New Power Brake Booster - NOT BOOSTING !!!

[Steve Hafner]

. . . .

During my 1970 350's restoration, a new booster / master cylinder was installed and front disc's were added. I can hear the rush of air when the vacuum line is pulled off and the hose is connected to a good source.

The pedal doesn't feel like "power brakes" - the truck stops a little better now, but that's probably because of the added front disc's.

It just doesn't feel like what I remember power brakes in the 70's were like.

Does anyone have anymore ideas of what to check ?

. . . .

[ChevLoRay]

What about the push rod from the pedal to the master cylinder? Is there a difference between PB and non-PB rod? It seems I recall in some apps, that there is a difference. It may not be so, but it's just a question.

My truck had power brakes before the conversion, so I can't answer my own question.

Who was your supplier? If it is ECE, give 'em a call. They were good to answer issues for me.

[Steve Hafner]

Originally Posted by ChevLoRay

What about the push rod from the pedal to the master cylinder? Is there a difference between PB and non-PB rod? It seems I recall in some apps, that there is a difference. It may not be so, but it's just a question.

My truck had power brakes before the conversion, so I can't answer my own question.

Who was your supplier? If it is ECE, give 'em a call. They were good to answer issues for me.

I didn't do the installation, but the rod seemed to work properly - I asked the guy who did the work to adjust the pedal a little closer to the floor ( like power brake pedals should be ) He drove it a few times before I picked it up and he said, "I was going to love the power brakes" !! Then when he delivered it to me, he said the brakes didn't seem as "touchy" as they were at first.

It was purchased at CPP ( Classic Performance Parts )

If know body else on here has any ideas, I guess I'll have to call them and see what they say.

[Wrenchbender Ret]

I have the same thing. I bought mine from CPP also. It is a Delco Moraine new unit. I just have been liveing with it for 2-3 years now. It stops OK & has a good pedal but like you say it just doesn't feel like power brakes. Let us know what happens. They have a lifetime warranty.

[AustinScott]

got any pictures of your boosters? Is it a single or duel diaphragm?
Also might want to check the amount of VAC you have at the booster, might be building some pressure, but maybe not enough to take full advantage of the boosters ability.

[Steve Hafner]

Originally Posted by AustinScott

got any pictures of your boosters? Is it a single or duel diaphragm?
Also might want to check the amount of VAC you have at the booster, might be building some pressure, but maybe not enough to take full advantage of the boosters ability.

Thanks !!! I'll have to have someone check the vacuum for me.

Here's a picture from CPP, where I bought it. Mine looks just like this and is for a disc - drum setup.

That rod on the far right was adjusted to have a fairly low pedal.

I'll attach a picture of the interior to show the pedals height too, it's not REAL low - just lower then it was with manual brakes.

. . . .

[rsavage]

There is a small rod that goes from the booster to the back of the MC. It is adjustable. You must unbolt the MC (you should be able to leave your lines hooked to it) and move it forward enough to see the rod. The end of the rod can be adjusted out (5/16" wrench if I remember correctly) to increase the role of the booster. Too much out will have your brakes dragging. You have to adjust some, try it out, and maybe readjust. The inside pedal rod does nothing to adjust the booster.

[Steve Hafner]

Originally Posted by rsavage

There is a small rod that goes from the booster to the back of the MC. It is adjustable. You must unbolt the MC (you should be able to leave your lines hooked to it) and move it forward enough to see the rod. The end of the rod can be adjusted out (5/16" wrench if I remember correctly) to increase the role of the booster. Too much out will have your brakes dragging. You have to adjust some, try it out, and maybe readjust. The inside pedal rod does nothing to adjust the booster.

THANKS !!! We will try this and I'll report back to you !!!

[eurospec1]

Originally Posted by Steve Hafner

THANKS !!! We will try this and I'll report back to you !!!

Also, is your motor stock? A larger then stock cam will create less vacuum, and sometimes not enough to run power brakes

[Steve Hafner]

Originally Posted by eurospec1

Also, is your motor stock? A larger then stock cam will create less vacuum, and sometimes not enough to run power brakes

Yes, it's stock and has 200,000 miles on it.

[Steve-W]

what brand brake disks and pads are you using? wrong pads will definitly give you that feel, like they're just not digging in or like you've burned you're pads.
the brake paddle will still feel rock hard, but there's just no responds.

[cleszkie]

Did you upgrade your proportioning valve for disc brakes up front? If not, you need to do this to get the proper fluid flow to the front calipers.

[Steve Hafner]

Originally Posted by cleszkie

Did you upgrade your proportioning valve for disc brakes up front? If not, you need to do this to get the proper fluid flow to the front calipers.

Yes, it's the correct valve for disc brakes ( at least that what was ORDERED )