C8 progress in Texas

David DeWeese · #1 15-02-09, 05:26

Started sorting out my non-existant brake system today. My original master cylinder was cracked,(no good even for a core), and all the metal brake lines needed replacing.
Because of this and as a concession to safety, I installed a dual reservoir master cylinder on the C8 today.
A trip to the scrapyard yielded a good choice as it had the brake line outlets exiting the right hand side and a very low filler cap profile. Came from a 1970 Jeep Commando. Very cheap for new ones at the local auto parts store.
Made up a heavy bracket and bolted it up. Re-installed the old 216 motor, installed floor plate and wood strip to check clearances. Not much room to spare, but it fits, it's safer and it's cheap!

Thanks, David

sth65pac · #2 16-02-09, 11:09

Great work David,

I am a firm believer that a dual circuit system is a safer bet. Jeeps of that era are not common here in Australia, but I am of the same mindset: Two circuits are better than one.

You are going to have to look at a servo to assist the braking as I do not think that the jeep system uses the large bore diameter like the C8 originally had.....SO (I think) your pedal pressure will be too high and you will need a right foot on steroids to push the pedal hard enough to work the brakes effectively. [One has a sneaking suspicion this thread will end up immortalized in Google] Perhaps you have re-bored the master cylinder to the larger diameter (I don't know) if so, the problem above vanishes...

Let us know how you go... we're happy to learn from your mistakes

.

You can hide a servo easily enough.

I have actually rebuilt my original master cylinder, but it will be to get me mobile. I want to convert to two circuits.

Ian

David DeWeese · #3 16-02-09, 16:00

Thanks Ian for the reply! Any and all input is gratefully appreciated as I am flying blind on this modification.
The only thing working for me is that the donor Jeep had non-power assisted brakes and 11" drum brakes all around. Didn't check wheel cylinder diameter though.
Add to the mix that the C8 has a late model rear end installed that had power-assisted 11" rear drum brakes, and the front brakes are from a much earlier General Motors product, (that way when I received the truck), I have a real brake salad going!

Thanks, David

Note;
It also has occurred to me that some people may be put off by taking these great liberties in modifying such a rare truck. My decisions are based on time, money and the mechanical condition of the truck when I received it. If I am offending anyone, please let me know.

Alex Blair (RIP) · #4 16-02-09, 16:44

Quote:

Originally Posted by David DeWeese

Thanks Ian for the reply! Any and all input is gratefully appreciated as I am flying blind on this modification.
The only thing working for me is that the donor Jeep had non-power assisted brakes and 11" drum brakes all around. Didn't check wheel cylinder diameter though.
Add to the mix that the C8 has a late model rear end installed that had power-assisted 11" rear drum brakes, and the front brakes are from a much earlier General Motors product, (that way when I received the truck), I have a real brake salad going!

Thanks, David

Note;
It also has occurred to me that some people may be put off by taking these great liberties in modifying such a rare truck. My decisions are based on time, money and the mechanical condition of the truck when I received it. If I am offending anyone, please let me know.

David ..
It is your truck and as such you are really going to enjoy driving it..
You do what you must for safety and ease of driving..
I fully believe that to save it ,modified or not from original is a blessing..
I would only get upset if some one ,knowingly, would try to pass it off as original..then the sparks would fly..other than that ..you have my blessings..the hell with the rest of them..Enjoy..

Mike Timoshyk · #5 16-02-09, 18:56

Hi Dave,

Do what you have to keep it safe and on the road. I don't really think there are really too many complete originals around. If someone asks me "why didn't you keep it completely original", I reply that once a vehicle has left the factory it is no longer original, besides, you wouldn't have had the pleasure and opportunity to see and "inspect" this vehicle because it would have to remain in the garage for years to track down any exisiting parts that needed replacement.

Cheers from The home of the Ford CMP/Blitz....Windsor Ontario

Mike Timoshyk

42 F15A
42 MB
52 M38

Lang · #6 22-02-09, 11:47

David and Ian,

I agree that this is a good modification which nobody can easily see but adds to safety. Just a comment about servos - I am a great believer in them having fitted one to my WC53 Dodge Carryall standard master cylinder. The difference was amazing, it actually stops like a normal vehicle!

This modification is bloody dangerous on Jeeps because of the axle twist pulling the steering bell-crank and of course the steering, causing violent swerving in an emergency stop. A safe jeep is one with lousy brakes!

The Jeep one being looked at on this thread is worth trying without a boost servo as combinations of sizes between master and wheel cylinders are a little tricky (but easily worked out by a bit of simple maths before fitting).

Your suggestion about boring the master cylinder(s) larger would make the pedal harder to push, not easier. This is the principle of hydraulic devices such as rams, jacks and brakes - the greater the difference between the surface area of the the pushing ram (master cylinder) and surface area of the lifting ram (wheel cylinders) the easier and more powerful it is.

Of course a master cylinder of 1/4 inch bore would be as light as a feather to lock the brakes but unfortunately the pedal would have to start its travel about your armpit to push enough volume of fluid into the wheel cylinders to move them. You see this effect in normal systems when the brakes are not adjusted up closely and the pedal goes down a long way to operate them.

Lang

David DeWeese · #7 16-03-09, 07:06

Hi,
Finally had a weekend to devote to the C8. Put the time to good use by test-fitting my 235 and a transmission to make sure everything was OK before painting the frame.
Both my donor 4-speed crash boxes turned out to be worn completely out, so resorted to Plan B:
Installed a six cylinder bellhousing from a '60 through '62 Chev truck which has the clutch fork exiting the right-hand side. Now I can use my stock C8 clutch linkage with a bellhousing that accepts the later model GM manual transmissions. Made up a couple of adapters to mount it so not to modify the original C8 crossmember.
Was then able to install a General Motors SM 420 4-speed transmission. First is the ultra-low "granny" gear that I will probably never use, but it now gives me three synchronized foreward gears to work with.
Next weekend I will tear it all back apart to prepare the frame for paint!

Regards, David

Bob Carriere · #8 16-03-09, 17:13

HI David

Do you happen to have the part number for that particular 1960 / 62 bell housing.....

I had considered the same arrangement with a C15A....but.... the modern 4 speed tranny and bellhousing left too little room between the transfer case and the tranny to properly connect with a short driveshaft. Moving the T case bad was not an option I wanted to exercise.

Fortunately for you the C8 lends itself to the conversion you did.

Bob C.

David DeWeese · #9 17-03-09, 06:42

Hi Bob,
The bellhousing is a used one I pulled out of a 1960 Chev 1/2 ton. It had a hydraulic slave cylinder mounted to the right hand side. Had one of the 3-speed column shift transmissions behind it. Uses a longer clutch fork also.
A friend has a factory parts manual for this model, so I'll try to get parts numbers for you.
Thanks, David

maple_leaf_eh · #10 17-03-09, 15:21

I wouldn't expect too many North American vehicles have clutching parts coming out the right side. All our vehicles are left-seat drive. Why would Detroit choose to put it on the right at all? Column shifter linkages ... ?

David DeWeese · #11 17-03-09, 15:45

Hi Terry,
Was wondering the same thing myself. The earlier GM trucks had the same transmission and column shift linkage, but kept the left hand clutch fork location. Since they went to the hydraulic slave cylinder that year, maybe they were concerned about exhaust temperatures.
Thanks, David

Bob Carriere · #12 17-03-09, 16:54

HI Terry / David

The change over was common in North America in the early sixties and I believe originated with the necessity/simplification of operating a clutch system for van type with a semi cabover condfiguration. Brake pedals had already changed over a decade before from solid linkage through the floor to a firewall mounted pedal attched directly to the master cylinder in the engine compartment.

The simplicity (until you have to bleed the darn system) of the hydraulic clutch linkage, allowed them to instal it on the right hand side. Once configured for vans the same concept was kept for pick up trucks.... not sure about the heavier Chev/GMC model. With the advant of automatic and electronically controlled transmission.... mechanical linkages are a thing of the past.

I need the part # to see if I can track one in our neighbourhood for possible future use....

BooBee