master cylinder interchangability?

[bitchin85]

my 85 half ton 2wd 350/350 has/had a master cylinder with the plastic resivuor. i went to buy a new one today and they only had ones that are full metal with the metal cap and all. so i got one. will it fit right? will it bolt right to my brake booster and are the lines the same size? and wil i feel a difference driving it? id imagine this is a heavier duty one? thanks guys

[bitchin85]

Anyone?

[ToughBowtieTruck]

The only difference you may have is the reservoir sizes compared to the old tanks. The older cast tanks I think either had equal size tanks or a small one for the rear brakes. I don't think the cast bodies let the tanks "share" fluid either (plastic one lets a tank running low draw some fluid from the other until a certain point).

I don't see you having a problem, just measure the depth between the bolt flange and the plunger end to make sure they are the same distance so the brakes will apply/release at the same times.

It's not really any more heavy duty, they are only as good as the rubber seals installed, more of an older style that was used on the 70's trucks before plastics and aluminum came into play.

[bitchin85]

Your right about the resivuors. So the all cast one is just older? Ok I hope it bolts up to my brake booster

[ToughBowtieTruck]

Originally Posted by *****in85

Your right about the resivuors. So the all cast one is just older? Ok I hope it bolts up to my brake booster

Should fit. Just check to make sure they look the same where it bolts to and fits in the booster.

[Keith Seymore]

Here's all the different ways there are for a master cylinder to "not fit":


Bore Diameter
Quick take up vs non quick take up
Flare type (iso vs us)
Flare location (inboard vs outboard)
Reservoir location (ie, front location feeds front system, vs front location feeds rear system)*
Reservoir size

Having said all that, if it bolts up to the booster, and if the correct portion of the reservoir feeds the right system, then you should at least have functioning brakes.

K

*I believe on some old cast iron systems the front res feeds the front axle and the rear feeds the rear; whereas on the plastic/aluminum masters the front feeds the rear and the rear feeds the front. You can tell by the reservoir size (small feeds rear; large feeds front). I'd check that first thing.