Hey guys,
I have a 70 Monte with power disc/drums. I would like to switch to a manual setup and eliminate the power brake system.

From my understanding a good master cylinder would be 68-76 Corvette with a 1 inch bore. I would like a 1 1/8 just for the extra line pressure but not too sure if it is worth the extra work in terms of drilling out another pedal hole. Plus I believe the 1 1/8 is meant for a power disc setup.. This master would have the deep pushrod hole which would like require this kit..

http://www.opgi.com/product.asp?topcatid=6&chapterid=6&topvalue=0&newflag=0&grpcode=13219&yearrange=

Would these be good part #'s for the master?

DORMAN M89160
A-1 Cardone 101423
Cardone Select 131423
Raybestos MC39018
AC Delco 18M72

or 101371 Master Cyl. that is Cardone brand with a deep hole and 1" bore


If I go the manual route will I have to change the pedal pivot hole to the higher hole?

thanks

The 1 1/8 bore will give you less pressure-It will give you more volume for the same stroke though you'll only need that with very large caliper piston area(rare on pass cars)
I run the 1 corvette master cyl. on the Heap-great pedal feel and not grandma unfriendly(or ford knee)-70 camero(12 in rotor)calipers in the front and Caddy Crip De ville calipers on the back(10.5in rotor)
Yes on the higher hole(oh I could get dirty on that one:D)

I used the 101371 and needed a 6" rod to use with the original clevis. You would need to use the upper hole and remove the existing tab for yoour brake light switch. Very simple conversion.

A manual disc master cylinder from a 68 chevy truck was only $14 with trade in from Advance Auto parts for my 70 Monte. It fits great but I have not had it on the road yet.

I used the master cylinder off a 68 Camaro for manual Disc brakes. I beleive it has a 1 1/8 bore. Big improvement. Can get a rod for manuel or make one as someone said 6 in. long.

Hey thanks guys,
creeper it's cool you are in the process of doing this. It is a great information source.

YellowHeap, if I changed the stroke will it utilize the 1 1/8 bore better?? I recall reading DoorSlammers and he had a section on the proper ratio. It would involve measuring the pivot points etc. I guess though this would involve drilling new holes instead of just using existing ones?? The 1inch bore seems to be a easier install.

I heard it can be a big tricky finding out proper rod length due to a mix mash of rod sizes?? You could always use some 3/8 threaded rod to do the trick..

I have talked to atleast 2 guys here that used the 1-1/8 and were happy. I wanted the 1 " bore based on wildwood's suggestion of a 7/8 bore from them.
I think the only difference you are going to see between bore sizes is the "feel" & travel of the pedal.
I like the 1" bore, but may have been just as happy with the 1 1/8. A small amount of people using the 1-1/8 complained about pedal travel and a spongy pedal?????

I dont think drilling any new holes would be worth the effort. JMO

I heard it can be a big tricky finding out proper rod length due to a mix mash of rod sizes?? You could always use some 3/8 threaded rod to do the trick..

I'd recommend against using threaded rod -- the material used for allthread is typically pretty weak stuff. Better bet to get a long grade 8 bolt and cut the head off --- better material strength and less likely to bend/brake. Takes a little more work to cut the head and round off the edges, but in my opinion worth the extra insurance.

You could drill a new hole slightly up from the normal Manual brake hole for more leverage against the master cyl. but why bother-get a 1 1/8 if you don't like it get a 1 in and so on-or just trust Chevy and run a 1 in.:D
I don't think you'll be disapointed with the 1 in.
My brakes are REALLY nice for a bunch of junk yard crap(Quality GM crap)
pedal feel is sweet and with a moderate effort it really brings THE HEAP to a halt.

Hey guys,
I ordered the 101371 from CarQuest and I am picking it up tonite. If it was the winter and I had more time, I might try to get the 1 1/8 bore going but the 1 inch hole is already there.

Creeper, Where can I get a 6 inch push rod?? I will talk to CarQuest tonite..

I have a low vac condition and it makes it hard to stage the car when bracket racing. Hopefully, I will "bump in" better now!

Monte, I had to make my own pushrod. The stock clevis is 3/8 fine thread..... so it can be a pain.
If you dont care about your old booster- cut enough rod out of it and just grind the end.
There are some brake companies out there that make them for about $25.

A fastener shop should be able to order a 6" fine thread bolt for you and just grind the head off , or use coarse thread and drill out your clevis.

If you want to just buy one.... Here is one of the best deals.

http://www.resto-modtechnology.com/servlet/the-206/MANUAL-BRAKE-PUSH-ROD/Detail

Thanks again Creeper,
I will pick up some 3/8 fine 6 inch long at the fastner shop tonite. Once I get taking everything apart I will have a better idea of what is going on. Right now I am only referencing diagrams. It is excellent having all the help and therefore knowing what is needed to be done beforehand (ie getting a 3/8 fine 6inch bolt)
I don't want to disable the car for racing Sunday so one more time staging with inconsistent pedal. I am planning to start on it Sunday night hopefully.
Kris

I had a hard time finding it in a grade 8 in stock , but it could be ordered. You may get away with a lower grade.
As said... Do Not use threaded rod.

Yes I am lucky I guess. The fastner shop has 150 gr8 F/T 3/8 6 inch in stock. Not too many fastner shops around here sell bolts individually anymore, it seems like it isn't profitable..

Hey Fellas,
I finished installing the manual unit awhile ago but I haven't had a chance to post up results...

2 things I learned;

Make sure that the front pads don't drag before test driving it. Put the front end up on jackstands and spin the front wheel by hand it should turn somewhat. I didn't do this and about 10 mins into my rest drive the fron pads were smoking!! I had to reducing the threads on the pushrod to stop this.

The brake light switch doesn't like the full release of the brake pedal engery on it. It will loosen off and produce a full time brake light situation. I had to reduce the length of the white plastic nipple that contacts the pedal to stop this happening.

Here are some pics,

Had to bring this back. You never told us how you like the feel. How hard is it to stop compaired to the power?

Had to bring this back. You never told us how you like the feel. How hard is it to stop compaired to the power?

Ditto.. bump.

Good thread as I am in the middle of this conversion myself. Having a heck of time finding 6x3/8 fine thread bolt though! Might just have to cut out the rod from the old booster, but rather not. I'm using the original (new) master cylinder for a 69 Chevelle SS, I was told it would work fine without the power booster. I believe it's a 1-1/8 bore, can anyone confirm?

I just put all new Manual Disc/Drum brakes on my 72 Monte.

I put on Earls hyper-firm flex lines & SS lines from Inline Tube.

Master Power Brakes 1" master cylinder MC1702K (made for manual disc/drum + adjustable rod)

Fronts are 11" Summit disc & SSBC dual 38mm piston calipers.

Rears are Master Power Brakes big drum kit DR1700K, 11"x2" & 15/16" wheel cylinders.

I reused my original Combination valve, as it looked fine & don't leak.

A buddy & I just finished bleeding it, used 2 quarts of new Dot 3

I'm happy with how the pedal feels, high & not mushy.

It's still up on blocks so no road testing yet.

Hope it stops well

BBP

I just put all new Manual Disc/Drum brakes on my 72 Monte.

I put on Earls hyper-firm flex lines & SS lines from Inline Tube.

Master Power Brakes 1" master cylinder MC1702K (made for manual disc/drum + adjustable rod)

Fronts are 11" Summit disc & SSBC dual 38mm piston calipers.

Rears are Master Power Brakes big drum kit DR1700K, 11"x2" & 15/16" wheel cylinders.

I reused my original Combination valve, as it looked fine & don't leak.

A buddy & I just finished bleeding it, used 2 quarts of new Dot 3

I'm happy with how the pedal feels, high & not mushy.

It's still up on blocks so no road testing yet.

Hope it stops well

BBP

Let us know... My setup I have planned is a little different. I have a 15/16 bore master , Single big piston caliper, Halk HPS pads, SS flex lines and stock drum rears. I didn't do my swap yet. I'm hoping it will be good.

Hey guys,
It is certainly a different pedal feel, you have to exert more leg muscle to stop (but not like the leg press machine at a gym were you would single leg press 800 lbs). I normally leave a lot of stopping distance on the street anyways. It seemd a bit easier to apply the line lock and "catch the pressure" of the front brakes. The bore of the master is 1 inch.

I didn't notice a huge difference for staging but then again my staging technique got better as the year progressed...


I have heard the fine thread bolt is hard to find..
I think the real value of this conversion will come when I switch to a more powerful camshaft with a very low vacuum output.

Kris

I am also in the middle of the single master 4 wheel drum to front disc dual master manual converson with a Ground Up kit.

The pedal pushrod was too long for the new master, until I realized the new master had a spacer in it. Removed the spacer, it fit fine, but its not done and I have not driven it.

In the midst of this, I called Ground Up, who put me on Right Stuff, who sells a new pushrod and clevis with the right threads, etc. Got one of those, only $14 delivered. That may be another option.