race car you're trying to adjust for optimum threshold braking with changing fuel loads it's much easier to put the proportioning valve near the master cylinder. I did it this way for the Barracuda. If I later decide to road race the car I might move the valve to the floor to the left of the driver's seat.

Image
Author:  Reed [ Mon Apr 11, 2011 9:44 pm ]
Post subject: 
Thanks Josh! I know you know your stuff when it comes to A-body handling.
Author:  kesteb [ Mon Apr 11, 2011 10:36 pm ]
Post subject: 
Put the correct proportioning valve in the car, use the correct wheel cylinders in the rear drums, use the correct rear drum setup, and use the correct master cylinder. This should give you a nicely balanced system that brakes straight and even.

The stock disk brake system from the factory was well designed and I haven't experienced a better system until the late model 4 wheel disk brake systems with ABS in my Nissan's.

I would consider an adjustable proportioning valve a crutch for a badly assembled factory system, especially since the factory did such a good job.
Author:  Joshie225 [ Mon Apr 11, 2011 10:59 pm ]
Post subject: 
You have a higher opinion of the factory disc brakes than most. My wife's old '72 Duster with KH disc brakes suffered premature lockup. My '74 Duster with disc brakes suffered premature rear lockup. The factory did not do a good job with either car.

Adding a proportioning valve to a car that didn't have one by virtue of originally being equipped with 4-wheel drum brakes is perfectly prudent. Having the valve adjustable and adjusted correctly will improve the braking over most any factory installation.
Author:  Andy's GT [ Tue Apr 12, 2011 1:02 pm ]
Post subject: 
My instructions from ssbc say to put the valve after the metering block (67 dart, originally 9" drums all around), cant get line loose and was thinking that putting it by the mc would be a lot easier and a better install due to limited space near the metering block. Sorry to hijack the post, just at the same point and this could make my job be done sooner. Thanks!
Author:  emsvitil [ Tue Apr 12, 2011 2:16 pm ]
Post subject: 
If the metering block has the electrical wire on it to sense if you've lost half of your braking system, putting the proportioning valve in front of the metering block may trip the brake light because pressures aren't equal on both sides (F/R).
Author:  Andy's GT [ Wed Apr 13, 2011 9:32 pm ]
Post subject: 
thanks!
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