# '65 GTO hard pedal



## adamrysz87 (Nov 14, 2021)

Hello, in my '65 GTO I have a problem because the pedal is hard all the time, nothing changes when I start the engine. The car does not brake at all ...

I bought the GTO after an accident with the Wilwood kit installed, with front and rear discs.

I have a few questions. Below are some explanatory photos.

1. Do I have the wires connected to the power booster well? Vaccum from the manifold to the black can, from the black can to the power booster. (without the can I don't feel the difference).

2. Why was someone giving a black can?

3. What should the vacuum be if I wanted to measure it?

4. Do you have any idea where the problem could be?


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## GTOJUNIOR (Aug 7, 2011)

The vacuum canister (BLACK CAN) is needed when you have a low vacuum issue.
This is usually related to camshaft choice, the vacuum needed is somewhere around 15 inches. 
Do you know what cam you have?


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## PontiacJim (Dec 29, 2012)

Not much info to go on.

First, look like the original owner added the auxiliary vacuum can because the engine had low vacuum.

With a bigger than stock cam, engine vacuum can drop like a stone - so power brakes may not work as they operate off engine vacuum. So test engine vacuum first. Then let us know.

1965 had a single reservoir master cylinder, so you may have several things gong on if the original installer did not know his ass from his elbow and read some article in Hot Rod magazine on how to do the conversion. So you need to start from ground zero and check everything to include emailing Wildwood to make sure you have the correct kit/parts and it all matches and is not piecemealed together.

Not sure how the vacuum hoses are connected to the power booster. That fitting on the left, looking at the pic, is where the vacuum line hooks up which typically pulls off a fitting/nipple on the back of the carb. Looks like you might have it hooked to the intake manifold fitting? Assume it pulls vacuum off the intake fitting, goes to the auxillary vacuum can, then back out to the power brake booster? No hose clamp to secure the hose?????? Make sure you are using vacuum hose, not gas line as maybe it is collapsing - providing you have enough engine vacuum. A formed steel line would be better than all that rubber hose and then use just a small rubber hose coupling.

A lot of these aftermarket "kits" and "parts" seem to be a problem more than not. You must have the correct master cylinder bore for the brakes. A large bore will move more fluid, but requires a lot more pedal effort and will feel hard. A smaller bore MC will move less fluid, but develop more pressure and make an easier feeling pedal - down side is that it may not hold enough fluid in the bore and this means the brakes will not fully engage.

Brake pedal geometry is also important - ie leverage. Pontiac used a different brake pedal for non-power vs power brakes. Some will have two holes and you have to swap them, but I think the '65 used a specific pedal for each - but I am no expert on '65's. You also need to measure the rod that goes into the back of the booster that operates it - wrong length can cause issues.

You should have a proportioning valve/block that balances the braking force front/rear. If a late model factory valve was used, there is a check valve inside that needs to be "centered" and if it moves left or right of center, it is designed to shut the brake fluid off the the line which has the lower pressure - ie the brake line develop a leak the valve isolates it so you still have the other brake line to stop the car - thus dual reservoir master cylinder is a safety feature.

I would also pull all wheels and make sure the brakes are compressing against the discs. If it has been sitting, the pistons could be frozen. I would also crack each bleeder (which should be on top of the caliper if installed correctly) and push the pedal to make sure fluid is flowing. Then do a complete bleeding of the brakes. Some of those kits also don't fit as advertised - brackets hit or jam the brakes. Most disc brakes require 15" or larger rims so check clearances in depth and inside dimensions of the rim.

Also possible you have defective parts.


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## BLK69JUDGE (Jun 10, 2010)

hmmmmmmmm

to me...

it looks like the vacuum is hooked up to the pcv fitting on the runner in front of the carb

I thought we got vacuum off the rear of the carb baseplate ??

howzabout a picture of the carbonator with the air filter off,,,, 

where is your pcv hose going ?

what carb r u running etc


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## PontiacJim (Dec 29, 2012)

BLK69JUDGE said:


> hmmmmmmmm
> 
> to me...
> 
> ...


If you look to the left of that brass fitting with the hose on it, it appears to be the PCV hose just behind it going to the carb base - dark picture and hard to see.

I also don't like those small mini brake boosters.


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## RMTZ67 (Mar 12, 2011)

Try replacing the check valve on the booster before tearing into the car. They are not tha expensive. The one on the end of the hose that plugs into the booster.


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## LATECH (Jul 18, 2018)

without a vacuum check valve in the hose to the black can, it is useless
A dual diaphram booster is useless
without the correct piston size ratio between the master and the calipers, wilwoods are useless
Post the piston quantity and diameter for the fronts and rear and the diameter of the master cylinder.Also knowing the pushrod ratio at the brake pedal would be helpful


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## BLK69JUDGE (Jun 10, 2010)

Jim
ah yes I see it now ...
but guys
a hard pedal seems to be a vacuum issue not master cylinder issues
It seems to me he is explaining his brakes are similiar to the car NOT
running... and a hard pedal ,,, ?? I would still move the vacuum source to the rear of the carb and not on an intake runner ....

Scott


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## RMTZ67 (Mar 12, 2011)

I agree with Blk69judge...move the vacuum to the rear of the carb. If that don't fix it, add a new check valve on the booster. Two easy/cheap fixes and go from there.


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## LATECH (Jul 18, 2018)

Try adding a check valve to the cheesy black can first.It is doing NOTHING.
OR , have you checked for vacuum at the booster?
Maybe the can has a check and it is installed backerds?


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## PontiacJim (Dec 29, 2012)

LATECH said:


> Try adding a check valve to the cheesy black can first.It is doing NOTHING.
> OR , have you checked for vacuum at the booster?
> Maybe the can has a check and it is installed backerds?



Looks like the vacuum can is this one. Has the check valve like a brake booster. I am thinking the hoses are connected reverse looking at the photo. The manifold hose is hooked to the straight brass nipple on the tank. I am thinking it should be connected to the check valve and then a hose from the brass nipple to the brake booster?









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## LATECH (Jul 18, 2018)

Yep.Hooked up Backerds


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## LATECH (Jul 18, 2018)

PontiacJim said:


> The manifold hose is hooked to the straight brass nipple on the tank. I am thinking it should be connected to the check valve and then a hose from the brass nipple to the brake booster?
> 
> 
> 
> ...


Exactly. No vacuum getting anywhere.Maybe OP did not think to check for vacuum at the booster?


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## adamrysz87 (Nov 14, 2021)

Thanks guys for the answers and your interest.
Jim, the connection is correct. The vacuum is connected to the check valve, then a hose from the brass nipple to the brake booster.

But I changed the vacuum connection point. Now I connected the hose to the back of the carburetor and there is a difference. The brakes work better, but they are still not sharp, is that already the case in old cars?

What do you think about changing the PCV connection? Now it is the front of the carburetor, I am thinking of connecting to air cleaner.

(Photos before changing the vacuum connection)


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## LATECH (Jul 18, 2018)

E Gad man. A chevrolet carb on a PONTIAC......LOL


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## gkraushaar (Oct 4, 2020)

adamrysz87 said:


> Hello, in my '65 GTO I have a problem because the pedal is hard all the time, nothing changes when I start the engine. The car does not brake at all ...
> 
> I bought the GTO after an accident with the Wilwood kit installed, with front and rear discs.
> 
> ...


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## gkraushaar (Oct 4, 2020)

When I switched to front disks, I had the same issue-hard pedal due to lack of vacuum to move the disk pistons. My cam (Edelbrock Performer package) took too much vacuum, so I added an electric vacuum pump-vane style from LEEDS and now I have over 17 hg of vacuum. You need a proportioning valve, too to balance the pressure between the drums and the disks. The LEEDS is quiet and provides added vacuum. It stops great now.


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