Brake booster/ MC question

[stexag]

I'm getting around to the things on my truck that function, but just bother me. This is one of them. I know that the master cylinder is definitely not right, and I don't think that the booster is either, but I have seen a picture or two on here of ones like it. I have a 73*87 front crossmember w/ discs, drum rears. I plan to upgrade the rear brakes next and do something about this monstrosity.

What should stay, what should go? What is best to replace it with? I'm pleading ignorance. Thanks.

[knomadd]

What kind of style are you looking for? If you just want to get rid of the plastic look, you can get a universal corvette style master like this one


Or something from Wilwood like this


The booster would be fine, as long as it works now. Replacements would be similar if you stay with a vacuum style booster.

Check out places like classic performance Wilwood Pirate Jack Summit Racing Jegs

[VA72C10]

If you just don't like the look, get one from CPP off ebay...or go to NAPA or any parts store and get a new or remanned factory style one...

[70C10Toejam]

I have '85 disks, steering and calipers in my '70 so I'll tell ya what I know. I don't know when the change was made, but GM switched to a low-drag caliper which resulted in a redesigned MC. That is when the changed to the aluminum ones like yours. The low drag calipers need a high volume low pressure initial part of piston travel from the MC.

The MC will not fit to a single-diaphragm booster that is original for your truck. The hole in the front of the booster is too small. It may fit into a dual-diaphragm booster, the hole is larger. I have not tried it yet.

If you want to change to year correct MC/booster, you should change your calipers too.

I had a link that explained this very well but it no longer exists. And I have no pics that would help.

[stexag]

toejam - Does that mean that the calipers available to change the rear brakes are incompatible with the later low drag calipers? Is there a way to tell which calipers are which by looking? If I understand what you are saying the switch could have been anywhere in the run and since I don't know what year my front end is (it could be a 73, or an 87) - I really don't know what calipers I have.

[70C10Toejam]

I would guess you have the 87 calipers, since that is what the crossmember came from. Do you have a metric/o-ring PS box too? Would make it more likely the calipers are 87. Don't know how to tell by looking at the calipers, a casting # should tell you. Don't know how to interpret that though. Might check for a rear disk conversion for 80-87 pickup, would have the same calipers.

Measure the thickness of your disks to find out if you have regular or HD brakes. 1 inch is regular and 1 1/4 is HD. The old standard was 1 1/4, but late 70's or early 80's GM decided to make this change.

[stexag]

I don't know about the metric/oring PS box. When I said 73 or 87, I meant 73,87, or anything in between. According to some research I did today GM adopted the Quick Take up MC somewhere in that run and yes, it's hard to differentiate between the calipers. This thread says parts can be mixed and matched, as long as the MC will fit the booster http://67-72chevytrucks.com/vboard/s...d.php?t=514972 but some other websites have indicated that mixing parts can make the petal mushy.

More scouring the interweb to make myself smarter about this....

[70C10Toejam]

Checked out that thread, and looks like they caught the basics pretty well. The biggest hurdle is that you don't really know how much of the donor truck was used. If you have the thinner rotor you would have the quick take up calipers. 1 1/4 could be either one. It might help if you have a self-serv scrap yard and take a look at trucks with these different MC's and see if you can find a casting number to compare yours with. I don't know that I have much else to offer on this.

The interwebs are a vast space

[67 chevelle]

id go hydroboost , they are great , that is if you have power steering

[knomadd]