This is a disc/drum question so I hope I am ok posting here... my 72 Camaro has Disc on the front and drum on the back.
I am in the process of installing new drilled and slotted rotors, D52 Wilwood calipers and this master cylinder
http://www.summitracing.com/parts/wil-260-8556p
I have this propotioning valve.
http://www.summitracing.com/parts/rsd-pv71
Wilwood is telling me i need one of these
http://www.summitracing.com/parts/wil-260-3279
Does that sound right?? I thought the prop valve i had did what the residual valve there are telling me i need woul do??
Advise needed please...
RobNoLimit
08-02-2014, 09:13 AM
The first item, the master cyl, is a standard straight bore master. No problem. This will be on the firewall, (mounted above the calipers, so that gravity is on your side) so as far as residual pressure is concerned, you don't need to worry about the front (although many times I would add a 2lb valve in this situation to quicken up the response just a bit). But, you DO need to add in some residual line pressure in the rear. This is done to keep the shoes very close to the drum, so that the return springs don't collapse the wheel cyl. Without the residual check valve in the rear, when you lift off of the brake pedal, the return springs would continue to push in on the wheel cyl, and push fluid back into the master. Next time you hit the brakes, you first have to fill the wheel cyl, and move the shoes out to the drum before any braking starts. The second Item #PV-71 is not really a proptioning valve. It is a Metering Block. Almost the same, but not quite. Metering blocks are non-adjustable valve sets, all in one. For a disk/drum firewall mounted car, this should have no residual valve in the front section, and 8lb. to 12lb. in the rear section. Also, the block is machined to balance the front/rear braking bias. The bias machining takes into consideration weight, weight balance, wheel base, CG, available brake clamping force ft/rr, tire size...... Since your car is pretty close to the OE, a disc/drum Camaro metering block should be OK. Remember that the metering block (also called a combination valve) is doing three things. Front residual, rear residual, and brake bias. If you were to do a custom full aftermarket set up, you would address each of these three separately. This is where items like the Wilwood 10lb. check valve come into play. You would really need three valves, if not using the metering block. 1. Front residual (in you case, none, or a 2lb.) 2. Rear residual (in your case 10lb.) 3. An adjustable proportioning valve in the rear line to balance the front/rear bias. The simple way here is to use the Wilwood master and the Metering block for a disc/drum Camaro as this will most likely connect to the majority of the existing plumbing. Hope this helps.
Great information..just to be sure, you are saying if I use the metering block I have now there is no need to add the residual valve?
I have this proportioning valve and would like to use it.
http://www.summitracing.com/parts/wil-260-11179
I realize I would then use the residual valve, which i have no issue with
http://www.summitracing.com/parts/wil-260-3279
The problem I have is the brake lines coming from the back of the car has a 9/16-18 inverted flare fitting, I don't know if they make an adaptor to get that down to 3/16 which is what I would need to run into the valve.
Anyone know if such a fitting is available??