Help I.D. this brake booster and recommend dual master cylinder please

[CPO1]

This topic is discussed alot and I've read most of them. I come away with some confusion still so here's my specific situation.

This booster on my 65 GMC and the PO added it in 1990 or so. Has drum/drum. The engine is a small block V8 that's got a bit of a cam. I find the truck starts out braking like it is powerless then as i apply pressure it begins to brake better. Regardless that single master has to go and i have to run some vacuum testing yet. At this point, I think the booster is working properly but I am unsure how much vacuum I'm working with.

My questions

Is there a better booster for a cammed engine?

What dual master would fit this one I have now?

Or If I should replace it, with what?

Thanks.

[LT1 Burb]

I wonder if you have a vaccum leak where that goes into the master, any 67-72 master will fit.

[CPO1]

Originally Posted by LT1 Burb

I wonder if you have a vaccum leak where that goes into the master, any 67-72 master will fit.

Yes, Thank you. I plan to pull the truck out this week since the snow is gone now and test for leaks.
I'd like to know more about that booster. It would have come from a wrecker before 1990ish.
I read that dual chamber boosters are better for cammed engines but I don't know what booster have. The cam pretty lumpy I can say. It's in my budget to completely replace the booster/master combo with a new kit, that way I can be sure it's a match.

Anybody else? Thanks

[Captainfab]

Judging by the looks of the booster and the fact that it is chromed, I would say it is an aftermarket universal booster. It is hard to tell from the picture if it is a dual diaphram booster or a single. If your engine is low on vacuum, a dual diaphram booster will help as well as going with as large a diameter as you can.

To be able to use a '67-'70 truck master cylinder, you need to have the long intermediate pushrod. If you change to a new aftermarket universal booster it will likely have a short pushrod and you will need to use a master cylinder for a '70 Buick Estate wagon. An alternative would be to change over to a booster and master cylinder for a '67-'70 truck. I believe a booster for a C20 may work better with your low vacuum engine. The '67-'72 booster is one of the many boosters that are compatible with my booster brackets. My booster brackets are designed to use the factory mounting holes, which maintains a good solid connection between the booster/master cylinder and the pedal bracket on the inside of the firewall.

[CPO1]

Originally Posted by Captainfab

Judging by the looks of the booster and the fact that it is chromed, I would say it is an aftermarket universal booster. It is hard to tell from the picture if it is a dual diaphram booster or a single. If your engine is low on vacuum, a dual diaphram booster will help as well as going with as large a diameter as you can.

To be able to use a '67-'70 truck master cylinder, you need to have the long intermediate pushrod. If you change to a new aftermarket universal booster it will likely have a short pushrod and you will need to use a master cylinder for a '70 Buick Estate wagon. An alternative would be to change over to a booster and master cylinder for a '67-'70 truck. I believe a booster for a C20 may work better with your low vacuum engine. The '67-'72 booster is one of the many boosters that are compatible with my booster brackets. My booster brackets are designed to use the factory mounting holes, which maintains a good solid connection between the booster/master cylinder and the pedal bracket on the inside of the firewall.

Captainfab,
I never considered the possibility of an aftermarket universal booster. I thought the PO (my deceased brother) found something from a wrecker then sent it out for chroming with all the other chromed parts under this hood.

As far as sourcing the replacement parts you suggest, will my local NAPA or other parts store carry them or will I have to turn to a specialty reproduction outfit??

Here's a side shot if that helps- what are the tell tale differences?? I read about your bracket a while back and will definitely be contacting you.

[canadian_diesel1964]

I have a 51 Ford F1 with a big cam(chev 350) and I had same issue till I added an auxillary vacuum canister to have a build up of vac for the brakes...sure did the trick..

[CPO1]

Originally Posted by canadian_diesel1964

I have a 51 Ford F1 with a big cam(chev 350) and I had same issue till I added an auxillary vacuum canister to have a build up of vac for the brakes...sure did the trick..

Good to know, Thanks.

[donthekawguy]

I have a big cam in mine and I'm using a booster and MC from a 71 Impala. No issues at all.

[Captainfab]

With my booster bracket, the above suggested parts can be sourced from either a wrecking yard or your local auto parts supplier. No need to purchase any specialty parts.

[64shortbox]

I would definitely go with Captainfab's Booster Bracket. I purchased one from him and it looks like a factory piece and as Captainfab said fits most any GM vacuum booster. I used a booster from a late 80's Chevy truck but now plan on going with a smaller dual diaphragm booster from an early Chevy Astro Van, same bolt pattern on both. I'm sure his bracket will work with your chrome aftermarket vacuum booster and when done it will look like a factory bracket, a nice, neat, clean installation.

[Captainfab]

Thank you

Originally Posted by 64shortbox

I would definitely go with Captainfab's Booster Bracket. I purchased one from him and it looks like a factory piece and as Captainfab said fits most any GM vacuum booster. I used a booster from a late 80's Chevy truck but now plan on going with a smaller dual diaphragm booster from an early Chevy Astro Van, same bolt pattern on both. I'm sure his bracket will work with your chrome aftermarket vacuum booster and when done it will look like a factory bracket, a nice, neat, clean installation.