Cascade Crew

Leejo2005 · Member Joined: 12 Jul 2009 Posts: 466 Location: Kennewick

So I finally have the new rear in the Firebird and have the brakes bled and sealed. I took it for a short drive to set the prop valve and I found that under no circumstance was I able to lock either the front or rear tires from 30mph. I have stock disks all around so I'm hoping that this is because my tires have too much grip for the stock brakes. Any thoughts?

It still stops pretty quick, but I thought stomping the pedal would at least get it to lock a bit.

Dewey316 · Posted: Sun Oct 09, 2011 6:39 pm Post subject:

stomp harder... or new pads, you should be able to lock 'em up with stockers once, the problem with the stock stuff is it overheats easier than the big brakes.

aaron_sK · Posted: Sun Oct 09, 2011 7:06 pm Post subject:

Mushy rubber lines, master leaking internally, booster bleeding pressure. Could be a lot of things.

Leejo2005 · Member Joined: 12 Jul 2009 Posts: 466 Location: Kennewick

I installed a rebuilt master cylinder for a 1988 with 4 wheel disks when I did this swap. It seems to be fine and the pedal feels normal. I had been able to lock the fronts at least when I had rear drums.

aaron_sK · Posted: Mon Oct 10, 2011 12:52 pm Post subject:

You did replace the prop valve when you did the swap?

Alphius · Posted: Mon Oct 10, 2011 1:16 pm Post subject:

Leejo2005 · Member Joined: 12 Jul 2009 Posts: 466 Location: Kennewick

I installed a wilwood adjustable prop valve. I was able to get the fronts to lock up this morning. Apparently the J65(4 disk) master cylinder has larger bore pistons. This makes for shorter pedal travel and higher pedal effort. I'm used to the J50(drum) master cylinder so I guess I just had to stomp harder.

Alphius · Posted: Mon Oct 10, 2011 1:32 pm Post subject:

Do you have verification for that master cylinder statement? I thought all thirdgens had the same master cylinder regardless of drum/disk rear? It was my understanding that the only difference was the prop valve.

You want to adjust your prop valve so that your fronts lock a little bit before your rears, but you do want to be able to lock all 4. Smile

Leejo2005 · Member Joined: 12 Jul 2009 Posts: 466 Location: Kennewick

http://www.thirdgen.org/techboard/suspension-chassis/58295-master-cylinder-differences.html

The brakes feel fine and balanced now just takes more force on the pedal than before.

I did find out that LS1 rotors and C5/C6 calipers will clear my wheels Smile

Alphius · Posted: Mon Oct 10, 2011 2:43 pm Post subject:

Interesting. Good to know. So if I want less pedal travel on my Z06/LS1 setup (with much more caliper volume than stock!) I can switch to the J65 master cylinder. Cool.

DBL_TKE · Posted: Mon Oct 10, 2011 2:58 pm Post subject:

What if you want less pedal effort AND less pedal travel? SOL?

chevymad · Posted: Mon Oct 10, 2011 4:44 pm Post subject:

Leejo2005 · Member Joined: 12 Jul 2009 Posts: 466 Location: Kennewick

Got the LS1 rears bolted on the 9 bolt today. I haven't hooked up the lines yet I still need banjo bolt washers. I ordered some brass rods today so I can weld up around the bolt holes and fill in the old bolt holes. I also had to have spacers made to make up the thickness of the back plate and keep the axle retained properly. All things considered I think it will be worth it.