are my front/rear brake lines crossed?

[drdata]

A silly question but my manuals are not clear. On the 78 I just sold it was clear that the MC had a larger front compartment and corresponding brake line. Makes sense as I understand disks need more fluid than drums, hence bigger reservoir and line diameter.

On my new to me 72, which has dodgy brakes, I note that:

1. The MC seems to have the same size reservoir. Is that correct for a front disk/rear drum 72 blazer? It seems to match that shown in the link below.

2. The larger line from the rear MC port goes to the rear drums. The smaller from the front hits a slitter and goes to the front disks. This seems backward, but given the different thread sizes for the two lines it seems unlikely this could happen by accident.

This link has a decent diagram, but has a nice "air gap" such that I cannot use it to confirm which port on the MC/proportioning valve goes to which set of brakes:

http://www.lmctruck.com/icatalog/cb/full.aspx?Page=151

In my case the rear line is larger, and again goes to the back brakes which are drum. The front thinner line feeds the front disks. Is that correct?

Thanks in advance.

[drdata]

Bumping for some blazer love! C'mon guys.

Perhaps I need to ask in a more direct way.

Can someone with a known to be stock 72 blazer that has disks/drums confirm which brake line feeds their front vs. the rear?

Are your front disks attached to the thicker or thinner of the two lines?

Thanks

[1949gmc]

Here's a picture of my truck. Disc/drum vehicles always have a mc with a large bowl in front for the discs and a small bowl in rear for the drums. If you have a 50/50 mc, then somebody put the wrong one on. In my pic, you can see that the big line that you're talking about is definitely for the rears while the smaller line is for the fronts. I may have a little bit better pic somewhere if this one doesn't help.

[drdata]

Originally Posted by 1949gmc

Here's a picture of my truck. Disc/drum vehicles always have a mc with a large bowl in front for the discs and a small bowl in rear for the drums. If you have a 50/50 mc, then somebody put the wrong one on. In my pic, you can see that the big line that you're talking about is definitely for the rears while the smaller line is for the fronts. I may have a little bit better pic somewhere if this one doesn't help.

Attachment 513358

Thanks for the reply and confirm. At least it seems the brake line routing is correct. On the MC front, I agree that most have larger front than rear, but when I look for 1972 chevy blazer replacements they all seem like mine, which is to say equal sized front and rear. See these links:

http://www.brotherstrucks.com/prodin...number=KORN772

http://www.car-stuff.com/store/?N=98...588+11921+9182

So now my question becomes what is the correct MC for a 72 4wd blazer? Is it symmetric or asymmetric?

Thanks again.

[1949gmc]

I still don't think that the 50/50 mc is correct, unless your truck has drum/drum or disc/disc... holds true for any vehicle. For disc/drum, you'd have to use the 70/30 mc. Now, did Blazers come with drum brakes on the front in '72? If they did, did yours have drums that someone converted to disc w/o changing the mc? Or did someone absent-mindedly just put the wrong mc on?

[lks dcvn]

71 and 72 front disk brakes were standard on chevy and GMC trucks and blazers - my guess is wrong MC installed if you have front disk brakes.

The PO of my 72 4x4 Blazer redid the brakes to drive it up from Columbus - he put in a new booster and the wrong MC (drum/drum) - It will stop, but not that well.

Not sure how he drove it 200 miles on the highway like that, but he did

He said that it is an old truck and the brakes don't work like the cars of today - err - yeah - that is wrong. It is on my 'to do' list.

[Burt4x4]

Here I found it:
http://67-72chevytrucks.com/vboard/s...highlight=1Ton

[drdata]

Burt, thanks for posting the link.

I should have the correct bracket. If so does sound an easy swap.

Will keep the thread posted.

Regards