C5/LS1 G-body Brake Conversion Questions

[86Cutlass383SR]

I posted this on another forum and I thought I'd ask here and see what you guys thought. I've read and read enough opinions to throughly confuse myself. Since I'm building a daily driven street car, this is obviously something I don't want to get wrong.

I'll be running the 13" Vette C5 front calipers and rotors with a bracket from Ed Miller on a stock g-body spindle. I may upgrade later to the S-10 ZQ8 (?) spindle but I don't think a differance in spindles will matter since I'll be using the same calipers and rotors.

The rear will be the 2000 Camaro LS-1 rear disc brakes with the e-brake hooked up.

Here's where my confusion begins. I also had Ed Miller modify a stock proportioning valve for my rear disc swap. Should I also run an adjustable valve in the rear line or leave it out?

I've read some guys recommend just running the front line to a "T" and then to each front caliper, and then doing the same to the rear with an adj valve in the rear only. I don't have a problem with this setup except I'd also like to have a brake warning light since this will be a street car.

If I understand correctly, I can use the stock master cylinder unmodified. I have no idea of the bore size. According to NapaOnline.com the new master for the 86 Cutlass is a stepped bore (24mm/36mm) and the remaned cylinder is listed at 24mm only.

I am getting ready to run all new brake lines. Do I need 3/16" or 1/4" brake line? (I think I've read 3/16" is best?) Any special adapter fittings required for this conversion? I got my front caliper/rotors from DiscBrakesRUs years ago and the setup included front braided lines. Okay to use these (still unused) or should I just run stock rubber lines? Vette or G-body?

Any other tips and/or hints in my swap would be very appreciated. I'd like to not have any surprises when I get this car on the road again.

Thanks

 

[jrm81bu]

Maybe I can help with a bit of that, but this is just my opinion. I would run the 3/16 line for the fronts and use 1/4 to run from the prop valve towards the rear, pretty sure that is the factory way.
As for the prop valve, I've read or heard that since you now have a disc/disc prop valve, just use it. Then if you have a problem with locking up the rears add an adjustable valve after the factory valve. The only problem I could see doing it that way is if right of the bat you're modified prop valve could have even more pressure going to the rears, and then it would only be a matter of not using the rears to their best ability.
On the spindles, you're talking about the s10 spindles that use a hub assembly right, and come with dual piston calipers? If so you're vette rotors should just slip on, but there is a good possibility that caliper bracket may not work.

 

[86Cutlass383SR]

Thanks for the quick reply.

I was kinda thinking along the same lines as you concerning the prop valve. Using the adj valve in the rear line to back off the press if needed. I've never used an adj valve but I thought if you could go from full press or completely open, to no press which would be completely closed, it would be okay to use in the rear line. Start with the adj completely open and adj down to where it no longer locks up.

I also believe you are correct on the line sizes. I was thinking about doing the 3/16" front and 1/4" rear lines.

Tobin at Kore3 makes a C5 bracket for the S10 spindles. Yeah, it is the ones with the sealed bearing I was referring to. Those are supposed to be better for the C5 swap as the g-body dust shield holes gets rather thin when drilled/tapped for the needed caliper bracket. The S10 ZQ8 bracket is differant than the G-body bracket.

 

[FE3X CLONE]

On my '87 I basically used the stock line sizes. 3/16" up front to each caliper from the proportioning valve. 1/4" from the proportioning valve to the rear distribution block at the rear end. Then 3/16" lines from that block to each rear caliper.

For my proportioning valve I bought an aftermarket brass valve and just gutted the inside of it. Then added a Jeg's adjustable proportioning valve in the 1/4" line heading to the rear. Not sure that will work with a brake warning light but my dash setup doesn't have a light for it so I wasn't concerned about it.

For a master cylinder I'm using a stock replacement for mine. I was told by more than one person that the stock G-body master cylinder is plenty for this setup.

 

[86Cutlass383SR]

Okay, I just saw on SummitRacing.com that apparently closed is only 57% instead of my assumed 100% closed. Ya know what they say about assuming... :shock:

 

[86Cutlass383SR]

Many thanks to both for the replies!

Andrew, if you would, please keep me posted on your setup and how it's working out or if something needs to be changed.

I think that's basically what Ed Miller did to my prop valve, just removed the rear press valve so now all it is is just a distribution block. I'll probably add in my adj valve and open it completely and reduce press as or if needed.

It may or may not work with the stock brake light. My concern is not so much for me, but if someone *other* than me drives this car, I want the brake warning light functional if possible. It will be a daily driver so I'd like as many safety warning systems working as possible.

 

[79loserbluebu]

I know it seems a little silly to add this but, for the spindles, they are just 2WD Blazer spindles, 98+. The ZQ8 referred to the suspension rather then brakes. 4WD spindles are different from the 2WD so if you go junkyard hunting avoid the 4WD ones. It may just be easier for you to locate some by searched Blazer. I know www.car-part.com asks what options it had like ZQ8 or ZQ3 but it won't matter for these.

Question for you guys, do S10 or Blazer spindles affect ride height?

 

[86Cutlass383SR]

Yeah I knew about the ZQ8 suspension. A lot of people just tend to think of the S10 spindle that is the same as the g-body spindle so I just wanted to differentiate between the two.

I've used the link you provided many times but I'm glad you included it for those who may not know. It is a valuable link. I have 4 U-Pull-It yards but they are about 100 miles away. I'll find a set somewhere I'm sure. Also, I think you can use the 4wd versions, they just have a hole in the center for the fwd shaft to come thru. They say it can be plugged but I'll just stick with the 2wd versions.

From what I've read, the ride height is not altered.

 

[79loserbluebu]

Okay yeah I didn't want to seem like a know-it-all but I was just saying incase someone didn't know and get shafted on someone selling a set of "ZQ8" spindles when they can find them from any Blazer.

That is definately some useful information about it not affecting ride height 8)

 

[86Cutlass383SR]

Not a problem at all. Sometimes we get caught up in an answer and tend to forget others are watching the replies for answers to their questions. On one hand we need to be very specific yet in doing so, not to insult others intelligence.

I took no offense and yeah, it was a good idea to clearify that. Thanks! :wink:

Remember, I said I don't *think* they lower the front. Since I'm going to go that route, too, I hope they don't at least.