Power brake conversion

[BigBlockNBK]

Sorry if these questions are posted elsewhere. I am wanting to convert my 1970 C20 Panel from manual brakes to power brakes. I have the booster and new master already but looking at it the bolts for the pedal assembly that go thru the firewall are welded to the bracket, but the booster studs need to go thru the firewall in the opposite direction. So Im wondering if i should take it out and cut the bolts off or are there any other things that are different that are just gonna cause problems after I do that. Should I just get a pedal assembly off of a power brake vehicle? also the hole is in a different place for the rod that goes to the pedal so am I gonna run into something else when I cut the hole? Any thing else different about the manual brake and power brake trucks I should know about?

Another thing I want to do is drop the front 2 inches any pros/cons to doing it with drop springs or drop spindles?

I also plan on converting the front to disc brakes, I read on another site u can use '73-87 spindles and parts if u change the ball joints and tie rod ends. Has anyone done this? I have also seen where you can move spindles from one side to the other and flip it upside down to get the drop. yes/no? pros/cons?

Im sure I will have more questions once this thread gets going. thanks

[LockDoc]

Originally Posted by BigBlockNBK

Sorry if these questions are posted elsewhere. I am wanting to convert my 1970 C20 Panel from manual brakes to power brakes. I have the booster and new master already but looking at it the bolts for the pedal assembly that go thru the firewall are welded to the bracket, but the booster studs need to go thru the firewall in the opposite direction. So Im wondering if i should take it out and cut the bolts off or are there any other things that are different that are just gonna cause problems after I do that. Should I just get a pedal assembly off of a power brake vehicle? also the hole is in a different place for the rod that goes to the pedal so am I gonna run into something else when I cut the hole? Any thing else different about the manual brake and power brake trucks I should know about?

Another thing I want to do is drop the front 2 inches any pros/cons to doing it with drop springs or drop spindles?

I also plan on converting the front to disc brakes, I read on another site u can use '73-87 spindles and parts if u change the ball joints and tie rod ends. Has anyone done this? I have also seen where you can move spindles from one side to the other and flip it upside down to get the drop. yes/no? pros/cons?

Im sure I will have more questions once this thread gets going. thanks

As far as the booster you must be missing the bracket and linkage assembly that goes between the booster and firewall. The under dash pedal assemblies are all the same. You need to get a complete booster assembly off of a '68-'72 truck to make sure you have all of the correct parts to install it. Make sure it has the rod that goes from the booster linkage to the brake pedal. Here are a couple of threads that may help....

http://67-72chevytrucks.com/vboard/s...d.php?t=353088

http://67-72chevytrucks.com/vboard/s...d.php?t=221598

I can't help too much on the spindles questions because I always change the whole front cross member to the later one. Just easier for me.

Here is a thread on the spindle swap that may give you the info you need.

http://67-72chevytrucks.com/vboard/s...68&postcount=4

LockDoc

[BigBlockNBK]

Yup there is that bracket on the booster I am missing. That should make it a lot easier once I find that.

I happened to find a 71 or 72 disc brake truck in a salvage yard today so I grabbed the whole spindle assemblies off of the front end. No metering block though.

Thanks

[LockDoc]

Originally Posted by BigBlockNBK

Yup there is that bracket on the booster I am missing. That should make it a lot easier once I find that.

I happened to find a 71 or 72 disc brake truck in a salvage yard today so I grabbed the whole spindle assemblies off of the front end. No metering block though.

Thanks

Good find!

If you need to look the block up it is called a proportioning valve. Let us know if you have any more questions.

LockDoc

[BigBlockNBK]

Yup thats what I meant, any idea what the crossover would be? Would proportioning valves off of trucks after 72 work? Is there a difference between 1/2 ton and 3/4 ton valves?

Any idea if the ball joints are the same on drum and disc trucks?

I also am wanting to put a serpentine setup on it, any idea if a setup off of a 87 and newer smallblock would work? I would imagine so but I dont know for sure if any of the boltholes changed when they want to center bolt valve covers

Thanks

[BigBlockNBK]

Any idea on how wide of a tire can fit in the rear? Wheel width? Backspacing?

Any opinions on pros vs cons for drop springs or drop spindles for the front?

[LockDoc]

Originally Posted by BigBlockNBK

Yup thats what I meant, any idea what the crossover would be? Would proportioning valves off of trucks after 72 work? Is there a difference between 1/2 ton and 3/4 ton valves?

I would buy the valve for the booster/master I was using. I don't know about the 1/2 and 3/4 .

Any idea if the ball joints are the same on drum and disc trucks?

This thread should tell you anything you want to know about drum/disk conversion.

http://67-72chevytrucks.com/vboard/s...d.php?t=456889


I also am wanting to put a serpentine setup on it, any idea if a setup off of a 87 and newer smallblock would work? I would imagine so but I dont know for sure if any of the boltholes changed when they want to center bolt valve covers

No idea on this....

Thanks

Originally Posted by BigBlockNBK

Any idea on how wide of a tire can fit in the rear? Wheel width? Backspacing?

Any opinions on pros vs cons for drop springs or drop spindles for the front?

http://67-72chevytrucks.com/vboard/s...d.php?t=597593

LockDoc

[BigBlockNBK]

According to Classic Performance Products the proportioning valve is the same from 71 to 77 and the same for 1/2 and 3/4 tons

[LockDoc]

Originally Posted by BigBlockNBK

According to Classic Performance Products the proportioning valve is the same from 71 to 77 and the same for 1/2 and 3/4 tons

Good info on that. Thanks.

LockDoc

[BigBlockNBK]

Ugh NONE of the brake lines have the same fittings. I knew I had to replace the front hoses and I was lucky to find the lines from the Master to the Proportioning valve. Not sure yet what I am gonna do about the rest of the lines.

[BigBlockNBK]

I found adapters for the proportioning valve to the brake lines.

So I put the rotors on the front and the old drums had 1/2" studs and now the discs have 9/16 studs. Awesome. Any idea if either of those can be changed to the other?

So I know I have to put the newer tie rod ends on, but am I gonna have to change the draglink also?

So my panel has a plywood floor did they ever have the wood slats like a truck bed or is that a not too difficult conversion to do?

[BigBlockNBK]

Well the 1970 draglink worked. I bled the **** out of everything the manual way and with a mityvac. must still be some air trapped somewhere the brakes dont work very well and when I use the brakes the light comes on, any ideas?

[LockDoc]

Originally Posted by BigBlockNBK

I found adapters for the proportioning valve to the brake lines.

So I put the rotors on the front and the old drums had 1/2" studs and now the discs have 9/16 studs. Awesome. Any idea if either of those can be changed to the other?

The 1/2" can be drilled out to 9/16"

So I know I have to put the newer tie rod ends on, but am I gonna have to change the draglink also?

So my panel has a plywood floor did they ever have the wood slats like a truck bed or is that a not too difficult conversion to do?

My '67 Panel has the metal strips in the cargo area.

Originally Posted by BigBlockNBK

Well the 1970 draglink worked. I bled the **** out of everything the manual way and with a mityvac. must still be some air trapped somewhere the brakes dont work very well and when I use the brakes the light comes on, any ideas?

Did you start with the longest line and end with the shortest line to bleed them....

Bench bleeding the master cylinder is important if the whole system has been apart....

On the drum brakes, one thing I found on mine is when you put everything back together and adjust the brake shoes you can’t just adjust them out until they start rubbing and quit. You have to adjust them out as far as they will go and you cannot turn the wheel or drum at all. This centers the whole assembly in the drum. (I even tap around the drum as I tighten them to help them center themselves) Then you back them off until the wheel just turns, and stop. If you only adjust them out until they start rubbing and quit, the first time you press on the brake pedal the brake shoe assemblies will center themselves and you will have too much clearance between the shoes and the brake drum. I also put three lug nuts on backwards to hold the drum tight against the axle on the rear.

I know it is a pain in the butt to try and hold the self adjusters off of the adjuster wheel while you back them off, but this is the only way I could get my drum brake shoes adjusted correctly so I had good pedal.

LockDoc

[BigBlockNBK]

Yeah I did RR, LR, RF, LF. I would normally bench bleed the master but it didnt come with the kit to do it.

This is a C20 so you actually have to pull the axles out to get the drums off. I would normally use the slots in the backing plate to move the self-adjuster when I take it apart, but there are no slots on these so I have no access to it once I put the drums back on.

[LockDoc]

Originally Posted by BigBlockNBK

Yeah I did RR, LR, RF, LF. I would normally bench bleed the master but it didnt come with the kit to do it.

This is a C20 so you actually have to pull the axles out to get the drums off. I would normally use the slots in the backing plate to move the self-adjuster when I take it apart, but there are no slots on these so I have no access to it once I put the drums back on.

-
Are you sure there isn't a knockout plug on the front of the brake drums or on the backing plate? There should be an indentation where the knockout plug is and you just punch it out with a punch or chisel.

Sometimes they can be tough to punch out.

LockDoc

[BigBlockNBK]

So my old drms have the slot in them, the new ones dont. From the outside I cant see a knockout on the backing plate so I think I am gonna try drilling a hole in the backing plate.

[LockDoc]

Originally Posted by BigBlockNBK

So my old drms have the slot in them, the new ones dont. From the outside I cant see a knockout on the backing plate so I think I am gonna try drilling a hole in the backing plate.

Let us know if you run into any problems doing that.....

LockDoc

[BigBlockNBK]

Well that seemed to work, brakes work much better and the light doesnt come on anymore.

Anyone have an answer to the wheel backspacing question?

[LockDoc]

Originally Posted by BigBlockNBK

Well that seemed to work, brakes work much better and the light doesnt come on anymore.

Anyone have an answer to the wheel backspacing question?

Glad you got the brakes figured out. I can't help on the wheel/backspacing issue.... Maybe someone else will jump in on that.

LockDoc

[mdw]

For your serp. drive I took a complete unit out of a 1989 c1500, was a old state truck so it had no air conditioning but had an air pump. I cut down the bracket where the air pump was as I do not need it, this cleaned it up some, as far as bolting up, it all bolted up fine, the pulleys for the crank and w.p. work fine, I used the alternator off the 89 as it was a factory high amp one wire thus eliminating the ext. voltage regulator. I will be also using the newer p.s. pump as well as I am running a hydroboost so the hoses are going to be made up for that, you may be able to just swap the pulleys on the p.s. pump but I am not sure.

[BigBlockNBK]

I plan on using all the accessories from the donor truck. I think you have to use the water pump, dont serpentine's turn the opposite direction? Then you have the short and long water pump nonsense.

[BigBlockNBK]

Looking at buying some parts off of Craigslist to build my engine but I wanna make sure my plan will work. Does anyone see a problem with camelhump heads on a 400?

[BigBlockNBK]

Ok I decided to go with a 396, the problem is I cant find any Headers for a manual transmission truck, Does anyone know why automatic headers wont work?