I need a master cylinder reccomendation!

[carguy502]

OK, fellas.

I want you all to chime in on a solid MC reccomendation for my 1969 Nova. I have done research, but I have to admit that I am a little confused as to the correct course of action. Feel free to lay some knowledge on me.

Car: 85% Street/15% Track 1969 Nova, Approx 3260 pounds with a full tank (~15 gal)
Front: Wilwood D52 2" twin piston front calipers with 11 inch rotors
Rear: Currently the late 70s Trans Am rear disc brakes with parking brake
Soon to be Willwood rear floating caliper kit with D154 1.12" twin piston rear calipers and in-rotor parking brake
Prop Valve: Wilwood Adjustable
M/C: Currently a SSBC Vacuum booster and a heavy as all get out Iron M/C from a 1979 Trans Am 1 3/16 bore measturd at opening (could be 1 1/8)

Goals: I want a light alternative to the iron OE M/C that has similar braking capabilities, but I don't want to break the bank with a spanking new Willwood MC. I also like the OE look so, if possible, late model M/Cs are OK if they are bolt-ons or close.

Thoughts?

Thanks in advance,

Don

[Skip Fix]

The 4WD TA MCs are 1 1/8" as were the disc/drums those years. The 4WD used a smaller dual diaphragm booster that works quite well with little vacuum. The 81 TAs used an aluminum quick take up MC but the register was larger than the iron earlier ones so it used a different booster. I think all the GM MCs used the same bolt spacing just that register changed sizes. Not sure the size on the SSBC. Might need to measure that before you buy another MC.

[Apogee]

How much vacuum at idle? What size SSBC booster? Single or dual diaphragm? What pads if not the semi-default Wilwood BP-10's?

The only down side that I see is that Wilwood has not yet made a D154 caliper variant with an effective piston area anywhere near 3 square inches, only 1.98, 4.12 and 4.90 square inches. Given the front D52 caliper piston area of 6.28 square inches, if you were trying to match the original bias of the 79-81 T/A, then a 3.1 sq. inch option would be ideal, so it might be worth a call to them to see if they're going to offer anything in between their current D154's in terms of piston area.

Once you figure out your caliper piston areas, then you can look at what you want to do with respect to the master cylinder. Pad choice and all of the questions I asked above should be taken into consideration as well.

Tobin
KORE3

[carguy502]

It's 19 inches of vacuum right now (stock L98 smog cam), but I am going to a slightly more aggressive camshaft (LT4 Hot Cam) that will bring it down a bit. Based on other peoples combinations, I should be seeing 15-17 inches of vacuum. It is going to a ssbc 9 inch single diaphram. Pads are yet to be determined, but will probably be Performance Friction semi metallic (HD street compound commonly available at your local auto parts store). Since Wilwood is unlikely to offer an in between piston size, which would be more advantageous, 1.98" or 4.12", given an adjustable perportioning valve?

Don

[Skip Fix]

My TA dual diaphragm booster has worked fine even with 9" at idle, but I would bet even the single boosters should work at 15".

You could always just use "metric" front calipers that are the original D154 that have about a 2.5" piston in the rear. Cast iron not as pretty. Wilwood does have a "metric" alumiunum caliper single piston but it does not have the outer O ring slides for the bolt so there is some flex possible there.