Brake questions

[Jules]

Hey every body, havent posted here in a while and now that google cant answer my questions I figured I would ask them here.

I did a front disk brake conversion on my 68 chevy but I didnt get a proportioning valve with the truck that I got the front clip out of. So after doing some reading I found out that I cant use my stock 4 drum valve with the disk brakes on the front.

I went to the local race shop and bought a rear adjustable proportioning valve and am just going to do my own plumming on the truck. The only valve that I need to get is a hold off valve but I cant seem to find one anywhere but thats not the issue right now.

So here is my question. The adjustable rear proportioning valve takes 1/8" lines, is it ok to run the entire rear brake system with 1/8" lines? From factory they had 3/16" line running to the rear brake hose then it split up with 1/8" lines to the wheel cylenders.

For the front system I am just going to run the 3\16 lines. I know it would make things alot easyer if I just had a proper proportioning valve but I have been to all the wreckers and every truck I find has 4 wheel drums.

Thanks for your time every one.

Julius

[dragonwrecker]

not sure about the line size.but as for the proportioning valve.if you are doing drum rear disk front i would think the 73 to 87 valve would work.if someone knows for sure either way please chime in.

[Jules]

You know, I was thinking about that for a while now and its been a while since I have been to the wreckers. I remember looking at the newer ones but for some reason I think they were using 1/4" lines on part of it and I think I recall there being something els on there that I didnt need. But if I need to I might have to make it work. You would think that there would be more of the 71-72's at the wreckers but around here it seems like they are all pre 1971. I dont know if I can get away with just running the rear of the master to a "T" to go to the front calipers and just running my rear through the adjustable prop valve. As far as I know the only other things in the factory prop valve are a hold off valve and the brake switch.

[treveiger]

Interested
Posted via Mobile Device

[Jules]

Can't believe more people haven't chimed in yet. I found a used valve for my truck but the guy wants 100 for it...
Posted via Mobile Device

[slikside]

You can buy a new prop valve from Summit or POL. I think POL may be a few bucks cheaper, but at most about $62 I think.....but you live in Canada, so it could be a bit more for you with shipping, etc.

I may have to go this route as well.

Good luck..

[70cst]

Hey Jules ,,,

to the forum and from Ohio

[Jules]

Hey man thanks for the welcome!

I found a prop valve today I just have to go take it off the truck how are these trucks for even braking? Do the back brakes ever tend to lock before the front? Last time I drive my truck (10 years ago) it was drums on all 4 corners. I ripped the entire truck appart with the intention of restoring it and wala! We had a kid! so that slowed everything down till just recently. I sold the small block I had in it at the time and built a 383 stroker short block all I needed was heads and guess what happened... Another kid! Lol so I sold the 383 and put the truck on the back burner.

Last summer I traded a guy some (1200) hotwheels for 2 more trucks and a done up 250il 6 so that's what I have in it now. It actually sounds pretty strange with open headers and a nice cam. I was going to go the small block rout again but after finding this 6banger with 3000 miles and a whole lotta performance parts I decided to be different and go for it.
Posted via Mobile Device

[Jules]

The info in my first post was wrong. After some more research I found out the rest brake lines are 1/4" and 3/16"

I bought a prop valve today and it came with the master, booster and all the brackets and linkages too
Posted via Mobile Device

[airdale94]

The 1/4" lines are for the rears, and the 3/16" lines are for front disc. The reason for this is for the front disc you need more pressure. The rear wheel cyls. need more volume(of fluid). If you Google brake line sizes you will get a better description of why it is this way.

Ah physics!

Now on your master cylinder the larger resevoir is for the front discs.

[Jules]

Thats what I ended up going with for line sizes. Thanks for all the help everyone. Both of the resevoirs on my master are the same size but I double checked it and it is a power front disk rear drum master...

So I spent most of the day with my 7 year old son at the shop working on my truck and hardly got anywhere. First off I cant use my brand new power brake setup with the six banger and four barrel carb... the booster hits the carb and doesn't leave any room for the air cleaner. Just to get me by I mounted the power brake master to use as manual untill I can get another master. I mounted the prop valve and went down to the part store to get some lines to replace the ones from the master to the prop. Why do they have to have three different fitting sizes just for those 2 lines???

I have seen a few different setups done on these things on the internet so I just did what I though was right. The metering valve is on the front of the prop valve (closest to the grill of the truck) so I ran the rear port of the master to the front port of the prop valve and ran the front port of the master to the rear of the prop valve. I read that the rear port of the master is for the front brakes and the front is for the rear. I have also seen it run the other way around... so whats up with that? I just cant wait till this thing is done... way to many issues just running new brakes its unreal.. I think that the prop valve I have is faulty because it lets fluid flow freely through the front circuit and the rear circuit... it seems like the metering valve isn't working the way it should be.