Im sure the topic has been discussed before. I have a 64 jetstar with a 330 which ive rebuilt and installed a mondello cam jm 18/20. Switched to a 4 barrel qaudrajet and im experiencing low vacuum. I have power brakes with a single master cylinder. I want to switch to a dual master cylinder and add a vacuum canister. I just want a straight answer which master cylinder do i need to workqwith my booster. Part numbers appreciated.

 

I looked up the specs on that camshaft and it is fairly close to the UltraDyne cam that's in my engine:

• JM 18-20
• 0.488 Intake lift / 0.496 Exhaust Lift
• 260° Advertised Intake Duration/266° Advertised Exhaust Duration
• 216° Intake Duration @ .050 / 226° Exhaust Duration @ .050
• 112° Lobe Separation

My engine had slightly low idle vacuum with the UltraDyne cam (very bouncy about 15") and the power brakes didn't work very well. A lot of experimentation resulted in setting the initial timing to 18*, the vacuum advance connected to manifold vacuum, and this increased the idle vacuum and smoothed it out completely. Now the power brakes work great.

 

The dual master cylinder for a 1962-66 Cadillac bolts to your current booster and has a deep piston for the long pushrod in your current booster.

 

 

Will the above model work if i were to use a Cadillac master cylinder.

 

So, above I said 62-66 Cad, the applications for the M/C you posted are 62-66 Cad.

 

Ok i will go ahead and order it.

 

Is there any extra valves needed now. Im running drums on all 4. Also does it matter which port on the master cylinder runs to the front or rear brakes. Im seeing mixed opinions on this when i research. I was trying to find a good diagram on how to plumb. Finding only disc/ drum or disc/disc setups.

 

To answer your two questions, no and no

 

I would think 15” of vacuum would be enough to run a brake booster. Make sure the check valve in the vacuum hose is good. If you pull the valve out of the grommet with the engine off, you should get a pretty dramatic pop when you break the seal.

If 15 inches really isn’t enough, a vacuum storage canister tucked up inside the front wheelhouse (out of sight) should definitely solve the problem.

 

Hydroboost is an option. Or there are many automotive electric vacuum pumps one can get at a junkyard.

 

Master cylinder just showed up and it is definately wrong.