Dual Master Cylinder - bore depth

[arbakken]

My 65 C20 had drum/drum manual brakes with the single pot master, so figured I"d swap for a dual and bought a 67 C20 master with a 1 1/8" bore. I bought a 7" dual booster off ebay so I could keep the air cleaner on my 230 I6. It took over a month to get the booster (don't ask) so I got bored and ran the lines and installed the master cylinder. Booster finally showed up, and I learned that there are both shallow and deep bore master cylinders. Mine is deep, but the booster is meant for a shallow.

I see there are spacer plugs that are expensive and take a long time to get here, and since my master requires a wrench to pop the cap on, I'd sorta just like to replace the whole master if I can get one from oreillys for $30. What master do I need? Running a 1 1/8 master without a booster isn't ideal...

Thanks!

[The Rocknrod]

I think this will answer your question - http://67-72chevytrucks.com/vboard/s...d.php?t=627904

[arbakken]

I already have that master cylinder (with the deep bore), but the intermediate pushrod is not the right length. I need a drum-drum 1 1/8 master cylinder with a shallow bore, but don't know what "application" to look for.

Or if someone has a deep to shallow spacer they'd be willing to sell me cheap...

[jocko]

Recommend go to local parts store (so you can confirm visually before paying) - ask for a 67-70 C20 Power Brake mc. You still may not get what you want, some of the minor deltas in power vs manual mc part numbers seem to have somewhat faded over the years and some folks have problems finding what they need. But the key is to search in the window after the dual pot was mandated and before disks came out - and specifically for a 3/4 ton WITH power brakes from the factory. Let us know what you find and good luck!

[MT65]

Originally Posted by arbakken

I already have that master cylinder (with the deep bore), but the intermediate pushrod is not the right length. I need a drum-drum 1 1/8 master cylinder with a shallow bore, but don't know what "application" to look for.

Or if someone has a deep to shallow spacer they'd be willing to sell me cheap...

When you have the m/cylinder with the bore that’s necessary for what you want, but do not have the correct intermediate link…just make it…the deep bore is for manual brakes from the factory, easy to work with. Most of these pins are 3/8 sae( fine) thread, select a bolt that’s too long, grade 5 or 8 will do, determine the lenght you need, you will have adjustment in the yoke, cutit, chuck it up in your drill press (if you don’t have a lathe), using a sander you can make any radius ball on the cut end that is necessary….this pin is under compression, not sheer or stretch so these grade bolts are more than sufficient….I have done this many times, no running around tryng to find the “combination “……

[arbakken]

I didn't try really hard because I didn't want to break my brake booster, but I couldn't get the intermediate rod out. Is there a trick to it?

[MT65]

Originally Posted by arbakken

I didn't try really hard because I didn't want to break my brake booster, but I couldn't get the intermediate rod out. Is there a trick to it?

The booster will have a pin out the master cylinder side that is not removable, (some) are adjustable to get your correct tolerance with the piston in the master, I use .015 for that dimension, they are sometimes difficult to adjust, Master Power Brakes sells a tool that is the best for making this adjustment, this is where the shallow piston master(power) and deep piston (manual) comes into play…just remember that lives are at stake if this is not done correctly…….