Is it a simple swap from manual brakes to power brakes in a '71 GMC P/U? - The 1947 - Present Chevrolet & GMC Truck Message Board Network

GiMiCs · 11-21-2008, 04:23 AM

Hi again! Was wondering if it'll be fairly easy to install a power brake unit (booster and master cyl. came shipped together...), in place of my existing
manual brake master cyl.? Will lines match up? Will the system line up ok w./ the existing brake pedal? Should I bench bleed the master cyl.? I always did on other vehicles, but since this unit is already bolted together, I'm wondering if it was done at the factory, or should I be on the safe side , and unbolt the master cyl. from the booster and bench bleed it anyway ? Thanks for your help, as I've never done this swap on GMC/ CHEVYS before!

JimKshortstep4x4 · 11-21-2008, 06:38 AM

It is pretty simple to install power brakes. The lines should line up but if they are rusty I would suggest replacing them.

You will need the booster mounting brackets, booster braces, and linkage including the brake pedal rod.

Bench bleeding will speed up the bleeding process or you can gravity bleed the system after installation.

Bleeding the system will be necessary anyway.

Jim

Tx Firefighter · 11-21-2008, 09:48 AM

There is no need to unscrew any lines or do any bleeding when doing this swap unless your current master cylinder is bad.

I'd just unbolt your current master cylinder from the firewall and leave the lines hooked up. Add the boooster between the master and the firewall and bolt it back in place.

It's always worked for me.

70GMCer · 11-21-2008, 10:02 AM

Quote:

Originally Posted by Tx Firefighter

There is no need to unscrew any lines or do any bleeding when doing this swap unless your current master cylinder is bad.

I'd just unbolt your current master cylinder from the firewall and leave the lines hooked up. Add the boooster between the master and the firewall and bolt it back in place.

It's always worked for me.

That's how I did mine until the time came to do the disk conversion.

JimKshortstep4x4 · 11-21-2008, 09:46 PM

On the manual trucks that I have taken apart the brake rod from the brake pedal is long and tapered where it fits into the master cylinder, (pic attached for reference). The boosters that I have removed have a very short rod sticking out of them. My question is, how does the booster rod match up to a master cylinder that is bored for a long tapered rod?

Jim

Tx Firefighter · 11-21-2008, 10:42 PM

Jim,

The master cylinders are the same between manual and power brake trucks.

Keep in mind that the longer manual brake pushrod only actually sticks a short way past the actual firewall. By the time the pushrod goes from the pedal through the firewall, there is only a short stub protruding past the firewall, just like the power booster has a short pushrod.

I did an FAQ a few years ago covering this. I just removed the manual pushrod and added the booster, reusing the master cylinder and not even breaking loose any lines. I'm sure it's buried somewhere on the board here.

GiMiCs · 11-22-2008, 12:23 AM

Thanks for your expertise guys! I do have to replace the master cyl. so I bought them already bolted together, then realized I might need extra brackets for the booster,-etc; as you said Jim!? The lines are rusty, so I'm looking for a ready made kit as I'm asking about on another post herein, as they seem to have 2 or even 3 diff. diameters on the brake lines!! I usually make my own lines so I know what I'm "getting" *wink*, BUT these diff. sizes, and connecting blocks that are rusted almost thru are just too much hassle to be worth making them now that it's cold out BRRRR!!!-LOL! Glad to know the rod sizes/lengths are similar as that was my other major concern! Thanks again!!!

GMCMAX · 11-22-2008, 12:49 AM

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

GiMiCs · 11-22-2008, 01:41 AM

Thanks a MILLION GMCMAX!!! I panicked when I saw your parts list and pic. RE: the pwr. booster's bracket, and ran down stairs to see if I took it off the '72 Jimmy?(Suburban) that I pulled the V-8 out to dump in my '71 P/U. Luckily I save it, and hopefully the check valve is still somewhere around too!-lmao!!! I'm hoping the jimmy's bracket is the same one I'll need for My 1500 P/U ?!? If not, it should be close enough I can "shim" it up somehow-lol- It will be nice to have POWER brakes, as the manual master cyl. made me feel like Fred Flintstone when I needed to stop REALLY fast! --

:

11-21-2008, 04:23 AM	#1
GiMiCs Registered User Join Date: Sep 2008 Location: new haven, CT. Posts: 9	Is it a simple swap from manual brakes to power brakes in a '71 GMC P/U? Hi again! Was wondering if it'll be fairly easy to install a power brake unit (booster and master cyl. came shipped together...), in place of my existing manual brake master cyl.? Will lines match up? Will the system line up ok w./ the existing brake pedal? Should I bench bleed the master cyl.? I always did on other vehicles, but since this unit is already bolted together, I'm wondering if it was done at the factory, or should I be on the safe side , and unbolt the master cyl. from the booster and bench bleed it anyway ? Thanks for your help, as I've never done this swap on GMC/ CHEVYS before!

11-21-2008, 06:38 AM	#2
JimKshortstep4x4 Senior Member Join Date: Jul 2001 Location: Muskegon,MI,USA Posts: 6,026	Re: Is it a simple swap from manual brakes to power brakes in a '71 GMC P/U? It is pretty simple to install power brakes. The lines should line up but if they are rusty I would suggest replacing them. You will need the booster mounting brackets, booster braces, and linkage including the brake pedal rod. Bench bleeding will speed up the bleeding process or you can gravity bleed the system after installation. Bleeding the system will be necessary anyway. Jim __________________ 1971 Shortbox step side 4x4, 350 sbc, 3:07 rear end 1965 Impala SS 400 sbc, Muncie rock crusher 1966 Impala SS 396 bbc, TH 400 1969 El Camino, 350 sbc, TH 350 1971 Snowplow built on a Blazer frame 1972 GMC Short bed, stepside, TH 400, 427 BBC

11-21-2008, 09:48 AM	#3
Tx Firefighter Watch out for your cornhole ! Join Date: Jun 2003 Location: Azle, Texas Posts: 14,162	Re: Is it a simple swap from manual brakes to power brakes in a '71 GMC P/U? There is no need to unscrew any lines or do any bleeding when doing this swap unless your current master cylinder is bad. I'd just unbolt your current master cylinder from the firewall and leave the lines hooked up. Add the boooster between the master and the firewall and bolt it back in place. It's always worked for me. __________________ I'm on the Instagram- @Gearhead_Kevin

11-21-2008, 09:46 PM	#5
JimKshortstep4x4 Senior Member Join Date: Jul 2001 Location: Muskegon,MI,USA Posts: 6,026	Re: Is it a simple swap from manual brakes to power brakes in a '71 GMC P/U? On the manual trucks that I have taken apart the brake rod from the brake pedal is long and tapered where it fits into the master cylinder, (pic attached for reference). The boosters that I have removed have a very short rod sticking out of them. My question is, how does the booster rod match up to a master cylinder that is bored for a long tapered rod? Jim Attached Images __________________ 1971 Shortbox step side 4x4, 350 sbc, 3:07 rear end 1965 Impala SS 400 sbc, Muncie rock crusher 1966 Impala SS 396 bbc, TH 400 1969 El Camino, 350 sbc, TH 350 1971 Snowplow built on a Blazer frame 1972 GMC Short bed, stepside, TH 400, 427 BBC

11-21-2008, 10:42 PM	#6
Tx Firefighter Watch out for your cornhole ! Join Date: Jun 2003 Location: Azle, Texas Posts: 14,162	Re: Is it a simple swap from manual brakes to power brakes in a '71 GMC P/U? Jim, The master cylinders are the same between manual and power brake trucks. Keep in mind that the longer manual brake pushrod only actually sticks a short way past the actual firewall. By the time the pushrod goes from the pedal through the firewall, there is only a short stub protruding past the firewall, just like the power booster has a short pushrod. I did an FAQ a few years ago covering this. I just removed the manual pushrod and added the booster, reusing the master cylinder and not even breaking loose any lines. I'm sure it's buried somewhere on the board here. __________________ I'm on the Instagram- @Gearhead_Kevin

11-22-2008, 12:23 AM	#7
GiMiCs Registered User Join Date: Sep 2008 Location: new haven, CT. Posts: 9	Re: Is it a simple swap from manual brakes to power brakes in a '71 GMC P/U? Thanks for your expertise guys! I do have to replace the master cyl. so I bought them already bolted together, then realized I might need extra brackets for the booster,-etc; as you said Jim!? The lines are rusty, so I'm looking for a ready made kit as I'm asking about on another post herein, as they seem to have 2 or even 3 diff. diameters on the brake lines!! I usually make my own lines so I know what I'm "getting" wink, BUT these diff. sizes, and connecting blocks that are rusted almost thru are just too much hassle to be worth making them now that it's cold out BRRRR!!!-LOL! Glad to know the rod sizes/lengths are similar as that was my other major concern! Thanks again!!!

11-22-2008, 12:49 AM	#8
GMCMAX Active Member Join Date: Jan 2006 Location: Lower Mid-East Ca. Posts: 326	Re: Is it a simple swap from manual brakes to power brakes in a '71 GMC P/U? 69 I swapped http://67-72chevytrucks.com/vboard/s...d.php?t=221598 __________________ Never try to teach a pig to sing; it wastes your time and annoys the pig! Gets More Chicks My lugnuts require more torque than your honda makes! 68 GMC, 4X4 conversion w/73 k20 running gear and springs, 350 4spd, 4.10's, D44 powerlok front, 14BFF govlock rear, 33" tires, lifted 4".

11-22-2008, 01:41 AM	#9
GiMiCs Registered User Join Date: Sep 2008 Location: new haven, CT. Posts: 9	Re: Is it a simple swap from manual brakes to power brakes in a '71 GMC P/U? Thanks a MILLION GMCMAX!!! I panicked when I saw your parts list and pic. RE: the pwr. booster's bracket, and ran down stairs to see if I took it off the '72 Jimmy?(Suburban) that I pulled the V-8 out to dump in my '71 P/U. Luckily I save it, and hopefully the check valve is still somewhere around too!-lmao!!! I'm hoping the jimmy's bracket is the same one I'll need for My 1500 P/U ?!? If not, it should be close enough I can "shim" it up somehow-lol- It will be nice to have POWER brakes, as the manual master cyl. made me feel like Fred Flintstone when I needed to stop REALLY fast! --:



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